cover.go

Documentation: cmd/cover

     1  // Copyright 2013 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package main
     6  
     7  import (
     8  	"bytes"
     9  	"cmd/internal/cov/covcmd"
    10  	"encoding/json"
    11  	"flag"
    12  	"fmt"
    13  	"go/ast"
    14  	"go/parser"
    15  	"go/token"
    16  	"internal/coverage"
    17  	"internal/coverage/encodemeta"
    18  	"internal/coverage/slicewriter"
    19  	"io"
    20  	"log"
    21  	"os"
    22  	"path/filepath"
    23  	"sort"
    24  	"strconv"
    25  	"strings"
    26  
    27  	"cmd/internal/edit"
    28  	"cmd/internal/objabi"
    29  )
    30  
    31  const usageMessage = "" +
    32  	`Usage of 'go tool cover':
    33  Given a coverage profile produced by 'go test':
    34  	go test -coverprofile=c.out
    35  
    36  Open a web browser displaying annotated source code:
    37  	go tool cover -html=c.out
    38  
    39  Write out an HTML file instead of launching a web browser:
    40  	go tool cover -html=c.out -o coverage.html
    41  
    42  Display coverage percentages to stdout for each function:
    43  	go tool cover -func=c.out
    44  
    45  Finally, to generate modified source code with coverage annotations
    46  for a package (what go test -cover does):
    47  	go tool cover -mode=set -var=CoverageVariableName \
    48  		-pkgcfg=<config> -outfilelist=<file> file1.go ... fileN.go
    49  
    50  where -pkgcfg points to a file containing the package path,
    51  package name, module path, and related info from "go build",
    52  and -outfilelist points to a file containing the filenames
    53  of the instrumented output files (one per input file).
    54  See https://pkg.go.dev/cmd/internal/cov/covcmd#CoverPkgConfig for
    55  more on the package config.
    56  `
    57  
    58  func usage() {
    59  	fmt.Fprint(os.Stderr, usageMessage)
    60  	fmt.Fprintln(os.Stderr, "\nFlags:")
    61  	flag.PrintDefaults()
    62  	fmt.Fprintln(os.Stderr, "\n  Only one of -html, -func, or -mode may be set.")
    63  	os.Exit(2)
    64  }
    65  
    66  var (
    67  	mode             = flag.String("mode", "", "coverage mode: set, count, atomic")
    68  	varVar           = flag.String("var", "GoCover", "name of coverage variable to generate")
    69  	output           = flag.String("o", "", "file for output")
    70  	outfilelist      = flag.String("outfilelist", "", "file containing list of output files (one per line) if -pkgcfg is in use")
    71  	htmlOut          = flag.String("html", "", "generate HTML representation of coverage profile")
    72  	funcOut          = flag.String("func", "", "output coverage profile information for each function")
    73  	pkgcfg           = flag.String("pkgcfg", "", "enable full-package instrumentation mode using params from specified config file")
    74  	pkgconfig        covcmd.CoverPkgConfig
    75  	outputfiles      []string // list of *.cover.go instrumented outputs to write, one per input (set when -pkgcfg is in use)
    76  	profile          string   // The profile to read; the value of -html or -func
    77  	counterStmt      func(*File, string) string
    78  	covervarsoutfile string // an additional Go source file into which we'll write definitions of coverage counter variables + meta data variables (set when -pkgcfg is in use).
    79  	cmode            coverage.CounterMode
    80  	cgran            coverage.CounterGranularity
    81  )
    82  
    83  const (
    84  	atomicPackagePath = "sync/atomic"
    85  	atomicPackageName = "_cover_atomic_"
    86  )
    87  
    88  func main() {
    89  	objabi.AddVersionFlag()
    90  	flag.Usage = usage
    91  	objabi.Flagparse(usage)
    92  
    93  	// Usage information when no arguments.
    94  	if flag.NFlag() == 0 && flag.NArg() == 0 {
    95  		flag.Usage()
    96  	}
    97  
    98  	err := parseFlags()
    99  	if err != nil {
   100  		fmt.Fprintln(os.Stderr, err)
   101  		fmt.Fprintln(os.Stderr, `For usage information, run "go tool cover -help"`)
   102  		os.Exit(2)
   103  	}
   104  
   105  	// Generate coverage-annotated source.
   106  	if *mode != "" {
   107  		annotate(flag.Args())
   108  		return
   109  	}
   110  
   111  	// Output HTML or function coverage information.
   112  	if *htmlOut != "" {
   113  		err = htmlOutput(profile, *output)
   114  	} else {
   115  		err = funcOutput(profile, *output)
   116  	}
   117  
   118  	if err != nil {
   119  		fmt.Fprintf(os.Stderr, "cover: %v\n", err)
   120  		os.Exit(2)
   121  	}
   122  }
   123  
   124  // parseFlags sets the profile and counterStmt globals and performs validations.
   125  func parseFlags() error {
   126  	profile = *htmlOut
   127  	if *funcOut != "" {
   128  		if profile != "" {
   129  			return fmt.Errorf("too many options")
   130  		}
   131  		profile = *funcOut
   132  	}
   133  
   134  	// Must either display a profile or rewrite Go source.
   135  	if (profile == "") == (*mode == "") {
   136  		return fmt.Errorf("too many options")
   137  	}
   138  
   139  	if *varVar != "" && !token.IsIdentifier(*varVar) {
   140  		return fmt.Errorf("-var: %q is not a valid identifier", *varVar)
   141  	}
   142  
   143  	if *mode != "" {
   144  		switch *mode {
   145  		case "set":
   146  			counterStmt = setCounterStmt
   147  			cmode = coverage.CtrModeSet
   148  		case "count":
   149  			counterStmt = incCounterStmt
   150  			cmode = coverage.CtrModeCount
   151  		case "atomic":
   152  			counterStmt = atomicCounterStmt
   153  			cmode = coverage.CtrModeAtomic
   154  		case "regonly":
   155  			counterStmt = nil
   156  			cmode = coverage.CtrModeRegOnly
   157  		case "testmain":
   158  			counterStmt = nil
   159  			cmode = coverage.CtrModeTestMain
   160  		default:
   161  			return fmt.Errorf("unknown -mode %v", *mode)
   162  		}
   163  
   164  		if flag.NArg() == 0 {
   165  			return fmt.Errorf("missing source file(s)")
   166  		} else {
   167  			if *pkgcfg != "" {
   168  				if *output != "" {
   169  					return fmt.Errorf("please use '-outfilelist' flag instead of '-o'")
   170  				}
   171  				var err error
   172  				if outputfiles, err = readOutFileList(*outfilelist); err != nil {
   173  					return err
   174  				}
   175  				covervarsoutfile = outputfiles[0]
   176  				outputfiles = outputfiles[1:]
   177  				numInputs := len(flag.Args())
   178  				numOutputs := len(outputfiles)
   179  				if numOutputs != numInputs {
   180  					return fmt.Errorf("number of output files (%d) not equal to number of input files (%d)", numOutputs, numInputs)
   181  				}
   182  				if err := readPackageConfig(*pkgcfg); err != nil {
   183  					return err
   184  				}
   185  				return nil
   186  			} else {
   187  				if *outfilelist != "" {
   188  					return fmt.Errorf("'-outfilelist' flag applicable only when -pkgcfg used")
   189  				}
   190  			}
   191  			if flag.NArg() == 1 {
   192  				return nil
   193  			}
   194  		}
   195  	} else if flag.NArg() == 0 {
   196  		return nil
   197  	}
   198  	return fmt.Errorf("too many arguments")
   199  }
   200  
   201  func readOutFileList(path string) ([]string, error) {
   202  	data, err := os.ReadFile(path)
   203  	if err != nil {
   204  		return nil, fmt.Errorf("error reading -outfilelist file %q: %v", path, err)
   205  	}
   206  	return strings.Split(strings.TrimSpace(string(data)), "\n"), nil
   207  }
   208  
   209  func readPackageConfig(path string) error {
   210  	data, err := os.ReadFile(path)
   211  	if err != nil {
   212  		return fmt.Errorf("error reading pkgconfig file %q: %v", path, err)
   213  	}
   214  	if err := json.Unmarshal(data, &pkgconfig); err != nil {
   215  		return fmt.Errorf("error reading pkgconfig file %q: %v", path, err)
   216  	}
   217  	switch pkgconfig.Granularity {
   218  	case "perblock":
   219  		cgran = coverage.CtrGranularityPerBlock
   220  	case "perfunc":
   221  		cgran = coverage.CtrGranularityPerFunc
   222  	default:
   223  		return fmt.Errorf(`%s: pkgconfig requires perblock/perfunc value`, path)
   224  	}
   225  	return nil
   226  }
   227  
   228  // Block represents the information about a basic block to be recorded in the analysis.
   229  // Note: Our definition of basic block is based on control structures; we don't break
   230  // apart && and ||. We could but it doesn't seem important enough to bother.
   231  type Block struct {
   232  	startByte token.Pos
   233  	endByte   token.Pos
   234  	numStmt   int
   235  }
   236  
   237  // Package holds package-specific state.
   238  type Package struct {
   239  	mdb            *encodemeta.CoverageMetaDataBuilder
   240  	counterLengths []int
   241  }
   242  
   243  // Function holds func-specific state.
   244  type Func struct {
   245  	units      []coverage.CoverableUnit
   246  	counterVar string
   247  }
   248  
   249  // File is a wrapper for the state of a file used in the parser.
   250  // The basic parse tree walker is a method of this type.
   251  type File struct {
   252  	fset    *token.FileSet
   253  	name    string // Name of file.
   254  	astFile *ast.File
   255  	blocks  []Block
   256  	content []byte
   257  	edit    *edit.Buffer
   258  	mdb     *encodemeta.CoverageMetaDataBuilder
   259  	fn      Func
   260  	pkg     *Package
   261  }
   262  
   263  // findText finds text in the original source, starting at pos.
   264  // It correctly skips over comments and assumes it need not
   265  // handle quoted strings.
   266  // It returns a byte offset within f.src.
   267  func (f *File) findText(pos token.Pos, text string) int {
   268  	b := []byte(text)
   269  	start := f.offset(pos)
   270  	i := start
   271  	s := f.content
   272  	for i < len(s) {
   273  		if bytes.HasPrefix(s[i:], b) {
   274  			return i
   275  		}
   276  		if i+2 <= len(s) && s[i] == '/' && s[i+1] == '/' {
   277  			for i < len(s) && s[i] != '\n' {
   278  				i++
   279  			}
   280  			continue
   281  		}
   282  		if i+2 <= len(s) && s[i] == '/' && s[i+1] == '*' {
   283  			for i += 2; ; i++ {
   284  				if i+2 > len(s) {
   285  					return 0
   286  				}
   287  				if s[i] == '*' && s[i+1] == '/' {
   288  					i += 2
   289  					break
   290  				}
   291  			}
   292  			continue
   293  		}
   294  		i++
   295  	}
   296  	return -1
   297  }
   298  
   299  // Visit implements the ast.Visitor interface.
   300  func (f *File) Visit(node ast.Node) ast.Visitor {
   301  	switch n := node.(type) {
   302  	case *ast.BlockStmt:
   303  		// If it's a switch or select, the body is a list of case clauses; don't tag the block itself.
   304  		if len(n.List) > 0 {
   305  			switch n.List[0].(type) {
   306  			case *ast.CaseClause: // switch
   307  				for _, n := range n.List {
   308  					clause := n.(*ast.CaseClause)
   309  					f.addCounters(clause.Colon+1, clause.Colon+1, clause.End(), clause.Body, false)
   310  				}
   311  				return f
   312  			case *ast.CommClause: // select
   313  				for _, n := range n.List {
   314  					clause := n.(*ast.CommClause)
   315  					f.addCounters(clause.Colon+1, clause.Colon+1, clause.End(), clause.Body, false)
   316  				}
   317  				return f
   318  			}
   319  		}
   320  		f.addCounters(n.Lbrace, n.Lbrace+1, n.Rbrace+1, n.List, true) // +1 to step past closing brace.
   321  	case *ast.IfStmt:
   322  		if n.Init != nil {
   323  			ast.Walk(f, n.Init)
   324  		}
   325  		ast.Walk(f, n.Cond)
   326  		ast.Walk(f, n.Body)
   327  		if n.Else == nil {
   328  			return nil
   329  		}
   330  		// The elses are special, because if we have
   331  		//	if x {
   332  		//	} else if y {
   333  		//	}
   334  		// we want to cover the "if y". To do this, we need a place to drop the counter,
   335  		// so we add a hidden block:
   336  		//	if x {
   337  		//	} else {
   338  		//		if y {
   339  		//		}
   340  		//	}
   341  		elseOffset := f.findText(n.Body.End(), "else")
   342  		if elseOffset < 0 {
   343  			panic("lost else")
   344  		}
   345  		f.edit.Insert(elseOffset+4, "{")
   346  		f.edit.Insert(f.offset(n.Else.End()), "}")
   347  
   348  		// We just created a block, now walk it.
   349  		// Adjust the position of the new block to start after
   350  		// the "else". That will cause it to follow the "{"
   351  		// we inserted above.
   352  		pos := f.fset.File(n.Body.End()).Pos(elseOffset + 4)
   353  		switch stmt := n.Else.(type) {
   354  		case *ast.IfStmt:
   355  			block := &ast.BlockStmt{
   356  				Lbrace: pos,
   357  				List:   []ast.Stmt{stmt},
   358  				Rbrace: stmt.End(),
   359  			}
   360  			n.Else = block
   361  		case *ast.BlockStmt:
   362  			stmt.Lbrace = pos
   363  		default:
   364  			panic("unexpected node type in if")
   365  		}
   366  		ast.Walk(f, n.Else)
   367  		return nil
   368  	case *ast.SelectStmt:
   369  		// Don't annotate an empty select - creates a syntax error.
   370  		if n.Body == nil || len(n.Body.List) == 0 {
   371  			return nil
   372  		}
   373  	case *ast.SwitchStmt:
   374  		// Don't annotate an empty switch - creates a syntax error.
   375  		if n.Body == nil || len(n.Body.List) == 0 {
   376  			if n.Init != nil {
   377  				ast.Walk(f, n.Init)
   378  			}
   379  			if n.Tag != nil {
   380  				ast.Walk(f, n.Tag)
   381  			}
   382  			return nil
   383  		}
   384  	case *ast.TypeSwitchStmt:
   385  		// Don't annotate an empty type switch - creates a syntax error.
   386  		if n.Body == nil || len(n.Body.List) == 0 {
   387  			if n.Init != nil {
   388  				ast.Walk(f, n.Init)
   389  			}
   390  			ast.Walk(f, n.Assign)
   391  			return nil
   392  		}
   393  	case *ast.FuncDecl:
   394  		// Don't annotate functions with blank names - they cannot be executed.
   395  		// Similarly for bodyless funcs.
   396  		if n.Name.Name == "_" || n.Body == nil {
   397  			return nil
   398  		}
   399  		fname := n.Name.Name
   400  		// Skip AddUint32 and StoreUint32 if we're instrumenting
   401  		// sync/atomic itself in atomic mode (out of an abundance of
   402  		// caution), since as part of the instrumentation process we
   403  		// add calls to AddUint32/StoreUint32, and we don't want to
   404  		// somehow create an infinite loop.
   405  		//
   406  		// Note that in the current implementation (Go 1.20) both
   407  		// routines are assembly stubs that forward calls to the
   408  		// runtime/internal/atomic equivalents, hence the infinite
   409  		// loop scenario is purely theoretical (maybe if in some
   410  		// future implementation one of these functions might be
   411  		// written in Go). See #57445 for more details.
   412  		if atomicOnAtomic() && (fname == "AddUint32" || fname == "StoreUint32") {
   413  			return nil
   414  		}
   415  		// Determine proper function or method name.
   416  		if r := n.Recv; r != nil && len(r.List) == 1 {
   417  			t := r.List[0].Type
   418  			star := ""
   419  			if p, _ := t.(*ast.StarExpr); p != nil {
   420  				t = p.X
   421  				star = "*"
   422  			}
   423  			if p, _ := t.(*ast.Ident); p != nil {
   424  				fname = star + p.Name + "." + fname
   425  			}
   426  		}
   427  		walkBody := true
   428  		if *pkgcfg != "" {
   429  			f.preFunc(n, fname)
   430  			if pkgconfig.Granularity == "perfunc" {
   431  				walkBody = false
   432  			}
   433  		}
   434  		if walkBody {
   435  			ast.Walk(f, n.Body)
   436  		}
   437  		if *pkgcfg != "" {
   438  			flit := false
   439  			f.postFunc(n, fname, flit, n.Body)
   440  		}
   441  		return nil
   442  	case *ast.FuncLit:
   443  		// For function literals enclosed in functions, just glom the
   444  		// code for the literal in with the enclosing function (for now).
   445  		if f.fn.counterVar != "" {
   446  			return f
   447  		}
   448  
   449  		// Hack: function literals aren't named in the go/ast representation,
   450  		// and we don't know what name the compiler will choose. For now,
   451  		// just make up a descriptive name.
   452  		pos := n.Pos()
   453  		p := f.fset.File(pos).Position(pos)
   454  		fname := fmt.Sprintf("func.L%d.C%d", p.Line, p.Column)
   455  		if *pkgcfg != "" {
   456  			f.preFunc(n, fname)
   457  		}
   458  		if pkgconfig.Granularity != "perfunc" {
   459  			ast.Walk(f, n.Body)
   460  		}
   461  		if *pkgcfg != "" {
   462  			flit := true
   463  			f.postFunc(n, fname, flit, n.Body)
   464  		}
   465  		return nil
   466  	}
   467  	return f
   468  }
   469  
   470  func mkCounterVarName(idx int) string {
   471  	return fmt.Sprintf("%s_%d", *varVar, idx)
   472  }
   473  
   474  func mkPackageIdVar() string {
   475  	return *varVar + "P"
   476  }
   477  
   478  func mkMetaVar() string {
   479  	return *varVar + "M"
   480  }
   481  
   482  func mkPackageIdExpression() string {
   483  	ppath := pkgconfig.PkgPath
   484  	if hcid := coverage.HardCodedPkgID(ppath); hcid != -1 {
   485  		return fmt.Sprintf("uint32(%d)", uint32(hcid))
   486  	}
   487  	return mkPackageIdVar()
   488  }
   489  
   490  func (f *File) preFunc(fn ast.Node, fname string) {
   491  	f.fn.units = f.fn.units[:0]
   492  
   493  	// create a new counter variable for this function.
   494  	cv := mkCounterVarName(len(f.pkg.counterLengths))
   495  	f.fn.counterVar = cv
   496  }
   497  
   498  func (f *File) postFunc(fn ast.Node, funcname string, flit bool, body *ast.BlockStmt) {
   499  
   500  	// Tack on single counter write if we are in "perfunc" mode.
   501  	singleCtr := ""
   502  	if pkgconfig.Granularity == "perfunc" {
   503  		singleCtr = "; " + f.newCounter(fn.Pos(), fn.Pos(), 1)
   504  	}
   505  
   506  	// record the length of the counter var required.
   507  	nc := len(f.fn.units) + coverage.FirstCtrOffset
   508  	f.pkg.counterLengths = append(f.pkg.counterLengths, nc)
   509  
   510  	// FIXME: for windows, do we want "\" and not "/"? Need to test here.
   511  	// Currently filename is formed as packagepath + "/" + basename.
   512  	fnpos := f.fset.Position(fn.Pos())
   513  	ppath := pkgconfig.PkgPath
   514  	filename := ppath + "/" + filepath.Base(fnpos.Filename)
   515  
   516  	// The convention for cmd/cover is that if the go command that
   517  	// kicks off coverage specifies a local import path (e.g. "go test
   518  	// -cover ./thispackage"), the tool will capture full pathnames
   519  	// for source files instead of relative paths, which tend to work
   520  	// more smoothly for "go tool cover -html". See also issue #56433
   521  	// for more details.
   522  	if pkgconfig.Local {
   523  		filename = f.name
   524  	}
   525  
   526  	// Hand off function to meta-data builder.
   527  	fd := coverage.FuncDesc{
   528  		Funcname: funcname,
   529  		Srcfile:  filename,
   530  		Units:    f.fn.units,
   531  		Lit:      flit,
   532  	}
   533  	funcId := f.mdb.AddFunc(fd)
   534  
   535  	hookWrite := func(cv string, which int, val string) string {
   536  		return fmt.Sprintf("%s[%d] = %s", cv, which, val)
   537  	}
   538  	if *mode == "atomic" {
   539  		hookWrite = func(cv string, which int, val string) string {
   540  			return fmt.Sprintf("%sStoreUint32(&%s[%d], %s)",
   541  				atomicPackagePrefix(), cv, which, val)
   542  		}
   543  	}
   544  
   545  	// Generate the registration hook sequence for the function. This
   546  	// sequence looks like
   547  	//
   548  	//   counterVar[0] = <num_units>
   549  	//   counterVar[1] = pkgId
   550  	//   counterVar[2] = fnId
   551  	//
   552  	cv := f.fn.counterVar
   553  	regHook := hookWrite(cv, 0, strconv.Itoa(len(f.fn.units))) + " ; " +
   554  		hookWrite(cv, 1, mkPackageIdExpression()) + " ; " +
   555  		hookWrite(cv, 2, strconv.Itoa(int(funcId))) + singleCtr
   556  
   557  	// Insert the registration sequence into the function. We want this sequence to
   558  	// appear before any counter updates, so use a hack to ensure that this edit
   559  	// applies before the edit corresponding to the prolog counter update.
   560  
   561  	boff := f.offset(body.Pos())
   562  	ipos := f.fset.File(body.Pos()).Pos(boff)
   563  	ip := f.offset(ipos)
   564  	f.edit.Replace(ip, ip+1, string(f.content[ipos-1])+regHook+" ; ")
   565  
   566  	f.fn.counterVar = ""
   567  }
   568  
   569  func annotate(names []string) {
   570  	var p *Package
   571  	if *pkgcfg != "" {
   572  		pp := pkgconfig.PkgPath
   573  		pn := pkgconfig.PkgName
   574  		mp := pkgconfig.ModulePath
   575  		mdb, err := encodemeta.NewCoverageMetaDataBuilder(pp, pn, mp)
   576  		if err != nil {
   577  			log.Fatalf("creating coverage meta-data builder: %v\n", err)
   578  		}
   579  		p = &Package{
   580  			mdb: mdb,
   581  		}
   582  	}
   583  	// TODO: process files in parallel here if it matters.
   584  	for k, name := range names {
   585  		if strings.ContainsAny(name, "\r\n") {
   586  			// annotateFile uses '//line' directives, which don't permit newlines.
   587  			log.Fatalf("cover: input path contains newline character: %q", name)
   588  		}
   589  
   590  		fd := os.Stdout
   591  		isStdout := true
   592  		if *pkgcfg != "" {
   593  			var err error
   594  			fd, err = os.Create(outputfiles[k])
   595  			if err != nil {
   596  				log.Fatalf("cover: %s", err)
   597  			}
   598  			isStdout = false
   599  		} else if *output != "" {
   600  			var err error
   601  			fd, err = os.Create(*output)
   602  			if err != nil {
   603  				log.Fatalf("cover: %s", err)
   604  			}
   605  			isStdout = false
   606  		}
   607  		p.annotateFile(name, fd)
   608  		if !isStdout {
   609  			if err := fd.Close(); err != nil {
   610  				log.Fatalf("cover: %s", err)
   611  			}
   612  		}
   613  	}
   614  
   615  	if *pkgcfg != "" {
   616  		fd, err := os.Create(covervarsoutfile)
   617  		if err != nil {
   618  			log.Fatalf("cover: %s", err)
   619  		}
   620  		p.emitMetaData(fd)
   621  		if err := fd.Close(); err != nil {
   622  			log.Fatalf("cover: %s", err)
   623  		}
   624  	}
   625  }
   626  
   627  func (p *Package) annotateFile(name string, fd io.Writer) {
   628  	fset := token.NewFileSet()
   629  	content, err := os.ReadFile(name)
   630  	if err != nil {
   631  		log.Fatalf("cover: %s: %s", name, err)
   632  	}
   633  	parsedFile, err := parser.ParseFile(fset, name, content, parser.ParseComments)
   634  	if err != nil {
   635  		log.Fatalf("cover: %s: %s", name, err)
   636  	}
   637  
   638  	file := &File{
   639  		fset:    fset,
   640  		name:    name,
   641  		content: content,
   642  		edit:    edit.NewBuffer(content),
   643  		astFile: parsedFile,
   644  	}
   645  	if p != nil {
   646  		file.mdb = p.mdb
   647  		file.pkg = p
   648  	}
   649  
   650  	if *mode == "atomic" {
   651  		// Add import of sync/atomic immediately after package clause.
   652  		// We do this even if there is an existing import, because the
   653  		// existing import may be shadowed at any given place we want
   654  		// to refer to it, and our name (_cover_atomic_) is less likely to
   655  		// be shadowed. The one exception is if we're visiting the
   656  		// sync/atomic package itself, in which case we can refer to
   657  		// functions directly without an import prefix. See also #57445.
   658  		if pkgconfig.PkgPath != "sync/atomic" {
   659  			file.edit.Insert(file.offset(file.astFile.Name.End()),
   660  				fmt.Sprintf("; import %s %q", atomicPackageName, atomicPackagePath))
   661  		}
   662  	}
   663  	if pkgconfig.PkgName == "main" {
   664  		file.edit.Insert(file.offset(file.astFile.Name.End()),
   665  			"; import _ \"runtime/coverage\"")
   666  	}
   667  
   668  	if counterStmt != nil {
   669  		ast.Walk(file, file.astFile)
   670  	}
   671  	newContent := file.edit.Bytes()
   672  
   673  	if strings.ContainsAny(name, "\r\n") {
   674  		// This should have been checked by the caller already, but we double check
   675  		// here just to be sure we haven't missed a caller somewhere.
   676  		panic(fmt.Sprintf("annotateFile: name contains unexpected newline character: %q", name))
   677  	}
   678  	fmt.Fprintf(fd, "//line %s:1:1\n", name)
   679  	fd.Write(newContent)
   680  
   681  	// After printing the source tree, add some declarations for the
   682  	// counters etc. We could do this by adding to the tree, but it's
   683  	// easier just to print the text.
   684  	file.addVariables(fd)
   685  
   686  	// Emit a reference to the atomic package to avoid
   687  	// import and not used error when there's no code in a file.
   688  	if *mode == "atomic" {
   689  		fmt.Fprintf(fd, "\nvar _ = %sLoadUint32\n", atomicPackagePrefix())
   690  	}
   691  }
   692  
   693  // setCounterStmt returns the expression: __count[23] = 1.
   694  func setCounterStmt(f *File, counter string) string {
   695  	return fmt.Sprintf("%s = 1", counter)
   696  }
   697  
   698  // incCounterStmt returns the expression: __count[23]++.
   699  func incCounterStmt(f *File, counter string) string {
   700  	return fmt.Sprintf("%s++", counter)
   701  }
   702  
   703  // atomicCounterStmt returns the expression: atomic.AddUint32(&__count[23], 1)
   704  func atomicCounterStmt(f *File, counter string) string {
   705  	return fmt.Sprintf("%sAddUint32(&%s, 1)", atomicPackagePrefix(), counter)
   706  }
   707  
   708  // newCounter creates a new counter expression of the appropriate form.
   709  func (f *File) newCounter(start, end token.Pos, numStmt int) string {
   710  	var stmt string
   711  	if *pkgcfg != "" {
   712  		slot := len(f.fn.units) + coverage.FirstCtrOffset
   713  		if f.fn.counterVar == "" {
   714  			panic("internal error: counter var unset")
   715  		}
   716  		stmt = counterStmt(f, fmt.Sprintf("%s[%d]", f.fn.counterVar, slot))
   717  		stpos := f.fset.Position(start)
   718  		enpos := f.fset.Position(end)
   719  		stpos, enpos = dedup(stpos, enpos)
   720  		unit := coverage.CoverableUnit{
   721  			StLine:  uint32(stpos.Line),
   722  			StCol:   uint32(stpos.Column),
   723  			EnLine:  uint32(enpos.Line),
   724  			EnCol:   uint32(enpos.Column),
   725  			NxStmts: uint32(numStmt),
   726  		}
   727  		f.fn.units = append(f.fn.units, unit)
   728  	} else {
   729  		stmt = counterStmt(f, fmt.Sprintf("%s.Count[%d]", *varVar,
   730  			len(f.blocks)))
   731  		f.blocks = append(f.blocks, Block{start, end, numStmt})
   732  	}
   733  	return stmt
   734  }
   735  
   736  // addCounters takes a list of statements and adds counters to the beginning of
   737  // each basic block at the top level of that list. For instance, given
   738  //
   739  //	S1
   740  //	if cond {
   741  //		S2
   742  //	}
   743  //	S3
   744  //
   745  // counters will be added before S1 and before S3. The block containing S2
   746  // will be visited in a separate call.
   747  // TODO: Nested simple blocks get unnecessary (but correct) counters
   748  func (f *File) addCounters(pos, insertPos, blockEnd token.Pos, list []ast.Stmt, extendToClosingBrace bool) {
   749  	// Special case: make sure we add a counter to an empty block. Can't do this below
   750  	// or we will add a counter to an empty statement list after, say, a return statement.
   751  	if len(list) == 0 {
   752  		f.edit.Insert(f.offset(insertPos), f.newCounter(insertPos, blockEnd, 0)+";")
   753  		return
   754  	}
   755  	// Make a copy of the list, as we may mutate it and should leave the
   756  	// existing list intact.
   757  	list = append([]ast.Stmt(nil), list...)
   758  	// We have a block (statement list), but it may have several basic blocks due to the
   759  	// appearance of statements that affect the flow of control.
   760  	for {
   761  		// Find first statement that affects flow of control (break, continue, if, etc.).
   762  		// It will be the last statement of this basic block.
   763  		var last int
   764  		end := blockEnd
   765  		for last = 0; last < len(list); last++ {
   766  			stmt := list[last]
   767  			end = f.statementBoundary(stmt)
   768  			if f.endsBasicSourceBlock(stmt) {
   769  				// If it is a labeled statement, we need to place a counter between
   770  				// the label and its statement because it may be the target of a goto
   771  				// and thus start a basic block. That is, given
   772  				//	foo: stmt
   773  				// we need to create
   774  				//	foo: ; stmt
   775  				// and mark the label as a block-terminating statement.
   776  				// The result will then be
   777  				//	foo: COUNTER[n]++; stmt
   778  				// However, we can't do this if the labeled statement is already
   779  				// a control statement, such as a labeled for.
   780  				if label, isLabel := stmt.(*ast.LabeledStmt); isLabel && !f.isControl(label.Stmt) {
   781  					newLabel := *label
   782  					newLabel.Stmt = &ast.EmptyStmt{
   783  						Semicolon: label.Stmt.Pos(),
   784  						Implicit:  true,
   785  					}
   786  					end = label.Pos() // Previous block ends before the label.
   787  					list[last] = &newLabel
   788  					// Open a gap and drop in the old statement, now without a label.
   789  					list = append(list, nil)
   790  					copy(list[last+1:], list[last:])
   791  					list[last+1] = label.Stmt
   792  				}
   793  				last++
   794  				extendToClosingBrace = false // Block is broken up now.
   795  				break
   796  			}
   797  		}
   798  		if extendToClosingBrace {
   799  			end = blockEnd
   800  		}
   801  		if pos != end { // Can have no source to cover if e.g. blocks abut.
   802  			f.edit.Insert(f.offset(insertPos), f.newCounter(pos, end, last)+";")
   803  		}
   804  		list = list[last:]
   805  		if len(list) == 0 {
   806  			break
   807  		}
   808  		pos = list[0].Pos()
   809  		insertPos = pos
   810  	}
   811  }
   812  
   813  // hasFuncLiteral reports the existence and position of the first func literal
   814  // in the node, if any. If a func literal appears, it usually marks the termination
   815  // of a basic block because the function body is itself a block.
   816  // Therefore we draw a line at the start of the body of the first function literal we find.
   817  // TODO: what if there's more than one? Probably doesn't matter much.
   818  func hasFuncLiteral(n ast.Node) (bool, token.Pos) {
   819  	if n == nil {
   820  		return false, 0
   821  	}
   822  	var literal funcLitFinder
   823  	ast.Walk(&literal, n)
   824  	return literal.found(), token.Pos(literal)
   825  }
   826  
   827  // statementBoundary finds the location in s that terminates the current basic
   828  // block in the source.
   829  func (f *File) statementBoundary(s ast.Stmt) token.Pos {
   830  	// Control flow statements are easy.
   831  	switch s := s.(type) {
   832  	case *ast.BlockStmt:
   833  		// Treat blocks like basic blocks to avoid overlapping counters.
   834  		return s.Lbrace
   835  	case *ast.IfStmt:
   836  		found, pos := hasFuncLiteral(s.Init)
   837  		if found {
   838  			return pos
   839  		}
   840  		found, pos = hasFuncLiteral(s.Cond)
   841  		if found {
   842  			return pos
   843  		}
   844  		return s.Body.Lbrace
   845  	case *ast.ForStmt:
   846  		found, pos := hasFuncLiteral(s.Init)
   847  		if found {
   848  			return pos
   849  		}
   850  		found, pos = hasFuncLiteral(s.Cond)
   851  		if found {
   852  			return pos
   853  		}
   854  		found, pos = hasFuncLiteral(s.Post)
   855  		if found {
   856  			return pos
   857  		}
   858  		return s.Body.Lbrace
   859  	case *ast.LabeledStmt:
   860  		return f.statementBoundary(s.Stmt)
   861  	case *ast.RangeStmt:
   862  		found, pos := hasFuncLiteral(s.X)
   863  		if found {
   864  			return pos
   865  		}
   866  		return s.Body.Lbrace
   867  	case *ast.SwitchStmt:
   868  		found, pos := hasFuncLiteral(s.Init)
   869  		if found {
   870  			return pos
   871  		}
   872  		found, pos = hasFuncLiteral(s.Tag)
   873  		if found {
   874  			return pos
   875  		}
   876  		return s.Body.Lbrace
   877  	case *ast.SelectStmt:
   878  		return s.Body.Lbrace
   879  	case *ast.TypeSwitchStmt:
   880  		found, pos := hasFuncLiteral(s.Init)
   881  		if found {
   882  			return pos
   883  		}
   884  		return s.Body.Lbrace
   885  	}
   886  	// If not a control flow statement, it is a declaration, expression, call, etc. and it may have a function literal.
   887  	// If it does, that's tricky because we want to exclude the body of the function from this block.
   888  	// Draw a line at the start of the body of the first function literal we find.
   889  	// TODO: what if there's more than one? Probably doesn't matter much.
   890  	found, pos := hasFuncLiteral(s)
   891  	if found {
   892  		return pos
   893  	}
   894  	return s.End()
   895  }
   896  
   897  // endsBasicSourceBlock reports whether s changes the flow of control: break, if, etc.,
   898  // or if it's just problematic, for instance contains a function literal, which will complicate
   899  // accounting due to the block-within-an expression.
   900  func (f *File) endsBasicSourceBlock(s ast.Stmt) bool {
   901  	switch s := s.(type) {
   902  	case *ast.BlockStmt:
   903  		// Treat blocks like basic blocks to avoid overlapping counters.
   904  		return true
   905  	case *ast.BranchStmt:
   906  		return true
   907  	case *ast.ForStmt:
   908  		return true
   909  	case *ast.IfStmt:
   910  		return true
   911  	case *ast.LabeledStmt:
   912  		return true // A goto may branch here, starting a new basic block.
   913  	case *ast.RangeStmt:
   914  		return true
   915  	case *ast.SwitchStmt:
   916  		return true
   917  	case *ast.SelectStmt:
   918  		return true
   919  	case *ast.TypeSwitchStmt:
   920  		return true
   921  	case *ast.ExprStmt:
   922  		// Calls to panic change the flow.
   923  		// We really should verify that "panic" is the predefined function,
   924  		// but without type checking we can't and the likelihood of it being
   925  		// an actual problem is vanishingly small.
   926  		if call, ok := s.X.(*ast.CallExpr); ok {
   927  			if ident, ok := call.Fun.(*ast.Ident); ok && ident.Name == "panic" && len(call.Args) == 1 {
   928  				return true
   929  			}
   930  		}
   931  	}
   932  	found, _ := hasFuncLiteral(s)
   933  	return found
   934  }
   935  
   936  // isControl reports whether s is a control statement that, if labeled, cannot be
   937  // separated from its label.
   938  func (f *File) isControl(s ast.Stmt) bool {
   939  	switch s.(type) {
   940  	case *ast.ForStmt, *ast.RangeStmt, *ast.SwitchStmt, *ast.SelectStmt, *ast.TypeSwitchStmt:
   941  		return true
   942  	}
   943  	return false
   944  }
   945  
   946  // funcLitFinder implements the ast.Visitor pattern to find the location of any
   947  // function literal in a subtree.
   948  type funcLitFinder token.Pos
   949  
   950  func (f *funcLitFinder) Visit(node ast.Node) (w ast.Visitor) {
   951  	if f.found() {
   952  		return nil // Prune search.
   953  	}
   954  	switch n := node.(type) {
   955  	case *ast.FuncLit:
   956  		*f = funcLitFinder(n.Body.Lbrace)
   957  		return nil // Prune search.
   958  	}
   959  	return f
   960  }
   961  
   962  func (f *funcLitFinder) found() bool {
   963  	return token.Pos(*f) != token.NoPos
   964  }
   965  
   966  // Sort interface for []block1; used for self-check in addVariables.
   967  
   968  type block1 struct {
   969  	Block
   970  	index int
   971  }
   972  
   973  type blockSlice []block1
   974  
   975  func (b blockSlice) Len() int           { return len(b) }
   976  func (b blockSlice) Less(i, j int) bool { return b[i].startByte < b[j].startByte }
   977  func (b blockSlice) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
   978  
   979  // offset translates a token position into a 0-indexed byte offset.
   980  func (f *File) offset(pos token.Pos) int {
   981  	return f.fset.Position(pos).Offset
   982  }
   983  
   984  // addVariables adds to the end of the file the declarations to set up the counter and position variables.
   985  func (f *File) addVariables(w io.Writer) {
   986  	if *pkgcfg != "" {
   987  		return
   988  	}
   989  	// Self-check: Verify that the instrumented basic blocks are disjoint.
   990  	t := make([]block1, len(f.blocks))
   991  	for i := range f.blocks {
   992  		t[i].Block = f.blocks[i]
   993  		t[i].index = i
   994  	}
   995  	sort.Sort(blockSlice(t))
   996  	for i := 1; i < len(t); i++ {
   997  		if t[i-1].endByte > t[i].startByte {
   998  			fmt.Fprintf(os.Stderr, "cover: internal error: block %d overlaps block %d\n", t[i-1].index, t[i].index)
   999  			// Note: error message is in byte positions, not token positions.
  1000  			fmt.Fprintf(os.Stderr, "\t%s:#%d,#%d %s:#%d,#%d\n",
  1001  				f.name, f.offset(t[i-1].startByte), f.offset(t[i-1].endByte),
  1002  				f.name, f.offset(t[i].startByte), f.offset(t[i].endByte))
  1003  		}
  1004  	}
  1005  
  1006  	// Declare the coverage struct as a package-level variable.
  1007  	fmt.Fprintf(w, "\nvar %s = struct {\n", *varVar)
  1008  	fmt.Fprintf(w, "\tCount     [%d]uint32\n", len(f.blocks))
  1009  	fmt.Fprintf(w, "\tPos       [3 * %d]uint32\n", len(f.blocks))
  1010  	fmt.Fprintf(w, "\tNumStmt   [%d]uint16\n", len(f.blocks))
  1011  	fmt.Fprintf(w, "} {\n")
  1012  
  1013  	// Initialize the position array field.
  1014  	fmt.Fprintf(w, "\tPos: [3 * %d]uint32{\n", len(f.blocks))
  1015  
  1016  	// A nice long list of positions. Each position is encoded as follows to reduce size:
  1017  	// - 32-bit starting line number
  1018  	// - 32-bit ending line number
  1019  	// - (16 bit ending column number << 16) | (16-bit starting column number).
  1020  	for i, block := range f.blocks {
  1021  		start := f.fset.Position(block.startByte)
  1022  		end := f.fset.Position(block.endByte)
  1023  
  1024  		start, end = dedup(start, end)
  1025  
  1026  		fmt.Fprintf(w, "\t\t%d, %d, %#x, // [%d]\n", start.Line, end.Line, (end.Column&0xFFFF)<<16|(start.Column&0xFFFF), i)
  1027  	}
  1028  
  1029  	// Close the position array.
  1030  	fmt.Fprintf(w, "\t},\n")
  1031  
  1032  	// Initialize the position array field.
  1033  	fmt.Fprintf(w, "\tNumStmt: [%d]uint16{\n", len(f.blocks))
  1034  
  1035  	// A nice long list of statements-per-block, so we can give a conventional
  1036  	// valuation of "percent covered". To save space, it's a 16-bit number, so we
  1037  	// clamp it if it overflows - won't matter in practice.
  1038  	for i, block := range f.blocks {
  1039  		n := block.numStmt
  1040  		if n > 1<<16-1 {
  1041  			n = 1<<16 - 1
  1042  		}
  1043  		fmt.Fprintf(w, "\t\t%d, // %d\n", n, i)
  1044  	}
  1045  
  1046  	// Close the statements-per-block array.
  1047  	fmt.Fprintf(w, "\t},\n")
  1048  
  1049  	// Close the struct initialization.
  1050  	fmt.Fprintf(w, "}\n")
  1051  }
  1052  
  1053  // It is possible for positions to repeat when there is a line
  1054  // directive that does not specify column information and the input
  1055  // has not been passed through gofmt.
  1056  // See issues #27530 and #30746.
  1057  // Tests are TestHtmlUnformatted and TestLineDup.
  1058  // We use a map to avoid duplicates.
  1059  
  1060  // pos2 is a pair of token.Position values, used as a map key type.
  1061  type pos2 struct {
  1062  	p1, p2 token.Position
  1063  }
  1064  
  1065  // seenPos2 tracks whether we have seen a token.Position pair.
  1066  var seenPos2 = make(map[pos2]bool)
  1067  
  1068  // dedup takes a token.Position pair and returns a pair that does not
  1069  // duplicate any existing pair. The returned pair will have the Offset
  1070  // fields cleared.
  1071  func dedup(p1, p2 token.Position) (r1, r2 token.Position) {
  1072  	key := pos2{
  1073  		p1: p1,
  1074  		p2: p2,
  1075  	}
  1076  
  1077  	// We want to ignore the Offset fields in the map,
  1078  	// since cover uses only file/line/column.
  1079  	key.p1.Offset = 0
  1080  	key.p2.Offset = 0
  1081  
  1082  	for seenPos2[key] {
  1083  		key.p2.Column++
  1084  	}
  1085  	seenPos2[key] = true
  1086  
  1087  	return key.p1, key.p2
  1088  }
  1089  
  1090  func (p *Package) emitMetaData(w io.Writer) {
  1091  	if *pkgcfg == "" {
  1092  		return
  1093  	}
  1094  
  1095  	// If the "EmitMetaFile" path has been set, invoke a helper
  1096  	// that will write out a pre-cooked meta-data file for this package
  1097  	// to the specified location, in effect simulating the execution
  1098  	// of a test binary that doesn't do any testing to speak of.
  1099  	if pkgconfig.EmitMetaFile != "" {
  1100  		p.emitMetaFile(pkgconfig.EmitMetaFile)
  1101  	}
  1102  
  1103  	// Something went wrong if regonly/testmain mode is in effect and
  1104  	// we have instrumented functions.
  1105  	if counterStmt == nil && len(p.counterLengths) != 0 {
  1106  		panic("internal error: seen functions with regonly/testmain")
  1107  	}
  1108  
  1109  	// Emit package name.
  1110  	fmt.Fprintf(w, "\npackage %s\n\n", pkgconfig.PkgName)
  1111  
  1112  	// Emit package ID var.
  1113  	fmt.Fprintf(w, "\nvar %sP uint32\n", *varVar)
  1114  
  1115  	// Emit all of the counter variables.
  1116  	for k := range p.counterLengths {
  1117  		cvn := mkCounterVarName(k)
  1118  		fmt.Fprintf(w, "var %s [%d]uint32\n", cvn, p.counterLengths[k])
  1119  	}
  1120  
  1121  	// Emit encoded meta-data.
  1122  	var sws slicewriter.WriteSeeker
  1123  	digest, err := p.mdb.Emit(&sws)
  1124  	if err != nil {
  1125  		log.Fatalf("encoding meta-data: %v", err)
  1126  	}
  1127  	p.mdb = nil
  1128  	fmt.Fprintf(w, "var %s = [...]byte{\n", mkMetaVar())
  1129  	payload := sws.BytesWritten()
  1130  	for k, b := range payload {
  1131  		fmt.Fprintf(w, " 0x%x,", b)
  1132  		if k != 0 && k%8 == 0 {
  1133  			fmt.Fprintf(w, "\n")
  1134  		}
  1135  	}
  1136  	fmt.Fprintf(w, "}\n")
  1137  
  1138  	fixcfg := covcmd.CoverFixupConfig{
  1139  		Strategy:           "normal",
  1140  		MetaVar:            mkMetaVar(),
  1141  		MetaLen:            len(payload),
  1142  		MetaHash:           fmt.Sprintf("%x", digest),
  1143  		PkgIdVar:           mkPackageIdVar(),
  1144  		CounterPrefix:      *varVar,
  1145  		CounterGranularity: pkgconfig.Granularity,
  1146  		CounterMode:        *mode,
  1147  	}
  1148  	fixdata, err := json.Marshal(fixcfg)
  1149  	if err != nil {
  1150  		log.Fatalf("marshal fixupcfg: %v", err)
  1151  	}
  1152  	if err := os.WriteFile(pkgconfig.OutConfig, fixdata, 0666); err != nil {
  1153  		log.Fatalf("error writing %s: %v", pkgconfig.OutConfig, err)
  1154  	}
  1155  }
  1156  
  1157  // atomicOnAtomic returns true if we're instrumenting
  1158  // the sync/atomic package AND using atomic mode.
  1159  func atomicOnAtomic() bool {
  1160  	return *mode == "atomic" && pkgconfig.PkgPath == "sync/atomic"
  1161  }
  1162  
  1163  // atomicPackagePrefix returns the import path prefix used to refer to
  1164  // our special import of sync/atomic; this is either set to the
  1165  // constant atomicPackageName plus a dot or the empty string if we're
  1166  // instrumenting the sync/atomic package itself.
  1167  func atomicPackagePrefix() string {
  1168  	if atomicOnAtomic() {
  1169  		return ""
  1170  	}
  1171  	return atomicPackageName + "."
  1172  }
  1173  
  1174  func (p *Package) emitMetaFile(outpath string) {
  1175  	// Open output file.
  1176  	of, err := os.OpenFile(outpath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
  1177  	if err != nil {
  1178  		log.Fatalf("opening covmeta %s: %v", outpath, err)
  1179  	}
  1180  
  1181  	if len(p.counterLengths) == 0 {
  1182  		// This corresponds to the case where we have no functions
  1183  		// in the package to instrument. Leave the file empty file if
  1184  		// this happens.
  1185  		if err = of.Close(); err != nil {
  1186  			log.Fatalf("closing meta-data file: %v", err)
  1187  		}
  1188  		return
  1189  	}
  1190  
  1191  	// Encode meta-data.
  1192  	var sws slicewriter.WriteSeeker
  1193  	digest, err := p.mdb.Emit(&sws)
  1194  	if err != nil {
  1195  		log.Fatalf("encoding meta-data: %v", err)
  1196  	}
  1197  	payload := sws.BytesWritten()
  1198  	blobs := [][]byte{payload}
  1199  
  1200  	// Write meta-data file directly.
  1201  	mfw := encodemeta.NewCoverageMetaFileWriter(outpath, of)
  1202  	err = mfw.Write(digest, blobs, cmode, cgran)
  1203  	if err != nil {
  1204  		log.Fatalf("writing meta-data file: %v", err)
  1205  	}
  1206  	if err = of.Close(); err != nil {
  1207  		log.Fatalf("closing meta-data file: %v", err)
  1208  	}
  1209  }
  1210
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