go cover 源码
golang cover 代码
文件路径：/src/cmd/cover/cover.go
// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import (
"bytes"
"flag"
"fmt"
"go/ast"
"go/parser"
"go/token"
"io"
"log"
"os"
"sort"
"cmd/internal/edit"
"cmd/internal/objabi"
)
const usageMessage = "" +
`Usage of 'go tool cover':
Given a coverage profile produced by 'go test':
go test -coverprofile=c.out
Open a web browser displaying annotated source code:
go tool cover -html=c.out
Write out an HTML file instead of launching a web browser:
go tool cover -html=c.out -o coverage.html
Display coverage percentages to stdout for each function:
go tool cover -func=c.out
Finally, to generate modified source code with coverage annotations
(what go test -cover does):
go tool cover -mode=set -var=CoverageVariableName program.go
`
func usage() {
fmt.Fprint(os.Stderr, usageMessage)
fmt.Fprintln(os.Stderr, "\nFlags:")
flag.PrintDefaults()
fmt.Fprintln(os.Stderr, "\n Only one of -html, -func, or -mode may be set.")
os.Exit(2)
}
var (
mode = flag.String("mode", "", "coverage mode: set, count, atomic")
varVar = flag.String("var", "GoCover", "name of coverage variable to generate")
output = flag.String("o", "", "file for output; default: stdout")
htmlOut = flag.String("html", "", "generate HTML representation of coverage profile")
funcOut = flag.String("func", "", "output coverage profile information for each function")
)
var profile string // The profile to read; the value of -html or -func
var counterStmt func(*File, string) string
const (
atomicPackagePath = "sync/atomic"
atomicPackageName = "_cover_atomic_"
)
func main() {
objabi.AddVersionFlag()
flag.Usage = usage
flag.Parse()
// Usage information when no arguments.
if flag.NFlag() == 0 && flag.NArg() == 0 {
flag.Usage()
}
err := parseFlags()
if err != nil {
fmt.Fprintln(os.Stderr, err)
fmt.Fprintln(os.Stderr, `For usage information, run "go tool cover -help"`)
os.Exit(2)
}
// Generate coverage-annotated source.
if *mode != "" {
annotate(flag.Arg(0))
return
}
// Output HTML or function coverage information.
if *htmlOut != "" {
err = htmlOutput(profile, *output)
} else {
err = funcOutput(profile, *output)
}
if err != nil {
fmt.Fprintf(os.Stderr, "cover: %v\n", err)
os.Exit(2)
}
}
// parseFlags sets the profile and counterStmt globals and performs validations.
func parseFlags() error {
profile = *htmlOut
if *funcOut != "" {
if profile != "" {
return fmt.Errorf("too many options")
}
profile = *funcOut
}
// Must either display a profile or rewrite Go source.
if (profile == "") == (*mode == "") {
return fmt.Errorf("too many options")
}
if *varVar != "" && !token.IsIdentifier(*varVar) {
return fmt.Errorf("-var: %q is not a valid identifier", *varVar)
}
if *mode != "" {
switch *mode {
case "set":
counterStmt = setCounterStmt
case "count":
counterStmt = incCounterStmt
case "atomic":
counterStmt = atomicCounterStmt
default:
return fmt.Errorf("unknown -mode %v", *mode)
}
if flag.NArg() == 0 {
return fmt.Errorf("missing source file")
} else if flag.NArg() == 1 {
return nil
}
} else if flag.NArg() == 0 {
return nil
}
return fmt.Errorf("too many arguments")
}
// Block represents the information about a basic block to be recorded in the analysis.
// Note: Our definition of basic block is based on control structures; we don't break
// apart && and ||. We could but it doesn't seem important enough to bother.
type Block struct {
startByte token.Pos
endByte token.Pos
numStmt int
}
// File is a wrapper for the state of a file used in the parser.
// The basic parse tree walker is a method of this type.
type File struct {
fset *token.FileSet
name string // Name of file.
astFile *ast.File
blocks []Block
content []byte
edit *edit.Buffer
}
// findText finds text in the original source, starting at pos.
// It correctly skips over comments and assumes it need not
// handle quoted strings.
// It returns a byte offset within f.src.
func (f *File) findText(pos token.Pos, text string) int {
b := []byte(text)
start := f.offset(pos)
i := start
s := f.content
for i < len(s) {
if bytes.HasPrefix(s[i:], b) {
return i
}
if i+2 <= len(s) && s[i] == '/' && s[i+1] == '/' {
for i < len(s) && s[i] != '\n' {
i++
}
continue
}
if i+2 <= len(s) && s[i] == '/' && s[i+1] == '*' {
for i += 2; ; i++ {
if i+2 > len(s) {
return 0
}
if s[i] == '*' && s[i+1] == '/' {
i += 2
break
}
}
continue
}
i++
}
return -1
}
// Visit implements the ast.Visitor interface.
func (f *File) Visit(node ast.Node) ast.Visitor {
switch n := node.(type) {
case *ast.BlockStmt:
// If it's a switch or select, the body is a list of case clauses; don't tag the block itself.
if len(n.List) > 0 {
switch n.List[0].(type) {
case *ast.CaseClause: // switch
for _, n := range n.List {
clause := n.(*ast.CaseClause)
f.addCounters(clause.Colon+1, clause.Colon+1, clause.End(), clause.Body, false)
}
return f
case *ast.CommClause: // select
for _, n := range n.List {
clause := n.(*ast.CommClause)
f.addCounters(clause.Colon+1, clause.Colon+1, clause.End(), clause.Body, false)
}
return f
}
}
f.addCounters(n.Lbrace, n.Lbrace+1, n.Rbrace+1, n.List, true) // +1 to step past closing brace.
case *ast.IfStmt:
if n.Init != nil {
ast.Walk(f, n.Init)
}
ast.Walk(f, n.Cond)
ast.Walk(f, n.Body)
if n.Else == nil {
return nil
}
// The elses are special, because if we have
// if x {
// } else if y {
// }
// we want to cover the "if y". To do this, we need a place to drop the counter,
// so we add a hidden block:
// if x {
// } else {
// if y {
// }
// }
elseOffset := f.findText(n.Body.End(), "else")
if elseOffset < 0 {
panic("lost else")
}
f.edit.Insert(elseOffset+4, "{")
f.edit.Insert(f.offset(n.Else.End()), "}")
// We just created a block, now walk it.
// Adjust the position of the new block to start after
// the "else". That will cause it to follow the "{"
// we inserted above.
pos := f.fset.File(n.Body.End()).Pos(elseOffset + 4)
switch stmt := n.Else.(type) {
case *ast.IfStmt:
block := &ast.BlockStmt{
Lbrace: pos,
List: []ast.Stmt{stmt},
Rbrace: stmt.End(),
}
n.Else = block
case *ast.BlockStmt:
stmt.Lbrace = pos
default:
panic("unexpected node type in if")
}
ast.Walk(f, n.Else)
return nil
case *ast.SelectStmt:
// Don't annotate an empty select - creates a syntax error.
if n.Body == nil || len(n.Body.List) == 0 {
return nil
}
case *ast.SwitchStmt:
// Don't annotate an empty switch - creates a syntax error.
if n.Body == nil || len(n.Body.List) == 0 {
if n.Init != nil {
ast.Walk(f, n.Init)
}
if n.Tag != nil {
ast.Walk(f, n.Tag)
}
return nil
}
case *ast.TypeSwitchStmt:
// Don't annotate an empty type switch - creates a syntax error.
if n.Body == nil || len(n.Body.List) == 0 {
if n.Init != nil {
ast.Walk(f, n.Init)
}
ast.Walk(f, n.Assign)
return nil
}
case *ast.FuncDecl:
// Don't annotate functions with blank names - they cannot be executed.
if n.Name.Name == "_" {
return nil
}
}
return f
}
func annotate(name string) {
fset := token.NewFileSet()
content, err := os.ReadFile(name)
if err != nil {
log.Fatalf("cover: %s: %s", name, err)
}
parsedFile, err := parser.ParseFile(fset, name, content, parser.ParseComments)
if err != nil {
log.Fatalf("cover: %s: %s", name, err)
}
file := &File{
fset: fset,
name: name,
content: content,
edit: edit.NewBuffer(content),
astFile: parsedFile,
}
if *mode == "atomic" {
// Add import of sync/atomic immediately after package clause.
// We do this even if there is an existing import, because the
// existing import may be shadowed at any given place we want
// to refer to it, and our name (_cover_atomic_) is less likely to
// be shadowed.
file.edit.Insert(file.offset(file.astFile.Name.End()),
fmt.Sprintf("; import %s %q", atomicPackageName, atomicPackagePath))
}
ast.Walk(file, file.astFile)
newContent := file.edit.Bytes()
fd := os.Stdout
if *output != "" {
var err error
fd, err = os.Create(*output)
if err != nil {
log.Fatalf("cover: %s", err)
}
}
fmt.Fprintf(fd, "//line %s:1\n", name)
fd.Write(newContent)
// After printing the source tree, add some declarations for the counters etc.
// We could do this by adding to the tree, but it's easier just to print the text.
file.addVariables(fd)
}
// setCounterStmt returns the expression: __count[23] = 1.
func setCounterStmt(f *File, counter string) string {
return fmt.Sprintf("%s = 1", counter)
}
// incCounterStmt returns the expression: __count[23]++.
func incCounterStmt(f *File, counter string) string {
return fmt.Sprintf("%s++", counter)
}
// atomicCounterStmt returns the expression: atomic.AddUint32(&__count[23], 1)
func atomicCounterStmt(f *File, counter string) string {
return fmt.Sprintf("%s.AddUint32(&%s, 1)", atomicPackageName, counter)
}
// newCounter creates a new counter expression of the appropriate form.
func (f *File) newCounter(start, end token.Pos, numStmt int) string {
stmt := counterStmt(f, fmt.Sprintf("%s.Count[%d]", *varVar, len(f.blocks)))
f.blocks = append(f.blocks, Block{start, end, numStmt})
return stmt
}
// addCounters takes a list of statements and adds counters to the beginning of
// each basic block at the top level of that list. For instance, given
//
// S1
// if cond {
// S2
// }
// S3
//
// counters will be added before S1 and before S3. The block containing S2
// will be visited in a separate call.
// TODO: Nested simple blocks get unnecessary (but correct) counters
func (f *File) addCounters(pos, insertPos, blockEnd token.Pos, list []ast.Stmt, extendToClosingBrace bool) {
// Special case: make sure we add a counter to an empty block. Can't do this below
// or we will add a counter to an empty statement list after, say, a return statement.
if len(list) == 0 {
f.edit.Insert(f.offset(insertPos), f.newCounter(insertPos, blockEnd, 0)+";")
return
}
// Make a copy of the list, as we may mutate it and should leave the
// existing list intact.
list = append([]ast.Stmt(nil), list...)
// We have a block (statement list), but it may have several basic blocks due to the
// appearance of statements that affect the flow of control.
for {
// Find first statement that affects flow of control (break, continue, if, etc.).
// It will be the last statement of this basic block.
var last int
end := blockEnd
for last = 0; last < len(list); last++ {
stmt := list[last]
end = f.statementBoundary(stmt)
if f.endsBasicSourceBlock(stmt) {
// If it is a labeled statement, we need to place a counter between
// the label and its statement because it may be the target of a goto
// and thus start a basic block. That is, given
// foo: stmt
// we need to create
// foo: ; stmt
// and mark the label as a block-terminating statement.
// The result will then be
// foo: COUNTER[n]++; stmt
// However, we can't do this if the labeled statement is already
// a control statement, such as a labeled for.
if label, isLabel := stmt.(*ast.LabeledStmt); isLabel && !f.isControl(label.Stmt) {
newLabel := *label
newLabel.Stmt = &ast.EmptyStmt{
Semicolon: label.Stmt.Pos(),
Implicit: true,
}
end = label.Pos() // Previous block ends before the label.
list[last] = &newLabel
// Open a gap and drop in the old statement, now without a label.
list = append(list, nil)
copy(list[last+1:], list[last:])
list[last+1] = label.Stmt
}
last++
extendToClosingBrace = false // Block is broken up now.
break
}
}
if extendToClosingBrace {
end = blockEnd
}
if pos != end { // Can have no source to cover if e.g. blocks abut.
f.edit.Insert(f.offset(insertPos), f.newCounter(pos, end, last)+";")
}
list = list[last:]
if len(list) == 0 {
break
}
pos = list[0].Pos()
insertPos = pos
}
}
// hasFuncLiteral reports the existence and position of the first func literal
// in the node, if any. If a func literal appears, it usually marks the termination
// of a basic block because the function body is itself a block.
// Therefore we draw a line at the start of the body of the first function literal we find.
// TODO: what if there's more than one? Probably doesn't matter much.
func hasFuncLiteral(n ast.Node) (bool, token.Pos) {
if n == nil {
return false, 0
}
var literal funcLitFinder
ast.Walk(&literal, n)
return literal.found(), token.Pos(literal)
}
// statementBoundary finds the location in s that terminates the current basic
// block in the source.
func (f *File) statementBoundary(s ast.Stmt) token.Pos {
// Control flow statements are easy.
switch s := s.(type) {
case *ast.BlockStmt:
// Treat blocks like basic blocks to avoid overlapping counters.
return s.Lbrace
case *ast.IfStmt:
found, pos := hasFuncLiteral(s.Init)
if found {
return pos
}
found, pos = hasFuncLiteral(s.Cond)
if found {
return pos
}
return s.Body.Lbrace
case *ast.ForStmt:
found, pos := hasFuncLiteral(s.Init)
if found {
return pos
}
found, pos = hasFuncLiteral(s.Cond)
if found {
return pos
}
found, pos = hasFuncLiteral(s.Post)
if found {
return pos
}
return s.Body.Lbrace
case *ast.LabeledStmt:
return f.statementBoundary(s.Stmt)
case *ast.RangeStmt:
found, pos := hasFuncLiteral(s.X)
if found {
return pos
}
return s.Body.Lbrace
case *ast.SwitchStmt:
found, pos := hasFuncLiteral(s.Init)
if found {
return pos
}
found, pos = hasFuncLiteral(s.Tag)
if found {
return pos
}
return s.Body.Lbrace
case *ast.SelectStmt:
return s.Body.Lbrace
case *ast.TypeSwitchStmt:
found, pos := hasFuncLiteral(s.Init)
if found {
return pos
}
return s.Body.Lbrace
}
// If not a control flow statement, it is a declaration, expression, call, etc. and it may have a function literal.
// If it does, that's tricky because we want to exclude the body of the function from this block.
// Draw a line at the start of the body of the first function literal we find.
// TODO: what if there's more than one? Probably doesn't matter much.
found, pos := hasFuncLiteral(s)
if found {
return pos
}
return s.End()
}
// endsBasicSourceBlock reports whether s changes the flow of control: break, if, etc.,
// or if it's just problematic, for instance contains a function literal, which will complicate
// accounting due to the block-within-an expression.
func (f *File) endsBasicSourceBlock(s ast.Stmt) bool {
switch s := s.(type) {
case *ast.BlockStmt:
// Treat blocks like basic blocks to avoid overlapping counters.
return true
case *ast.BranchStmt:
return true
case *ast.ForStmt:
return true
case *ast.IfStmt:
return true
case *ast.LabeledStmt:
return true // A goto may branch here, starting a new basic block.
case *ast.RangeStmt:
return true
case *ast.SwitchStmt:
return true
case *ast.SelectStmt:
return true
case *ast.TypeSwitchStmt:
return true
case *ast.ExprStmt:
// Calls to panic change the flow.
// We really should verify that "panic" is the predefined function,
// but without type checking we can't and the likelihood of it being
// an actual problem is vanishingly small.
if call, ok := s.X.(*ast.CallExpr); ok {
if ident, ok := call.Fun.(*ast.Ident); ok && ident.Name == "panic" && len(call.Args) == 1 {
return true
}
}
}
found, _ := hasFuncLiteral(s)
return found
}
// isControl reports whether s is a control statement that, if labeled, cannot be
// separated from its label.
func (f *File) isControl(s ast.Stmt) bool {
switch s.(type) {
case *ast.ForStmt, *ast.RangeStmt, *ast.SwitchStmt, *ast.SelectStmt, *ast.TypeSwitchStmt:
return true
}
return false
}
// funcLitFinder implements the ast.Visitor pattern to find the location of any
// function literal in a subtree.
type funcLitFinder token.Pos
func (f *funcLitFinder) Visit(node ast.Node) (w ast.Visitor) {
if f.found() {
return nil // Prune search.
}
switch n := node.(type) {
case *ast.FuncLit:
*f = funcLitFinder(n.Body.Lbrace)
return nil // Prune search.
}
return f
}
func (f *funcLitFinder) found() bool {
return token.Pos(*f) != token.NoPos
}
// Sort interface for []block1; used for self-check in addVariables.
type block1 struct {
Block
index int
}
type blockSlice []block1
func (b blockSlice) Len() int { return len(b) }
func (b blockSlice) Less(i, j int) bool { return b[i].startByte < b[j].startByte }
func (b blockSlice) Swap(i, j int) { b[i], b[j] = b[j], b[i] }
// offset translates a token position into a 0-indexed byte offset.
func (f *File) offset(pos token.Pos) int {
return f.fset.Position(pos).Offset
}
// addVariables adds to the end of the file the declarations to set up the counter and position variables.
func (f *File) addVariables(w io.Writer) {
// Self-check: Verify that the instrumented basic blocks are disjoint.
t := make([]block1, len(f.blocks))
for i := range f.blocks {
t[i].Block = f.blocks[i]
t[i].index = i
}
sort.Sort(blockSlice(t))
for i := 1; i < len(t); i++ {
if t[i-1].endByte > t[i].startByte {
fmt.Fprintf(os.Stderr, "cover: internal error: block %d overlaps block %d\n", t[i-1].index, t[i].index)
// Note: error message is in byte positions, not token positions.
fmt.Fprintf(os.Stderr, "\t%s:#%d,#%d %s:#%d,#%d\n",
f.name, f.offset(t[i-1].startByte), f.offset(t[i-1].endByte),
f.name, f.offset(t[i].startByte), f.offset(t[i].endByte))
}
}
// Declare the coverage struct as a package-level variable.
fmt.Fprintf(w, "\nvar %s = struct {\n", *varVar)
fmt.Fprintf(w, "\tCount [%d]uint32\n", len(f.blocks))
fmt.Fprintf(w, "\tPos [3 * %d]uint32\n", len(f.blocks))
fmt.Fprintf(w, "\tNumStmt [%d]uint16\n", len(f.blocks))
fmt.Fprintf(w, "} {\n")
// Initialize the position array field.
fmt.Fprintf(w, "\tPos: [3 * %d]uint32{\n", len(f.blocks))
// A nice long list of positions. Each position is encoded as follows to reduce size:
// - 32-bit starting line number
// - 32-bit ending line number
// - (16 bit ending column number << 16) | (16-bit starting column number).
for i, block := range f.blocks {
start := f.fset.Position(block.startByte)
end := f.fset.Position(block.endByte)
start, end = dedup(start, end)
fmt.Fprintf(w, "\t\t%d, %d, %#x, // [%d]\n", start.Line, end.Line, (end.Column&0xFFFF)<<16|(start.Column&0xFFFF), i)
}
// Close the position array.
fmt.Fprintf(w, "\t},\n")
// Initialize the position array field.
fmt.Fprintf(w, "\tNumStmt: [%d]uint16{\n", len(f.blocks))
// A nice long list of statements-per-block, so we can give a conventional
// valuation of "percent covered". To save space, it's a 16-bit number, so we
// clamp it if it overflows - won't matter in practice.
for i, block := range f.blocks {
n := block.numStmt
if n > 1<<16-1 {
n = 1<<16 - 1
}
fmt.Fprintf(w, "\t\t%d, // %d\n", n, i)
}
// Close the statements-per-block array.
fmt.Fprintf(w, "\t},\n")
// Close the struct initialization.
fmt.Fprintf(w, "}\n")
// Emit a reference to the atomic package to avoid
// import and not used error when there's no code in a file.
if *mode == "atomic" {
fmt.Fprintf(w, "var _ = %s.LoadUint32\n", atomicPackageName)
}
}
// It is possible for positions to repeat when there is a line
// directive that does not specify column information and the input
// has not been passed through gofmt.
// See issues #27530 and #30746.
// Tests are TestHtmlUnformatted and TestLineDup.
// We use a map to avoid duplicates.
// pos2 is a pair of token.Position values, used as a map key type.
type pos2 struct {
p1, p2 token.Position
}
// seenPos2 tracks whether we have seen a token.Position pair.
var seenPos2 = make(map[pos2]bool)
// dedup takes a token.Position pair and returns a pair that does not
// duplicate any existing pair. The returned pair will have the Offset
// fields cleared.
func dedup(p1, p2 token.Position) (r1, r2 token.Position) {
key := pos2{
p1: p1,
p2: p2,
}
// We want to ignore the Offset fields in the map,
// since cover uses only file/line/column.
key.p1.Offset = 0
key.p2.Offset = 0
for seenPos2[key] {
key.p2.Column++
}
seenPos2[key] = true
return key.p1, key.p2
}
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