third_party/gofrontend/libgo/go/go/doc/example.go - llvm-project/llgo - Git at Google

 // Copyright 2011 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.

 // Extract example functions from file ASTs.

 package doc

 import (
 	"go/ast"
 	"go/token"
 	"path"
 	"regexp"
 	"sort"
 	"strconv"
 	"strings"
 	"unicode"
 	"unicode/utf8"
 )

 // An Example represents an example function found in a source files.
 type Example struct {
 	Name        string // name of the item being exemplified
 	Doc         string // example function doc string
 	Code        ast.Node
 	Play        *ast.File // a whole program version of the example
 	Comments    []*ast.CommentGroup
 	Output      string // expected output
 	EmptyOutput bool   // expect empty output
 	Order       int    // original source code order
 }

 // Examples returns the examples found in the files, sorted by Name field.
 // The Order fields record the order in which the examples were encountered.
 //
 // Playable Examples must be in a package whose name ends in "_test".
 // An Example is "playable" (the Play field is non-nil) in either of these
 // circumstances:
 //   - The example function is self-contained: the function references only
 //     identifiers from other packages (or predeclared identifiers, such as
 //     "int") and the test file does not include a dot import.
 //   - The entire test file is the example: the file contains exactly one
 //     example function, zero test or benchmark functions, and at least one
 //     top-level function, type, variable, or constant declaration other
 //     than the example function.
 func Examples(files ...*ast.File) []*Example {
 	var list []*Example
 	for _, file := range files {
 		hasTests := false // file contains tests or benchmarks
 		numDecl := 0      // number of non-import declarations in the file
 		var flist []*Example
 		for _, decl := range file.Decls {
 			if g, ok := decl.(*ast.GenDecl); ok && g.Tok != token.IMPORT {
 				numDecl++
 				continue
 			}
 			f, ok := decl.(*ast.FuncDecl)
 			if !ok {
 				continue
 			}
 			numDecl++
 			name := f.Name.Name
 			if isTest(name, "Test") || isTest(name, "Benchmark") {
 				hasTests = true
 				continue
 			}
 			if !isTest(name, "Example") {
 				continue
 			}
 			var doc string
 			if f.Doc != nil {
 				doc = f.Doc.Text()
 			}
 			output, hasOutput := exampleOutput(f.Body, file.Comments)
 			flist = append(flist, &Example{
 				Name:        name[len("Example"):],
 				Doc:         doc,
 				Code:        f.Body,
 				Play:        playExample(file, f.Body),
 				Comments:    file.Comments,
 				Output:      output,
 				EmptyOutput: output == "" && hasOutput,
 				Order:       len(flist),
 			})
 		}
 		if !hasTests && numDecl > 1 && len(flist) == 1 {
 			// If this file only has one example function, some
 			// other top-level declarations, and no tests or
 			// benchmarks, use the whole file as the example.
 			flist[0].Code = file
 			flist[0].Play = playExampleFile(file)
 		}
 		list = append(list, flist...)
 	}
 	sort.Sort(exampleByName(list))
 	return list
 }

 var outputPrefix = regexp.MustCompile(`(?i)^[[:space:]]*output:`)

 // Extracts the expected output and whether there was a valid output comment
 func exampleOutput(b *ast.BlockStmt, comments []*ast.CommentGroup) (output string, ok bool) {
 	if _, last := lastComment(b, comments); last != nil {
 		// test that it begins with the correct prefix
 		text := last.Text()
 		if loc := outputPrefix.FindStringIndex(text); loc != nil {
 			text = text[loc[1]:]
 			// Strip zero or more spaces followed by \n or a single space.
 			text = strings.TrimLeft(text, " ")
 			if len(text) > 0 && text[0] == '\n' {
 				text = text[1:]
 			}
 			return text, true
 		}
 	}
 	return "", false // no suitable comment found
 }

 // isTest tells whether name looks like a test, example, or benchmark.
 // It is a Test (say) if there is a character after Test that is not a
 // lower-case letter. (We don't want Testiness.)
 func isTest(name, prefix string) bool {
 	if !strings.HasPrefix(name, prefix) {
 		return false
 	}
 	if len(name) == len(prefix) { // "Test" is ok
 		return true
 	}
 	rune, _ := utf8.DecodeRuneInString(name[len(prefix):])
 	return !unicode.IsLower(rune)
 }

 type exampleByName []*Example

 func (s exampleByName) Len() int           { return len(s) }
 func (s exampleByName) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
 func (s exampleByName) Less(i, j int) bool { return s[i].Name < s[j].Name }

 // playExample synthesizes a new *ast.File based on the provided
 // file with the provided function body as the body of main.
 func playExample(file *ast.File, body *ast.BlockStmt) *ast.File {
 	if !strings.HasSuffix(file.Name.Name, "_test") {
 		// We don't support examples that are part of the
 		// greater package (yet).
 		return nil
 	}

 	// Find top-level declarations in the file.
 	topDecls := make(map[*ast.Object]bool)
 	for _, decl := range file.Decls {
 		switch d := decl.(type) {
 		case *ast.FuncDecl:
 			topDecls[d.Name.Obj] = true
 		case *ast.GenDecl:
 			for _, spec := range d.Specs {
 				switch s := spec.(type) {
 				case *ast.TypeSpec:
 					topDecls[s.Name.Obj] = true
 				case *ast.ValueSpec:
 					for _, id := range s.Names {
 						topDecls[id.Obj] = true
 					}
 				}
 			}
 		}
 	}

 	// Find unresolved identifiers and uses of top-level declarations.
 	unresolved := make(map[string]bool)
 	usesTopDecl := false
 	var inspectFunc func(ast.Node) bool
 	inspectFunc = func(n ast.Node) bool {
 		// For selector expressions, only inspect the left hand side.
 		// (For an expression like fmt.Println, only add "fmt" to the
 		// set of unresolved names, not "Println".)
 		if e, ok := n.(*ast.SelectorExpr); ok {
 			ast.Inspect(e.X, inspectFunc)
 			return false
 		}
 		// For key value expressions, only inspect the value
 		// as the key should be resolved by the type of the
 		// composite literal.
 		if e, ok := n.(*ast.KeyValueExpr); ok {
 			ast.Inspect(e.Value, inspectFunc)
 			return false
 		}
 		if id, ok := n.(*ast.Ident); ok {
 			if id.Obj == nil {
 				unresolved[id.Name] = true
 			} else if topDecls[id.Obj] {
 				usesTopDecl = true
 			}
 		}
 		return true
 	}
 	ast.Inspect(body, inspectFunc)
 	if usesTopDecl {
 		// We don't support examples that are not self-contained (yet).
 		return nil
 	}

 	// Remove predeclared identifiers from unresolved list.
 	for n := range unresolved {
 		if predeclaredTypes[n] || predeclaredConstants[n] || predeclaredFuncs[n] {
 			delete(unresolved, n)
 		}
 	}

 	// Use unresolved identifiers to determine the imports used by this
 	// example. The heuristic assumes package names match base import
 	// paths for imports w/o renames (should be good enough most of the time).
 	namedImports := make(map[string]string) // [name]path
 	var blankImports []ast.Spec             // _ imports
 	for _, s := range file.Imports {
 		p, err := strconv.Unquote(s.Path.Value)
 		if err != nil {
 			continue
 		}
 		n := path.Base(p)
 		if s.Name != nil {
 			n = s.Name.Name
 			switch n {
 			case "_":
 				blankImports = append(blankImports, s)
 				continue
 			case ".":
 				// We can't resolve dot imports (yet).
 				return nil
 			}
 		}
 		if unresolved[n] {
 			namedImports[n] = p
 			delete(unresolved, n)
 		}
 	}

 	// If there are other unresolved identifiers, give up because this
 	// synthesized file is not going to build.
 	if len(unresolved) > 0 {
 		return nil
 	}

 	// Include documentation belonging to blank imports.
 	var comments []*ast.CommentGroup
 	for _, s := range blankImports {
 		if c := s.(*ast.ImportSpec).Doc; c != nil {
 			comments = append(comments, c)
 		}
 	}

 	// Include comments that are inside the function body.
 	for _, c := range file.Comments {
 		if body.Pos() <= c.Pos() && c.End() <= body.End() {
 			comments = append(comments, c)
 		}
 	}

 	// Strip "Output:" comment and adjust body end position.
 	body, comments = stripOutputComment(body, comments)

 	// Synthesize import declaration.
 	importDecl := &ast.GenDecl{
 		Tok:    token.IMPORT,
 		Lparen: 1, // Need non-zero Lparen and Rparen so that printer
 		Rparen: 1, // treats this as a factored import.
 	}
 	for n, p := range namedImports {
 		s := &ast.ImportSpec{Path: &ast.BasicLit{Value: strconv.Quote(p)}}
 		if path.Base(p) != n {
 			s.Name = ast.NewIdent(n)
 		}
 		importDecl.Specs = append(importDecl.Specs, s)
 	}
 	importDecl.Specs = append(importDecl.Specs, blankImports...)

 	// Synthesize main function.
 	funcDecl := &ast.FuncDecl{
 		Name: ast.NewIdent("main"),
 		Type: &ast.FuncType{Params: &ast.FieldList{}}, // FuncType.Params must be non-nil
 		Body: body,
 	}

 	// Synthesize file.
 	return &ast.File{
 		Name:     ast.NewIdent("main"),
 		Decls:    []ast.Decl{importDecl, funcDecl},
 		Comments: comments,
 	}
 }

 // playExampleFile takes a whole file example and synthesizes a new *ast.File
 // such that the example is function main in package main.
 func playExampleFile(file *ast.File) *ast.File {
 	// Strip copyright comment if present.
 	comments := file.Comments
 	if len(comments) > 0 && strings.HasPrefix(comments[0].Text(), "Copyright") {
 		comments = comments[1:]
 	}

 	// Copy declaration slice, rewriting the ExampleX function to main.
 	var decls []ast.Decl
 	for _, d := range file.Decls {
 		if f, ok := d.(*ast.FuncDecl); ok && isTest(f.Name.Name, "Example") {
 			// Copy the FuncDecl, as it may be used elsewhere.
 			newF := *f
 			newF.Name = ast.NewIdent("main")
 			newF.Body, comments = stripOutputComment(f.Body, comments)
 			d = &newF
 		}
 		decls = append(decls, d)
 	}

 	// Copy the File, as it may be used elsewhere.
 	f := *file
 	f.Name = ast.NewIdent("main")
 	f.Decls = decls
 	f.Comments = comments
 	return &f
 }

 // stripOutputComment finds and removes an "Output:" comment from body
 // and comments, and adjusts the body block's end position.
 func stripOutputComment(body *ast.BlockStmt, comments []*ast.CommentGroup) (*ast.BlockStmt, []*ast.CommentGroup) {
 	// Do nothing if no "Output:" comment found.
 	i, last := lastComment(body, comments)
 	if last == nil || !outputPrefix.MatchString(last.Text()) {
 		return body, comments
 	}

 	// Copy body and comments, as the originals may be used elsewhere.
 	newBody := &ast.BlockStmt{
 		Lbrace: body.Lbrace,
 		List:   body.List,
 		Rbrace: last.Pos(),
 	}
 	newComments := make([]*ast.CommentGroup, len(comments)-1)
 	copy(newComments, comments[:i])
 	copy(newComments[i:], comments[i+1:])
 	return newBody, newComments
 }

 // lastComment returns the last comment inside the provided block.
 func lastComment(b *ast.BlockStmt, c []*ast.CommentGroup) (i int, last *ast.CommentGroup) {
 	pos, end := b.Pos(), b.End()
 	for j, cg := range c {
 		if cg.Pos() < pos {
 			continue
 		}
 		if cg.End() > end {
 			break
 		}
 		i, last = j, cg
 	}
 	return
 }
	// Copyright 2011 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.

	// Extract example functions from file ASTs.

	package doc

	import (
	"go/ast"
	"go/token"
	"path"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"unicode"
	"unicode/utf8"
	)

	// An Example represents an example function found in a source files.
	type Example struct {
	Name string // name of the item being exemplified
	Doc string // example function doc string
	Code ast.Node
	Play *ast.File // a whole program version of the example
	Comments []*ast.CommentGroup
	Output string // expected output
	EmptyOutput bool // expect empty output
	Order int // original source code order
	}

	// Examples returns the examples found in the files, sorted by Name field.
	// The Order fields record the order in which the examples were encountered.
	//
	// Playable Examples must be in a package whose name ends in "_test".
	// An Example is "playable" (the Play field is non-nil) in either of these
	// circumstances:
	// - The example function is self-contained: the function references only
	// identifiers from other packages (or predeclared identifiers, such as
	// "int") and the test file does not include a dot import.
	// - The entire test file is the example: the file contains exactly one
	// example function, zero test or benchmark functions, and at least one
	// top-level function, type, variable, or constant declaration other
	// than the example function.
	func Examples(files ...ast.File) []Example {
	var list []*Example
	for _, file := range files {
	hasTests := false // file contains tests or benchmarks
	numDecl := 0 // number of non-import declarations in the file
	var flist []*Example
	for _, decl := range file.Decls {
	if g, ok := decl.(*ast.GenDecl); ok && g.Tok != token.IMPORT {
	numDecl++
	continue
	}
	f, ok := decl.(*ast.FuncDecl)
	if !ok {
	continue
	}
	numDecl++
	name := f.Name.Name
	if isTest(name, "Test") \|\| isTest(name, "Benchmark") {
	hasTests = true
	continue
	}
	if !isTest(name, "Example") {
	continue
	}
	var doc string
	if f.Doc != nil {
	doc = f.Doc.Text()
	}
	output, hasOutput := exampleOutput(f.Body, file.Comments)
	flist = append(flist, &Example{
	Name: name[len("Example"):],
	Doc: doc,
	Code: f.Body,
	Play: playExample(file, f.Body),
	Comments: file.Comments,
	Output: output,
	EmptyOutput: output == "" && hasOutput,
	Order: len(flist),
	})
	}
	if !hasTests && numDecl > 1 && len(flist) == 1 {
	// If this file only has one example function, some
	// other top-level declarations, and no tests or
	// benchmarks, use the whole file as the example.
	flist[0].Code = file
	flist[0].Play = playExampleFile(file)
	}
	list = append(list, flist...)
	}
	sort.Sort(exampleByName(list))
	return list
	}

	var outputPrefix = regexp.MustCompile(`(?i)^[[:space:]]*output:`)

	// Extracts the expected output and whether there was a valid output comment
	func exampleOutput(b ast.BlockStmt, comments []ast.CommentGroup) (output string, ok bool) {
	if _, last := lastComment(b, comments); last != nil {
	// test that it begins with the correct prefix
	text := last.Text()
	if loc := outputPrefix.FindStringIndex(text); loc != nil {
	text = text[loc[1]:]
	// Strip zero or more spaces followed by \n or a single space.
	text = strings.TrimLeft(text, " ")
	if len(text) > 0 && text[0] == '\n' {
	text = text[1:]
	}
	return text, true
	}
	}
	return "", false // no suitable comment found
	}

	// isTest tells whether name looks like a test, example, or benchmark.
	// It is a Test (say) if there is a character after Test that is not a
	// lower-case letter. (We don't want Testiness.)
	func isTest(name, prefix string) bool {
	if !strings.HasPrefix(name, prefix) {
	return false
	}
	if len(name) == len(prefix) { // "Test" is ok
	return true
	}
	rune, _ := utf8.DecodeRuneInString(name[len(prefix):])
	return !unicode.IsLower(rune)
	}

	type exampleByName []*Example

	func (s exampleByName) Len() int { return len(s) }
	func (s exampleByName) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
	func (s exampleByName) Less(i, j int) bool { return s[i].Name < s[j].Name }

	// playExample synthesizes a new *ast.File based on the provided
	// file with the provided function body as the body of main.
	func playExample(file ast.File, body ast.BlockStmt) *ast.File {
	if !strings.HasSuffix(file.Name.Name, "_test") {
	// We don't support examples that are part of the
	// greater package (yet).
	return nil
	}

	// Find top-level declarations in the file.
	topDecls := make(map[*ast.Object]bool)
	for _, decl := range file.Decls {
	switch d := decl.(type) {
	case *ast.FuncDecl:
	topDecls[d.Name.Obj] = true
	case *ast.GenDecl:
	for _, spec := range d.Specs {
	switch s := spec.(type) {
	case *ast.TypeSpec:
	topDecls[s.Name.Obj] = true
	case *ast.ValueSpec:
	for _, id := range s.Names {
	topDecls[id.Obj] = true
	}
	}
	}
	}
	}

	// Find unresolved identifiers and uses of top-level declarations.
	unresolved := make(map[string]bool)
	usesTopDecl := false
	var inspectFunc func(ast.Node) bool
	inspectFunc = func(n ast.Node) bool {
	// For selector expressions, only inspect the left hand side.
	// (For an expression like fmt.Println, only add "fmt" to the
	// set of unresolved names, not "Println".)
	if e, ok := n.(*ast.SelectorExpr); ok {
	ast.Inspect(e.X, inspectFunc)
	return false
	}
	// For key value expressions, only inspect the value
	// as the key should be resolved by the type of the
	// composite literal.
	if e, ok := n.(*ast.KeyValueExpr); ok {
	ast.Inspect(e.Value, inspectFunc)
	return false
	}
	if id, ok := n.(*ast.Ident); ok {
	if id.Obj == nil {
	unresolved[id.Name] = true
	} else if topDecls[id.Obj] {
	usesTopDecl = true
	}
	}
	return true
	}
	ast.Inspect(body, inspectFunc)
	if usesTopDecl {
	// We don't support examples that are not self-contained (yet).
	return nil
	}

	// Remove predeclared identifiers from unresolved list.
	for n := range unresolved {
	if predeclaredTypes[n] \|\| predeclaredConstants[n] \|\| predeclaredFuncs[n] {
	delete(unresolved, n)
	}
	}

	// Use unresolved identifiers to determine the imports used by this
	// example. The heuristic assumes package names match base import
	// paths for imports w/o renames (should be good enough most of the time).
	namedImports := make(map[string]string) // [name]path
	var blankImports []ast.Spec // _ imports
	for _, s := range file.Imports {
	p, err := strconv.Unquote(s.Path.Value)
	if err != nil {
	continue
	}
	n := path.Base(p)
	if s.Name != nil {
	n = s.Name.Name
	switch n {
	case "_":
	blankImports = append(blankImports, s)
	continue
	case ".":
	// We can't resolve dot imports (yet).
	return nil
	}
	}
	if unresolved[n] {
	namedImports[n] = p
	delete(unresolved, n)
	}
	}

	// If there are other unresolved identifiers, give up because this
	// synthesized file is not going to build.
	if len(unresolved) > 0 {
	return nil
	}

	// Include documentation belonging to blank imports.
	var comments []*ast.CommentGroup
	for _, s := range blankImports {
	if c := s.(*ast.ImportSpec).Doc; c != nil {
	comments = append(comments, c)
	}
	}

	// Include comments that are inside the function body.
	for _, c := range file.Comments {
	if body.Pos() <= c.Pos() && c.End() <= body.End() {
	comments = append(comments, c)
	}
	}

	// Strip "Output:" comment and adjust body end position.
	body, comments = stripOutputComment(body, comments)

	// Synthesize import declaration.
	importDecl := &ast.GenDecl{
	Tok: token.IMPORT,
	Lparen: 1, // Need non-zero Lparen and Rparen so that printer
	Rparen: 1, // treats this as a factored import.
	}
	for n, p := range namedImports {
	s := &ast.ImportSpec{Path: &ast.BasicLit{Value: strconv.Quote(p)}}
	if path.Base(p) != n {
	s.Name = ast.NewIdent(n)
	}
	importDecl.Specs = append(importDecl.Specs, s)
	}
	importDecl.Specs = append(importDecl.Specs, blankImports...)

	// Synthesize main function.
	funcDecl := &ast.FuncDecl{
	Name: ast.NewIdent("main"),
	Type: &ast.FuncType{Params: &ast.FieldList{}}, // FuncType.Params must be non-nil
	Body: body,
	}

	// Synthesize file.
	return &ast.File{
	Name: ast.NewIdent("main"),
	Decls: []ast.Decl{importDecl, funcDecl},
	Comments: comments,
	}
	}

	// playExampleFile takes a whole file example and synthesizes a new *ast.File
	// such that the example is function main in package main.
	func playExampleFile(file ast.File) ast.File {
	// Strip copyright comment if present.
	comments := file.Comments
	if len(comments) > 0 && strings.HasPrefix(comments[0].Text(), "Copyright") {
	comments = comments[1:]
	}

	// Copy declaration slice, rewriting the ExampleX function to main.
	var decls []ast.Decl
	for _, d := range file.Decls {
	if f, ok := d.(*ast.FuncDecl); ok && isTest(f.Name.Name, "Example") {
	// Copy the FuncDecl, as it may be used elsewhere.
	newF := *f
	newF.Name = ast.NewIdent("main")
	newF.Body, comments = stripOutputComment(f.Body, comments)
	d = &newF
	}
	decls = append(decls, d)
	}

	// Copy the File, as it may be used elsewhere.
	f := *file
	f.Name = ast.NewIdent("main")
	f.Decls = decls
	f.Comments = comments
	return &f
	}

	// stripOutputComment finds and removes an "Output:" comment from body
	// and comments, and adjusts the body block's end position.
	func stripOutputComment(body ast.BlockStmt, comments []ast.CommentGroup) (ast.BlockStmt, []ast.CommentGroup) {
	// Do nothing if no "Output:" comment found.
	i, last := lastComment(body, comments)
	if last == nil \|\| !outputPrefix.MatchString(last.Text()) {
	return body, comments
	}

	// Copy body and comments, as the originals may be used elsewhere.
	newBody := &ast.BlockStmt{
	Lbrace: body.Lbrace,
	List: body.List,
	Rbrace: last.Pos(),
	}
	newComments := make([]*ast.CommentGroup, len(comments)-1)
	copy(newComments, comments[:i])
	copy(newComments[i:], comments[i+1:])
	return newBody, newComments
	}

	// lastComment returns the last comment inside the provided block.
	func lastComment(b ast.BlockStmt, c []ast.CommentGroup) (i int, last *ast.CommentGroup) {
	pos, end := b.Pos(), b.End()
	for j, cg := range c {
	if cg.Pos() < pos {
	continue
	}
	if cg.End() > end {
	break
	}
	i, last = j, cg
	}
	return
	}