relnote/links.go - build - Git at Google

 // Copyright 2024 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 relnote

 import (
 	"fmt"
 	"strings"
 	"unicode"
 	"unicode/utf8"

 	"golang.org/x/mod/module"
 	md "rsc.io/markdown"
 )

 // addSymbolLinks looks for text like [Buffer] and
 // [math.Max] and replaces them with links to standard library
 // symbols and packages.
 // It uses the given default package for links without a package.
 func addSymbolLinks(doc *md.Document, defaultPackage string) {
 	addSymbolLinksBlocks(doc.Blocks, defaultPackage)
 }

 func addSymbolLinksBlocks(bs []md.Block, defaultPackage string) {
 	for _, b := range bs {
 		addSymbolLinksBlock(b, defaultPackage)
 	}
 }

 func addSymbolLinksBlock(b md.Block, defaultPackage string) {
 	switch b := b.(type) {
 	case *md.Heading:
 		addSymbolLinksBlock(b.Text, defaultPackage)
 	case *md.Text:
 		b.Inline = addSymbolLinksInlines(b.Inline, defaultPackage)
 	case *md.List:
 		addSymbolLinksBlocks(b.Items, defaultPackage)
 	case *md.Item:
 		addSymbolLinksBlocks(b.Blocks, defaultPackage)
 	case *md.Paragraph:
 		addSymbolLinksBlock(b.Text, defaultPackage)
 	case *md.Quote:
 		addSymbolLinksBlocks(b.Blocks, defaultPackage)
 	// no links in these blocks
 	case *md.CodeBlock:
 	case *md.HTMLBlock:
 	case *md.Empty:
 	case *md.ThematicBreak:
 	default:
 		panic(fmt.Sprintf("unknown block type %T", b))
 	}
 }

 // addSymbolLinksInlines looks for symbol links in the slice of inline markdown
 // elements. It returns a new slice of inline elements with links added.
 func addSymbolLinksInlines(ins []md.Inline, defaultPackage string) []md.Inline {
 	ins = splitAtBrackets(ins)
 	var res []md.Inline
 	for i := 0; i < len(ins); i++ {
 		if txt := symbolLinkText(i, ins); txt != "" {
 			link, ok := symbolLink(txt, defaultPackage)
 			if ok {
 				res = append(res, link)
 				i += 2
 				continue
 			}
 		}

 		switch in := ins[i].(type) {
 		case *md.Strong:
 			res = append(res, addSymbolLinksInlines(in.Inner, defaultPackage)...)
 		case *md.Emph:
 			res = append(res, addSymbolLinksInlines(in.Inner, defaultPackage)...)
 		case *md.Del:
 			res = append(res, addSymbolLinksInlines(in.Inner, defaultPackage)...)
 		// Don't look for links in anything else.
 		default:
 			res = append(res, in)
 		}
 	}
 	return res
 }

 // splitAtBrackets rewrites ins so that every '[' and ']' is the only character
 // of its Plain.
 // For example, the element
 //
 //	[Plain("the [Buffer] is")]
 //
 // is rewritten to
 //
 //	[Plain("the "), Plain("["), Plain("Buffer"), Plain("]"), Plain(" is")]
 //
 // This transformation simplifies looking for symbol links.
 func splitAtBrackets(ins []md.Inline) []md.Inline {
 	var res []md.Inline
 	for _, in := range ins {
 		if p, ok := in.(*md.Plain); ok {
 			text := p.Text
 			for len(text) > 0 {
 				i := strings.IndexAny(text, "[]")
 				// If there are no brackets, the remaining text is a single
 				// Plain and we are done.
 				if i < 0 {
 					res = append(res, &md.Plain{Text: text})
 					break
 				}
 				// There is a bracket; make Plains for it and the text before it (if any).
 				if i > 0 {
 					res = append(res, &md.Plain{Text: text[:i]})
 				}
 				res = append(res, &md.Plain{Text: text[i : i+1]})
 				text = text[i+1:]
 			}
 		} else {
 			res = append(res, in)
 		}
 	}
 	return res
 }

 // symbolLinkText returns the text of a possible symbol link.
 // It is given a slice of Inline elements and an index into the slice.
 // If the index refers to a sequence of elements
 //
 //	[Plain("["), Plain_or_Code(text), Plain("]")]
 //
 // and the brackets are adjacent to the right kind of runes for a link, then
 // symbolLinkText returns the text of the middle element.
 // Otherwise it returns the empty string.
 func symbolLinkText(i int, ins []md.Inline) string {
 	// plainText returns the text of ins[j] if it is a Plain element, or "" otherwise.
 	plainText := func(j int) string {
 		if j < 0 || j >= len(ins) {
 			return ""
 		}
 		if p, ok := ins[j].(*md.Plain); ok {
 			return p.Text
 		}
 		return ""
 	}

 	// ins[i] must be a "[".
 	if plainText(i) != "[" {
 		return ""
 	}
 	// The open bracket must be preceeded by a link-adjacent rune (or by nothing).
 	if t := plainText(i - 1); t != "" {
 		r, _ := utf8.DecodeLastRuneInString(t)
 		if !isLinkAdjacentRune(r) {
 			return ""
 		}
 	}
 	// The element after the next must be a ']'.
 	if plainText(i+2) != "]" {
 		return ""
 	}
 	// The ']' must be followed by a link-adjacent rune (or by nothing).
 	if t := plainText(i + 3); t != "" {
 		r, _ := utf8.DecodeRuneInString(t)
 		if !isLinkAdjacentRune(r) {
 			return ""
 		}
 	}

 	// ins[i+1] must be a Plain or a Code.
 	// Its text is the symbol to link to.
 	if i+1 >= len(ins) {
 		return ""
 	}
 	switch in := ins[i+1].(type) {
 	case *md.Plain:
 		return in.Text
 	case *md.Code:
 		return in.Text
 	default:
 		return ""
 	}
 }

 // symbolLink converts s into a Link and returns it and true, or nil and false if
 // s is not a valid link or is surrounded by runes that disqualify it from being
 // converted to a link.
 //
 // The argument s is the text between '[' and ']'.
 func symbolLink(s, defaultPackage string) (md.Inline, bool) {
 	pkg, sym, ok := splitRef(s)
 	if !ok {
 		return nil, false
 	}
 	if pkg == "" {
 		if defaultPackage == "" {
 			return nil, false
 		}
 		pkg = defaultPackage
 	}
 	if sym != "" {
 		sym = "#" + sym
 	}
 	return &md.Link{
 		Inner: []md.Inline{&md.Code{Text: s}},
 		URL:   fmt.Sprintf("/pkg/%s%s", pkg, sym),
 	}, true
 }

 // isLinkAdjacentRune reports whether r can be adjacent to a symbol link.
 // The logic is the same as the go/doc/comment package.
 func isLinkAdjacentRune(r rune) bool {
 	return unicode.IsPunct(r) || r == ' ' || r == '\t' || r == '\n'
 }

 // splitRef splits s into a package and possibly a symbol.
 // Examples:
 //
 //	splitRef("math.Max") => ("math", "Max", true)
 //	splitRef("bytes.Buffer.String") => ("bytes", "Buffer.String", true)
 //	splitRef("math") => ("math", "", true)
 func splitRef(s string) (pkg, name string, ok bool) {
 	s = strings.TrimPrefix(s, "*")
 	pkg, name, ok = splitDocName(s)
 	var recv string
 	if ok {
 		pkg, recv, _ = splitDocName(pkg)
 	}
 	if pkg != "" {
 		if err := module.CheckImportPath(pkg); err != nil {
 			return "", "", false
 		}
 	}
 	if recv != "" {
 		name = recv + "." + name
 	}
 	return pkg, name, true
 }

 // The following functions were copied from go/doc/comment/parse.go.

 // If text is of the form before.Name, where Name is a capitalized Go identifier,
 // then splitDocName returns before, name, true.
 // Otherwise it returns text, "", false.
 func splitDocName(text string) (before, name string, foundDot bool) {
 	i := strings.LastIndex(text, ".")
 	name = text[i+1:]
 	if !isName(name) {
 		return text, "", false
 	}
 	if i >= 0 {
 		before = text[:i]
 	}
 	return before, name, true
 }

 // isName reports whether s is a capitalized Go identifier (like Name).
 func isName(s string) bool {
 	t, ok := ident(s)
 	if !ok || t != s {
 		return false
 	}
 	r, _ := utf8.DecodeRuneInString(s)
 	return unicode.IsUpper(r)
 }

 // ident checks whether s begins with a Go identifier.
 // If so, it returns the identifier, which is a prefix of s, and ok == true.
 // Otherwise it returns "", false.
 // The caller should skip over the first len(id) bytes of s
 // before further processing.
 func ident(s string) (id string, ok bool) {
 	// Scan [\pL_][\pL_0-9]*
 	n := 0
 	for n < len(s) {
 		if c := s[n]; c < utf8.RuneSelf {
 			if isIdentASCII(c) && (n > 0 || c < '0' || c > '9') {
 				n++
 				continue
 			}
 			break
 		}
 		r, nr := utf8.DecodeRuneInString(s[n:])
 		if unicode.IsLetter(r) {
 			n += nr
 			continue
 		}
 		break
 	}
 	return s[:n], n > 0
 }

 // isIdentASCII reports whether c is an ASCII identifier byte.
 func isIdentASCII(c byte) bool {
 	// mask is a 128-bit bitmap with 1s for allowed bytes,
 	// so that the byte c can be tested with a shift and an and.
 	// If c > 128, then 1<<c and 1<<(c-64) will both be zero,
 	// and this function will return false.
 	const mask = 0 |
 		(1<<26-1)<<'A' |
 		(1<<26-1)<<'a' |
 		(1<<10-1)<<'0' |
 		1<<'_'

 	return ((uint64(1)<<c)&(mask&(1<<64-1)) |
 		(uint64(1)<<(c-64))&(mask>>64)) != 0
 }
	// Copyright 2024 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 relnote

	import (
	"fmt"
	"strings"
	"unicode"
	"unicode/utf8"

	"golang.org/x/mod/module"
	md "rsc.io/markdown"
	)

	// addSymbolLinks looks for text like [Buffer] and
	// [math.Max] and replaces them with links to standard library
	// symbols and packages.
	// It uses the given default package for links without a package.
	func addSymbolLinks(doc *md.Document, defaultPackage string) {
	addSymbolLinksBlocks(doc.Blocks, defaultPackage)
	}

	func addSymbolLinksBlocks(bs []md.Block, defaultPackage string) {
	for _, b := range bs {
	addSymbolLinksBlock(b, defaultPackage)
	}
	}

	func addSymbolLinksBlock(b md.Block, defaultPackage string) {
	switch b := b.(type) {
	case *md.Heading:
	addSymbolLinksBlock(b.Text, defaultPackage)
	case *md.Text:
	b.Inline = addSymbolLinksInlines(b.Inline, defaultPackage)
	case *md.List:
	addSymbolLinksBlocks(b.Items, defaultPackage)
	case *md.Item:
	addSymbolLinksBlocks(b.Blocks, defaultPackage)
	case *md.Paragraph:
	addSymbolLinksBlock(b.Text, defaultPackage)
	case *md.Quote:
	addSymbolLinksBlocks(b.Blocks, defaultPackage)
	// no links in these blocks
	case *md.CodeBlock:
	case *md.HTMLBlock:
	case *md.Empty:
	case *md.ThematicBreak:
	default:
	panic(fmt.Sprintf("unknown block type %T", b))
	}
	}

	// addSymbolLinksInlines looks for symbol links in the slice of inline markdown
	// elements. It returns a new slice of inline elements with links added.
	func addSymbolLinksInlines(ins []md.Inline, defaultPackage string) []md.Inline {
	ins = splitAtBrackets(ins)
	var res []md.Inline
	for i := 0; i < len(ins); i++ {
	if txt := symbolLinkText(i, ins); txt != "" {
	link, ok := symbolLink(txt, defaultPackage)
	if ok {
	res = append(res, link)
	i += 2
	continue
	}
	}

	switch in := ins[i].(type) {
	case *md.Strong:
	res = append(res, addSymbolLinksInlines(in.Inner, defaultPackage)...)
	case *md.Emph:
	res = append(res, addSymbolLinksInlines(in.Inner, defaultPackage)...)
	case *md.Del:
	res = append(res, addSymbolLinksInlines(in.Inner, defaultPackage)...)
	// Don't look for links in anything else.
	default:
	res = append(res, in)
	}
	}
	return res
	}

	// splitAtBrackets rewrites ins so that every '[' and ']' is the only character
	// of its Plain.
	// For example, the element
	//
	// [Plain("the [Buffer] is")]
	//
	// is rewritten to
	//
	// [Plain("the "), Plain("["), Plain("Buffer"), Plain("]"), Plain(" is")]
	//
	// This transformation simplifies looking for symbol links.
	func splitAtBrackets(ins []md.Inline) []md.Inline {
	var res []md.Inline
	for _, in := range ins {
	if p, ok := in.(*md.Plain); ok {
	text := p.Text
	for len(text) > 0 {
	i := strings.IndexAny(text, "[]")
	// If there are no brackets, the remaining text is a single
	// Plain and we are done.
	if i < 0 {
	res = append(res, &md.Plain{Text: text})
	break
	}
	// There is a bracket; make Plains for it and the text before it (if any).
	if i > 0 {
	res = append(res, &md.Plain{Text: text[:i]})
	}
	res = append(res, &md.Plain{Text: text[i : i+1]})
	text = text[i+1:]
	}
	} else {
	res = append(res, in)
	}
	}
	return res
	}

	// symbolLinkText returns the text of a possible symbol link.
	// It is given a slice of Inline elements and an index into the slice.
	// If the index refers to a sequence of elements
	//
	// [Plain("["), Plain_or_Code(text), Plain("]")]
	//
	// and the brackets are adjacent to the right kind of runes for a link, then
	// symbolLinkText returns the text of the middle element.
	// Otherwise it returns the empty string.
	func symbolLinkText(i int, ins []md.Inline) string {
	// plainText returns the text of ins[j] if it is a Plain element, or "" otherwise.
	plainText := func(j int) string {
	if j < 0 \|\| j >= len(ins) {
	return ""
	}
	if p, ok := ins[j].(*md.Plain); ok {
	return p.Text
	}
	return ""
	}

	// ins[i] must be a "[".
	if plainText(i) != "[" {
	return ""
	}
	// The open bracket must be preceeded by a link-adjacent rune (or by nothing).
	if t := plainText(i - 1); t != "" {
	r, _ := utf8.DecodeLastRuneInString(t)
	if !isLinkAdjacentRune(r) {
	return ""
	}
	}
	// The element after the next must be a ']'.
	if plainText(i+2) != "]" {
	return ""
	}
	// The ']' must be followed by a link-adjacent rune (or by nothing).
	if t := plainText(i + 3); t != "" {
	r, _ := utf8.DecodeRuneInString(t)
	if !isLinkAdjacentRune(r) {
	return ""
	}
	}

	// ins[i+1] must be a Plain or a Code.
	// Its text is the symbol to link to.
	if i+1 >= len(ins) {
	return ""
	}
	switch in := ins[i+1].(type) {
	case *md.Plain:
	return in.Text
	case *md.Code:
	return in.Text
	default:
	return ""
	}
	}

	// symbolLink converts s into a Link and returns it and true, or nil and false if
	// s is not a valid link or is surrounded by runes that disqualify it from being
	// converted to a link.
	//
	// The argument s is the text between '[' and ']'.
	func symbolLink(s, defaultPackage string) (md.Inline, bool) {
	pkg, sym, ok := splitRef(s)
	if !ok {
	return nil, false
	}
	if pkg == "" {
	if defaultPackage == "" {
	return nil, false
	}
	pkg = defaultPackage
	}
	if sym != "" {
	sym = "#" + sym
	}
	return &md.Link{
	Inner: []md.Inline{&md.Code{Text: s}},
	URL: fmt.Sprintf("/pkg/%s%s", pkg, sym),
	}, true
	}

	// isLinkAdjacentRune reports whether r can be adjacent to a symbol link.
	// The logic is the same as the go/doc/comment package.
	func isLinkAdjacentRune(r rune) bool {
	return unicode.IsPunct(r) \|\| r == ' ' \|\| r == '\t' \|\| r == '\n'
	}

	// splitRef splits s into a package and possibly a symbol.
	// Examples:
	//
	// splitRef("math.Max") => ("math", "Max", true)
	// splitRef("bytes.Buffer.String") => ("bytes", "Buffer.String", true)
	// splitRef("math") => ("math", "", true)
	func splitRef(s string) (pkg, name string, ok bool) {
	s = strings.TrimPrefix(s, "*")
	pkg, name, ok = splitDocName(s)
	var recv string
	if ok {
	pkg, recv, _ = splitDocName(pkg)
	}
	if pkg != "" {
	if err := module.CheckImportPath(pkg); err != nil {
	return "", "", false
	}
	}
	if recv != "" {
	name = recv + "." + name
	}
	return pkg, name, true
	}

	// The following functions were copied from go/doc/comment/parse.go.

	// If text is of the form before.Name, where Name is a capitalized Go identifier,
	// then splitDocName returns before, name, true.
	// Otherwise it returns text, "", false.
	func splitDocName(text string) (before, name string, foundDot bool) {
	i := strings.LastIndex(text, ".")
	name = text[i+1:]
	if !isName(name) {
	return text, "", false
	}
	if i >= 0 {
	before = text[:i]
	}
	return before, name, true
	}

	// isName reports whether s is a capitalized Go identifier (like Name).
	func isName(s string) bool {
	t, ok := ident(s)
	if !ok \|\| t != s {
	return false
	}
	r, _ := utf8.DecodeRuneInString(s)
	return unicode.IsUpper(r)
	}

	// ident checks whether s begins with a Go identifier.
	// If so, it returns the identifier, which is a prefix of s, and ok == true.
	// Otherwise it returns "", false.
	// The caller should skip over the first len(id) bytes of s
	// before further processing.
	func ident(s string) (id string, ok bool) {
	// Scan [\pL_][\pL_0-9]*
	n := 0
	for n < len(s) {
	if c := s[n]; c < utf8.RuneSelf {
	if isIdentASCII(c) && (n > 0 \|\| c < '0' \|\| c > '9') {
	n++
	continue
	}
	break
	}
	r, nr := utf8.DecodeRuneInString(s[n:])
	if unicode.IsLetter(r) {
	n += nr
	continue
	}
	break
	}
	return s[:n], n > 0
	}

	// isIdentASCII reports whether c is an ASCII identifier byte.
	func isIdentASCII(c byte) bool {
	// mask is a 128-bit bitmap with 1s for allowed bytes,
	// so that the byte c can be tested with a shift and an and.
	// If c > 128, then 1<<c and 1<<(c-64) will both be zero,
	// and this function will return false.
	const mask = 0 \|
	(1<<26-1)<<'A' \|
	(1<<26-1)<<'a' \|
	(1<<10-1)<<'0' \|
	1<<'_'

	return ((uint64(1)<<c)&(mask&(1<<64-1)) \|
	(uint64(1)<<(c-64))&(mask>>64)) != 0
	}