gopls/internal/lsp/template/completion.go - tools - Git at Google

 // Copyright 2021 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 template

 import (
 	"bytes"
 	"context"
 	"fmt"
 	"go/scanner"
 	"go/token"
 	"strings"

 	"golang.org/x/tools/gopls/internal/lsp/protocol"
 	"golang.org/x/tools/gopls/internal/lsp/source"
 )

 // information needed for completion
 type completer struct {
 	p      *Parsed
 	pos    protocol.Position
 	offset int // offset of the start of the Token
 	ctx    protocol.CompletionContext
 	syms   map[string]symbol
 }

 func Completion(ctx context.Context, snapshot source.Snapshot, fh source.VersionedFileHandle, pos protocol.Position, context protocol.CompletionContext) (*protocol.CompletionList, error) {
 	all := New(snapshot.Templates())
 	var start int // the beginning of the Token (completed or not)
 	syms := make(map[string]symbol)
 	var p *Parsed
 	for fn, fc := range all.files {
 		// collect symbols from all template files
 		filterSyms(syms, fc.symbols)
 		if fn.Filename() != fh.URI().Filename() {
 			continue
 		}
 		if start = inTemplate(fc, pos); start == -1 {
 			return nil, nil
 		}
 		p = fc
 	}
 	if p == nil {
 		// this cannot happen unless the search missed a template file
 		return nil, fmt.Errorf("%s not found", fh.FileIdentity().URI.Filename())
 	}
 	c := completer{
 		p:      p,
 		pos:    pos,
 		offset: start + len(Left),
 		ctx:    context,
 		syms:   syms,
 	}
 	return c.complete()
 }

 func filterSyms(syms map[string]symbol, ns []symbol) {
 	for _, xsym := range ns {
 		switch xsym.kind {
 		case protocol.Method, protocol.Package, protocol.Boolean, protocol.Namespace,
 			protocol.Function:
 			syms[xsym.name] = xsym // we don't care which symbol we get
 		case protocol.Variable:
 			if xsym.name != "dot" {
 				syms[xsym.name] = xsym
 			}
 		case protocol.Constant:
 			if xsym.name == "nil" {
 				syms[xsym.name] = xsym
 			}
 		}
 	}
 }

 // return the starting position of the enclosing token, or -1 if none
 func inTemplate(fc *Parsed, pos protocol.Position) int {
 	// pos is the pos-th character. if the cursor is at the beginning
 	// of the file, pos is 0. That is, we've only seen characters before pos
 	// 1. pos might be in a Token, return tk.Start
 	// 2. pos might be after an elided but before a Token, return elided
 	// 3. return -1 for false
 	offset := fc.FromPosition(pos)
 	// this could be a binary search, as the tokens are ordered
 	for _, tk := range fc.tokens {
 		if tk.Start < offset && offset <= tk.End {
 			return tk.Start
 		}
 	}
 	for _, x := range fc.elided {
 		if x > offset {
 			// fc.elided is sorted
 			break
 		}
 		// If the interval [x,offset] does not contain Left or Right
 		// then provide completions. (do we need the test for Right?)
 		if !bytes.Contains(fc.buf[x:offset], []byte(Left)) && !bytes.Contains(fc.buf[x:offset], []byte(Right)) {
 			return x
 		}
 	}
 	return -1
 }

 var (
 	keywords = []string{"if", "with", "else", "block", "range", "template", "end}}", "end"}
 	globals  = []string{"and", "call", "html", "index", "slice", "js", "len", "not", "or",
 		"urlquery", "printf", "println", "print", "eq", "ne", "le", "lt", "ge", "gt"}
 )

 // find the completions. start is the offset of either the Token enclosing pos, or where
 // the incomplete token starts.
 // The error return is always nil.
 func (c *completer) complete() (*protocol.CompletionList, error) {
 	ans := &protocol.CompletionList{IsIncomplete: true, Items: []protocol.CompletionItem{}}
 	start := c.p.FromPosition(c.pos)
 	sofar := c.p.buf[c.offset:start]
 	if len(sofar) == 0 || sofar[len(sofar)-1] == ' ' || sofar[len(sofar)-1] == '\t' {
 		return ans, nil
 	}
 	// sofar could be parsed by either c.analyzer() or scan(). The latter is precise
 	// and slower, but fast enough
 	words := scan(sofar)
 	// 1. if pattern starts $, show variables
 	// 2. if pattern starts ., show methods (and . by itself?)
 	// 3. if len(words) == 1, show firstWords (but if it were a |, show functions and globals)
 	// 4. ...? (parenthetical expressions, arguments, ...) (packages, namespaces, nil?)
 	if len(words) == 0 {
 		return nil, nil // if this happens, why were we called?
 	}
 	pattern := string(words[len(words)-1])
 	if pattern[0] == '$' {
 		// should we also return a raw "$"?
 		for _, s := range c.syms {
 			if s.kind == protocol.Variable && weakMatch(s.name, pattern) > 0 {
 				ans.Items = append(ans.Items, protocol.CompletionItem{
 					Label:  s.name,
 					Kind:   protocol.VariableCompletion,
 					Detail: "Variable",
 				})
 			}
 		}
 		return ans, nil
 	}
 	if pattern[0] == '.' {
 		for _, s := range c.syms {
 			if s.kind == protocol.Method && weakMatch("."+s.name, pattern) > 0 {
 				ans.Items = append(ans.Items, protocol.CompletionItem{
 					Label:  s.name,
 					Kind:   protocol.MethodCompletion,
 					Detail: "Method/member",
 				})
 			}
 		}
 		return ans, nil
 	}
 	// could we get completion attempts in strings or numbers, and if so, do we care?
 	// globals
 	for _, kw := range globals {
 		if weakMatch(kw, string(pattern)) != 0 {
 			ans.Items = append(ans.Items, protocol.CompletionItem{
 				Label:  kw,
 				Kind:   protocol.KeywordCompletion,
 				Detail: "Function",
 			})
 		}
 	}
 	// and functions
 	for _, s := range c.syms {
 		if s.kind == protocol.Function && weakMatch(s.name, pattern) != 0 {
 			ans.Items = append(ans.Items, protocol.CompletionItem{
 				Label:  s.name,
 				Kind:   protocol.FunctionCompletion,
 				Detail: "Function",
 			})
 		}
 	}
 	// keywords if we're at the beginning
 	if len(words) <= 1 || len(words[len(words)-2]) == 1 && words[len(words)-2][0] == '|' {
 		for _, kw := range keywords {
 			if weakMatch(kw, string(pattern)) != 0 {
 				ans.Items = append(ans.Items, protocol.CompletionItem{
 					Label:  kw,
 					Kind:   protocol.KeywordCompletion,
 					Detail: "keyword",
 				})
 			}
 		}
 	}
 	return ans, nil
 }

 // someday think about comments, strings, backslashes, etc
 // this would repeat some of the template parsing, but because the user is typing
 // there may be no parse tree here.
 // (go/scanner will report 2 tokens for $a, as $ is not a legal go identifier character)
 // (go/scanner is about 2.7 times more expensive)
 func (c *completer) analyze(buf []byte) [][]byte {
 	// we want to split on whitespace and before dots
 	var working []byte
 	var ans [][]byte
 	for _, ch := range buf {
 		if ch == '.' && len(working) > 0 {
 			ans = append(ans, working)
 			working = []byte{'.'}
 			continue
 		}
 		if ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r' {
 			if len(working) > 0 {
 				ans = append(ans, working)
 				working = []byte{}
 				continue
 			}
 		}
 		working = append(working, ch)
 	}
 	if len(working) > 0 {
 		ans = append(ans, working)
 	}
 	ch := buf[len(buf)-1]
 	if ch == ' ' || ch == '\t' {
 		// avoid completing on whitespace
 		ans = append(ans, []byte{ch})
 	}
 	return ans
 }

 // version of c.analyze that uses go/scanner.
 func scan(buf []byte) []string {
 	fset := token.NewFileSet()
 	fp := fset.AddFile("", -1, len(buf))
 	var sc scanner.Scanner
 	sc.Init(fp, buf, func(pos token.Position, msg string) {}, scanner.ScanComments)
 	ans := make([]string, 0, 10) // preallocating gives a measurable savings
 	for {
 		_, tok, lit := sc.Scan() // tok is an int
 		if tok == token.EOF {
 			break // done
 		} else if tok == token.SEMICOLON && lit == "\n" {
 			continue // don't care, but probably can't happen
 		} else if tok == token.PERIOD {
 			ans = append(ans, ".") // lit is empty
 		} else if tok == token.IDENT && len(ans) > 0 && ans[len(ans)-1] == "." {
 			ans[len(ans)-1] = "." + lit
 		} else if tok == token.IDENT && len(ans) > 0 && ans[len(ans)-1] == "$" {
 			ans[len(ans)-1] = "$" + lit
 		} else if lit != "" {
 			ans = append(ans, lit)
 		}
 	}
 	return ans
 }

 // pattern is what the user has typed
 func weakMatch(choice, pattern string) float64 {
 	lower := strings.ToLower(choice)
 	// for now, use only lower-case everywhere
 	pattern = strings.ToLower(pattern)
 	// The first char has to match
 	if pattern[0] != lower[0] {
 		return 0
 	}
 	// If they start with ., then the second char has to match
 	from := 1
 	if pattern[0] == '.' {
 		if len(pattern) < 2 {
 			return 1 // pattern just a ., so it matches
 		}
 		if pattern[1] != lower[1] {
 			return 0
 		}
 		from = 2
 	}
 	// check that all the characters of pattern occur as a subsequence of choice
 	i, j := from, from
 	for ; i < len(lower) && j < len(pattern); j++ {
 		if pattern[j] == lower[i] {
 			i++
 			if i >= len(lower) {
 				return 0
 			}
 		}
 	}
 	if j < len(pattern) {
 		return 0
 	}
 	return 1
 }
	// Copyright 2021 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 template

	import (
	"bytes"
	"context"
	"fmt"
	"go/scanner"
	"go/token"
	"strings"

	"golang.org/x/tools/gopls/internal/lsp/protocol"
	"golang.org/x/tools/gopls/internal/lsp/source"
	)

	// information needed for completion
	type completer struct {
	p *Parsed
	pos protocol.Position
	offset int // offset of the start of the Token
	ctx protocol.CompletionContext
	syms map[string]symbol
	}

	func Completion(ctx context.Context, snapshot source.Snapshot, fh source.VersionedFileHandle, pos protocol.Position, context protocol.CompletionContext) (*protocol.CompletionList, error) {
	all := New(snapshot.Templates())
	var start int // the beginning of the Token (completed or not)
	syms := make(map[string]symbol)
	var p *Parsed
	for fn, fc := range all.files {
	// collect symbols from all template files
	filterSyms(syms, fc.symbols)
	if fn.Filename() != fh.URI().Filename() {
	continue
	}
	if start = inTemplate(fc, pos); start == -1 {
	return nil, nil
	}
	p = fc
	}
	if p == nil {
	// this cannot happen unless the search missed a template file
	return nil, fmt.Errorf("%s not found", fh.FileIdentity().URI.Filename())
	}
	c := completer{
	p: p,
	pos: pos,
	offset: start + len(Left),
	ctx: context,
	syms: syms,
	}
	return c.complete()
	}

	func filterSyms(syms map[string]symbol, ns []symbol) {
	for _, xsym := range ns {
	switch xsym.kind {
	case protocol.Method, protocol.Package, protocol.Boolean, protocol.Namespace,
	protocol.Function:
	syms[xsym.name] = xsym // we don't care which symbol we get
	case protocol.Variable:
	if xsym.name != "dot" {
	syms[xsym.name] = xsym
	}
	case protocol.Constant:
	if xsym.name == "nil" {
	syms[xsym.name] = xsym
	}
	}
	}
	}

	// return the starting position of the enclosing token, or -1 if none
	func inTemplate(fc *Parsed, pos protocol.Position) int {
	// pos is the pos-th character. if the cursor is at the beginning
	// of the file, pos is 0. That is, we've only seen characters before pos
	// 1. pos might be in a Token, return tk.Start
	// 2. pos might be after an elided but before a Token, return elided
	// 3. return -1 for false
	offset := fc.FromPosition(pos)
	// this could be a binary search, as the tokens are ordered
	for _, tk := range fc.tokens {
	if tk.Start < offset && offset <= tk.End {
	return tk.Start
	}
	}
	for _, x := range fc.elided {
	if x > offset {
	// fc.elided is sorted
	break
	}
	// If the interval [x,offset] does not contain Left or Right
	// then provide completions. (do we need the test for Right?)
	if !bytes.Contains(fc.buf[x:offset], []byte(Left)) && !bytes.Contains(fc.buf[x:offset], []byte(Right)) {
	return x
	}
	}
	return -1
	}

	var (
	keywords = []string{"if", "with", "else", "block", "range", "template", "end}}", "end"}
	globals = []string{"and", "call", "html", "index", "slice", "js", "len", "not", "or",
	"urlquery", "printf", "println", "print", "eq", "ne", "le", "lt", "ge", "gt"}
	)

	// find the completions. start is the offset of either the Token enclosing pos, or where
	// the incomplete token starts.
	// The error return is always nil.
	func (c completer) complete() (protocol.CompletionList, error) {
	ans := &protocol.CompletionList{IsIncomplete: true, Items: []protocol.CompletionItem{}}
	start := c.p.FromPosition(c.pos)
	sofar := c.p.buf[c.offset:start]
	if len(sofar) == 0 \|\| sofar[len(sofar)-1] == ' ' \|\| sofar[len(sofar)-1] == '\t' {
	return ans, nil
	}
	// sofar could be parsed by either c.analyzer() or scan(). The latter is precise
	// and slower, but fast enough
	words := scan(sofar)
	// 1. if pattern starts $, show variables
	// 2. if pattern starts ., show methods (and . by itself?)
	// 3. if len(words) == 1, show firstWords (but if it were a \|, show functions and globals)
	// 4. ...? (parenthetical expressions, arguments, ...) (packages, namespaces, nil?)
	if len(words) == 0 {
	return nil, nil // if this happens, why were we called?
	}
	pattern := string(words[len(words)-1])
	if pattern[0] == '$' {
	// should we also return a raw "$"?
	for _, s := range c.syms {
	if s.kind == protocol.Variable && weakMatch(s.name, pattern) > 0 {
	ans.Items = append(ans.Items, protocol.CompletionItem{
	Label: s.name,
	Kind: protocol.VariableCompletion,
	Detail: "Variable",
	})
	}
	}
	return ans, nil
	}
	if pattern[0] == '.' {
	for _, s := range c.syms {
	if s.kind == protocol.Method && weakMatch("."+s.name, pattern) > 0 {
	ans.Items = append(ans.Items, protocol.CompletionItem{
	Label: s.name,
	Kind: protocol.MethodCompletion,
	Detail: "Method/member",
	})
	}
	}
	return ans, nil
	}
	// could we get completion attempts in strings or numbers, and if so, do we care?
	// globals
	for _, kw := range globals {
	if weakMatch(kw, string(pattern)) != 0 {
	ans.Items = append(ans.Items, protocol.CompletionItem{
	Label: kw,
	Kind: protocol.KeywordCompletion,
	Detail: "Function",
	})
	}
	}
	// and functions
	for _, s := range c.syms {
	if s.kind == protocol.Function && weakMatch(s.name, pattern) != 0 {
	ans.Items = append(ans.Items, protocol.CompletionItem{
	Label: s.name,
	Kind: protocol.FunctionCompletion,
	Detail: "Function",
	})
	}
	}
	// keywords if we're at the beginning
	if len(words) <= 1 \|\| len(words[len(words)-2]) == 1 && words[len(words)-2][0] == '\|' {
	for _, kw := range keywords {
	if weakMatch(kw, string(pattern)) != 0 {
	ans.Items = append(ans.Items, protocol.CompletionItem{
	Label: kw,
	Kind: protocol.KeywordCompletion,
	Detail: "keyword",
	})
	}
	}
	}
	return ans, nil
	}

	// someday think about comments, strings, backslashes, etc
	// this would repeat some of the template parsing, but because the user is typing
	// there may be no parse tree here.
	// (go/scanner will report 2 tokens for $a, as $ is not a legal go identifier character)
	// (go/scanner is about 2.7 times more expensive)
	func (c *completer) analyze(buf []byte) [][]byte {
	// we want to split on whitespace and before dots
	var working []byte
	var ans [][]byte
	for _, ch := range buf {
	if ch == '.' && len(working) > 0 {
	ans = append(ans, working)
	working = []byte{'.'}
	continue
	}
	if ch == ' ' \|\| ch == '\t' \|\| ch == '\n' \|\| ch == '\r' {
	if len(working) > 0 {
	ans = append(ans, working)
	working = []byte{}
	continue
	}
	}
	working = append(working, ch)
	}
	if len(working) > 0 {
	ans = append(ans, working)
	}
	ch := buf[len(buf)-1]
	if ch == ' ' \|\| ch == '\t' {
	// avoid completing on whitespace
	ans = append(ans, []byte{ch})
	}
	return ans
	}

	// version of c.analyze that uses go/scanner.
	func scan(buf []byte) []string {
	fset := token.NewFileSet()
	fp := fset.AddFile("", -1, len(buf))
	var sc scanner.Scanner
	sc.Init(fp, buf, func(pos token.Position, msg string) {}, scanner.ScanComments)
	ans := make([]string, 0, 10) // preallocating gives a measurable savings
	for {
	_, tok, lit := sc.Scan() // tok is an int
	if tok == token.EOF {
	break // done
	} else if tok == token.SEMICOLON && lit == "\n" {
	continue // don't care, but probably can't happen
	} else if tok == token.PERIOD {
	ans = append(ans, ".") // lit is empty
	} else if tok == token.IDENT && len(ans) > 0 && ans[len(ans)-1] == "." {
	ans[len(ans)-1] = "." + lit
	} else if tok == token.IDENT && len(ans) > 0 && ans[len(ans)-1] == "$" {
	ans[len(ans)-1] = "$" + lit
	} else if lit != "" {
	ans = append(ans, lit)
	}
	}
	return ans
	}

	// pattern is what the user has typed
	func weakMatch(choice, pattern string) float64 {
	lower := strings.ToLower(choice)
	// for now, use only lower-case everywhere
	pattern = strings.ToLower(pattern)
	// The first char has to match
	if pattern[0] != lower[0] {
	return 0
	}
	// If they start with ., then the second char has to match
	from := 1
	if pattern[0] == '.' {
	if len(pattern) < 2 {
	return 1 // pattern just a ., so it matches
	}
	if pattern[1] != lower[1] {
	return 0
	}
	from = 2
	}
	// check that all the characters of pattern occur as a subsequence of choice
	i, j := from, from
	for ; i < len(lower) && j < len(pattern); j++ {
	if pattern[j] == lower[i] {
	i++
	if i >= len(lower) {
	return 0
	}
	}
	}
	if j < len(pattern) {
	return 0
	}
	return 1
	}