internal/lsp/source/completion_literal.go - tools - Git at Google

 // Copyright 2019 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 source

 import (
 	"go/ast"
 	"go/token"
 	"go/types"
 	"strings"
 	"unicode"

 	"golang.org/x/tools/internal/lsp/diff"
 	"golang.org/x/tools/internal/lsp/protocol"
 	"golang.org/x/tools/internal/lsp/snippet"
 	"golang.org/x/tools/internal/span"
 	"golang.org/x/tools/internal/telemetry/log"
 )

 // literal generates composite literal, function literal, and make()
 // completion items.
 func (c *completer) literal(literalType types.Type, imp *importInfo) {
 	if c.expectedType.objType == nil {
 		return
 	}

 	// Don't provide literal candidates for variadic function arguments.
 	// For example, don't provide "[]interface{}{}" in "fmt.Print(<>)".
 	if c.expectedType.variadic {
 		return
 	}

 	// Avoid literal candidates if the expected type is an empty
 	// interface. It isn't very useful to suggest a literal candidate of
 	// every possible type.
 	if isEmptyInterface(c.expectedType.objType) {
 		return
 	}

 	// We handle unnamed literal completions explicitly before searching
 	// for candidates. Avoid named-type literal completions for
 	// unnamed-type expected type since that results in duplicate
 	// candidates. For example, in
 	//
 	// type mySlice []int
 	// var []int = <>
 	//
 	// don't offer "mySlice{}" since we have already added a candidate
 	// of "[]int{}".
 	if _, named := literalType.(*types.Named); named {
 		if _, named := deref(c.expectedType.objType).(*types.Named); !named {
 			return
 		}
 	}

 	// Check if an object of type literalType or *literalType would
 	// match our expected type.
 	if !c.matchingType(literalType) {
 		literalType = types.NewPointer(literalType)

 		if !c.matchingType(literalType) {
 			return
 		}
 	}

 	ptr, isPointer := literalType.(*types.Pointer)
 	if isPointer {
 		literalType = ptr.Elem()
 	}

 	var (
 		qf  = c.qf
 		sel = enclosingSelector(c.path, c.pos)
 	)

 	// Don't qualify the type name if we are in a selector expression
 	// since the package name is already present.
 	if sel != nil {
 		qf = func(_ *types.Package) string { return "" }
 	}

 	typeName := types.TypeString(literalType, qf)

 	// A type name of "[]int" doesn't work very will with the matcher
 	// since "[" isn't a valid identifier prefix. Here we strip off the
 	// slice (and array) prefix yielding just "int".
 	matchName := typeName
 	switch t := literalType.(type) {
 	case *types.Slice:
 		matchName = types.TypeString(t.Elem(), qf)
 	case *types.Array:
 		matchName = types.TypeString(t.Elem(), qf)
 	}

 	addlEdits, err := c.importEdits(imp)
 	if err != nil {
 		log.Error(c.ctx, "error adding import for literal candidate", err)
 		return
 	}

 	// If prefix matches the type name, client may want a composite literal.
 	if score := c.matcher.Score(matchName); score >= 0 {
 		if isPointer {
 			if sel != nil {
 				// If we are in a selector we must place the "&" before the selector.
 				// For example, "foo.B<>" must complete to "&foo.Bar{}", not
 				// "foo.&Bar{}".
 				edits, err := referenceEdit(c.view.Session().Cache().FileSet(), c.mapper, sel)
 				if err != nil {
 					log.Error(c.ctx, "error making edit for literal pointer completion", err)
 					return
 				}
 				addlEdits = append(addlEdits, edits...)
 			} else {
 				// Otherwise we can stick the "&" directly before the type name.
 				typeName = "&" + typeName
 			}
 		}

 		switch t := literalType.Underlying().(type) {
 		case *types.Struct, *types.Array, *types.Slice, *types.Map:
 			c.compositeLiteral(t, typeName, float64(score), addlEdits)
 		case *types.Basic:
 			// Add a literal completion for basic types that implement our
 			// expected interface (e.g. named string type http.Dir
 			// implements http.FileSystem).
 			if isInterface(c.expectedType.objType) {
 				c.basicLiteral(t, typeName, float64(score), addlEdits)
 			}
 		}
 	}

 	// If prefix matches "make", client may want a "make()"
 	// invocation. We also include the type name to allow for more
 	// flexible fuzzy matching.
 	if score := c.matcher.Score("make." + matchName); !isPointer && score >= 0 {
 		switch literalType.Underlying().(type) {
 		case *types.Slice:
 			// The second argument to "make()" for slices is required, so default to "0".
 			c.makeCall(typeName, "0", float64(score), addlEdits)
 		case *types.Map, *types.Chan:
 			// Maps and channels don't require the second argument, so omit
 			// to keep things simple for now.
 			c.makeCall(typeName, "", float64(score), addlEdits)
 		}
 	}

 	// If prefix matches "func", client may want a function literal.
 	if score := c.matcher.Score("func"); !isPointer && score >= 0 {
 		switch t := literalType.Underlying().(type) {
 		case *types.Signature:
 			c.functionLiteral(t, float64(score))
 		}
 	}
 }

 // referenceEdit produces text edits that prepend a "&" operator to the
 // specified node.
 func referenceEdit(fset *token.FileSet, m *protocol.ColumnMapper, node ast.Node) ([]protocol.TextEdit, error) {
 	rng := span.Range{
 		FileSet: fset,
 		Start:   node.Pos(),
 		End:     node.Pos(),
 	}
 	spn, err := rng.Span()
 	if err != nil {
 		return nil, err
 	}
 	return ToProtocolEdits(m, []diff.TextEdit{{
 		Span:    spn,
 		NewText: "&",
 	}})
 }

 // literalCandidateScore is the base score for literal candidates.
 // Literal candidates match the expected type so they should be high
 // scoring, but we want them ranked below lexical objects of the
 // correct type, so scale down highScore.
 const literalCandidateScore = highScore / 2

 // functionLiteral adds a function literal completion item for the
 // given signature.
 func (c *completer) functionLiteral(sig *types.Signature, matchScore float64) {
 	snip := &snippet.Builder{}
 	snip.WriteText("func(")
 	seenParamNames := make(map[string]bool)
 	for i := 0; i < sig.Params().Len(); i++ {
 		if i > 0 {
 			snip.WriteText(", ")
 		}

 		p := sig.Params().At(i)
 		name := p.Name()

 		// If the parameter has no name in the signature, we need to try
 		// come up with a parameter name.
 		if name == "" {
 			// Our parameter names are guesses, so they must be placeholders
 			// for easy correction. If placeholders are disabled, don't
 			// offer the completion.
 			if !c.opts.Placeholders {
 				return
 			}

 			// Try abbreviating named types. If the type isn't named, or the
 			// abbreviation duplicates a previous name, give up and use
 			// "_". The user will have to provide a name for this parameter
 			// in order to use it.
 			if named, ok := deref(p.Type()).(*types.Named); ok {
 				name = abbreviateCamel(named.Obj().Name())
 				if seenParamNames[name] {
 					name = "_"
 				} else {
 					seenParamNames[name] = true
 				}
 			} else {
 				name = "_"
 			}
 			snip.WritePlaceholder(func(b *snippet.Builder) {
 				b.WriteText(name)
 			})
 		} else {
 			snip.WriteText(name)
 		}

 		// If the following param's type is identical to this one, omit
 		// this param's type string. For example, emit "i, j int" instead
 		// of "i int, j int".
 		if i == sig.Params().Len()-1 || !types.Identical(p.Type(), sig.Params().At(i+1).Type()) {
 			snip.WriteText(" ")
 			typeStr := types.TypeString(p.Type(), c.qf)
 			if sig.Variadic() && i == sig.Params().Len()-1 {
 				typeStr = strings.Replace(typeStr, "[]", "...", 1)
 			}
 			snip.WriteText(typeStr)
 		}
 	}
 	snip.WriteText(")")

 	results := sig.Results()
 	if results.Len() > 0 {
 		snip.WriteText(" ")
 	}

 	resultsNeedParens := results.Len() > 1 ||
 		results.Len() == 1 && results.At(0).Name() != ""

 	if resultsNeedParens {
 		snip.WriteText("(")
 	}
 	for i := 0; i < results.Len(); i++ {
 		if i > 0 {
 			snip.WriteText(", ")
 		}
 		r := results.At(i)
 		if name := r.Name(); name != "" {
 			snip.WriteText(name + " ")
 		}
 		snip.WriteText(types.TypeString(r.Type(), c.qf))
 	}
 	if resultsNeedParens {
 		snip.WriteText(")")
 	}

 	snip.WriteText(" {")
 	snip.WriteFinalTabstop()
 	snip.WriteText("}")

 	c.items = append(c.items, CompletionItem{
 		Label:   "func(...) {}",
 		Score:   matchScore * literalCandidateScore,
 		Kind:    protocol.VariableCompletion,
 		snippet: snip,
 	})
 }

 // abbreviateCamel abbreviates camel case identifiers into
 // abbreviations. For example, "fooBar" is abbreviated "fb".
 func abbreviateCamel(s string) string {
 	var (
 		b            strings.Builder
 		useNextUpper bool
 	)
 	for i, r := range s {
 		if i == 0 {
 			b.WriteRune(unicode.ToLower(r))
 		}

 		if unicode.IsUpper(r) {
 			if useNextUpper {
 				b.WriteRune(unicode.ToLower(r))
 				useNextUpper = false
 			}
 		} else {
 			useNextUpper = true
 		}
 	}

 	return b.String()
 }

 // compositeLiteral adds a composite literal completion item for the given typeName.
 func (c *completer) compositeLiteral(T types.Type, typeName string, matchScore float64, edits []protocol.TextEdit) {
 	snip := &snippet.Builder{}
 	snip.WriteText(typeName + "{")
 	// Don't put the tab stop inside the composite literal curlies "{}"
 	// for structs that have no fields.
 	if strct, ok := T.(*types.Struct); !ok || strct.NumFields() > 0 {
 		snip.WriteFinalTabstop()
 	}
 	snip.WriteText("}")

 	nonSnippet := typeName + "{}"

 	c.items = append(c.items, CompletionItem{
 		Label:               nonSnippet,
 		InsertText:          nonSnippet,
 		Score:               matchScore * literalCandidateScore,
 		Kind:                protocol.VariableCompletion,
 		AdditionalTextEdits: edits,
 		snippet:             snip,
 	})
 }

 // basicLiteral adds a literal completion item for the given basic
 // type name typeName.
 func (c *completer) basicLiteral(T types.Type, typeName string, matchScore float64, edits []protocol.TextEdit) {
 	snip := &snippet.Builder{}
 	snip.WriteText(typeName + "(")
 	snip.WriteFinalTabstop()
 	snip.WriteText(")")

 	nonSnippet := typeName + "()"

 	c.items = append(c.items, CompletionItem{
 		Label:               nonSnippet,
 		InsertText:          nonSnippet,
 		Detail:              T.String(),
 		Score:               matchScore * literalCandidateScore,
 		Kind:                protocol.VariableCompletion,
 		AdditionalTextEdits: edits,
 		snippet:             snip,
 	})
 }

 // makeCall adds a completion item for a "make()" call given a specific type.
 func (c *completer) makeCall(typeName string, secondArg string, matchScore float64, edits []protocol.TextEdit) {
 	// Keep it simple and don't add any placeholders for optional "make()" arguments.

 	snip := &snippet.Builder{}
 	snip.WriteText("make(" + typeName)
 	if secondArg != "" {
 		snip.WriteText(", ")
 		snip.WritePlaceholder(func(b *snippet.Builder) {
 			if c.opts.Placeholders {
 				b.WriteText(secondArg)
 			}
 		})
 	}
 	snip.WriteText(")")

 	var nonSnippet strings.Builder
 	nonSnippet.WriteString("make(" + typeName)
 	if secondArg != "" {
 		nonSnippet.WriteString(", ")
 		nonSnippet.WriteString(secondArg)
 	}
 	nonSnippet.WriteByte(')')

 	c.items = append(c.items, CompletionItem{
 		Label:               nonSnippet.String(),
 		InsertText:          nonSnippet.String(),
 		Score:               matchScore * literalCandidateScore,
 		Kind:                protocol.FunctionCompletion,
 		AdditionalTextEdits: edits,
 		snippet:             snip,
 	})
 }
	// Copyright 2019 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 source

	import (
	"go/ast"
	"go/token"
	"go/types"
	"strings"
	"unicode"

	"golang.org/x/tools/internal/lsp/diff"
	"golang.org/x/tools/internal/lsp/protocol"
	"golang.org/x/tools/internal/lsp/snippet"
	"golang.org/x/tools/internal/span"
	"golang.org/x/tools/internal/telemetry/log"
	)

	// literal generates composite literal, function literal, and make()
	// completion items.
	func (c completer) literal(literalType types.Type, imp importInfo) {
	if c.expectedType.objType == nil {
	return
	}

	// Don't provide literal candidates for variadic function arguments.
	// For example, don't provide "[]interface{}{}" in "fmt.Print(<>)".
	if c.expectedType.variadic {
	return
	}

	// Avoid literal candidates if the expected type is an empty
	// interface. It isn't very useful to suggest a literal candidate of
	// every possible type.
	if isEmptyInterface(c.expectedType.objType) {
	return
	}

	// We handle unnamed literal completions explicitly before searching
	// for candidates. Avoid named-type literal completions for
	// unnamed-type expected type since that results in duplicate
	// candidates. For example, in
	//
	// type mySlice []int
	// var []int = <>
	//
	// don't offer "mySlice{}" since we have already added a candidate
	// of "[]int{}".
	if _, named := literalType.(*types.Named); named {
	if _, named := deref(c.expectedType.objType).(*types.Named); !named {
	return
	}
	}

	// Check if an object of type literalType or *literalType would
	// match our expected type.
	if !c.matchingType(literalType) {
	literalType = types.NewPointer(literalType)

	if !c.matchingType(literalType) {
	return
	}
	}

	ptr, isPointer := literalType.(*types.Pointer)
	if isPointer {
	literalType = ptr.Elem()
	}

	var (
	qf = c.qf
	sel = enclosingSelector(c.path, c.pos)
	)

	// Don't qualify the type name if we are in a selector expression
	// since the package name is already present.
	if sel != nil {
	qf = func(_ *types.Package) string { return "" }
	}

	typeName := types.TypeString(literalType, qf)

	// A type name of "[]int" doesn't work very will with the matcher
	// since "[" isn't a valid identifier prefix. Here we strip off the
	// slice (and array) prefix yielding just "int".
	matchName := typeName
	switch t := literalType.(type) {
	case *types.Slice:
	matchName = types.TypeString(t.Elem(), qf)
	case *types.Array:
	matchName = types.TypeString(t.Elem(), qf)
	}

	addlEdits, err := c.importEdits(imp)
	if err != nil {
	log.Error(c.ctx, "error adding import for literal candidate", err)
	return
	}

	// If prefix matches the type name, client may want a composite literal.
	if score := c.matcher.Score(matchName); score >= 0 {
	if isPointer {
	if sel != nil {
	// If we are in a selector we must place the "&" before the selector.
	// For example, "foo.B<>" must complete to "&foo.Bar{}", not
	// "foo.&Bar{}".
	edits, err := referenceEdit(c.view.Session().Cache().FileSet(), c.mapper, sel)
	if err != nil {
	log.Error(c.ctx, "error making edit for literal pointer completion", err)
	return
	}
	addlEdits = append(addlEdits, edits...)
	} else {
	// Otherwise we can stick the "&" directly before the type name.
	typeName = "&" + typeName
	}
	}

	switch t := literalType.Underlying().(type) {
	case types.Struct, types.Array, types.Slice, types.Map:
	c.compositeLiteral(t, typeName, float64(score), addlEdits)
	case *types.Basic:
	// Add a literal completion for basic types that implement our
	// expected interface (e.g. named string type http.Dir
	// implements http.FileSystem).
	if isInterface(c.expectedType.objType) {
	c.basicLiteral(t, typeName, float64(score), addlEdits)
	}
	}
	}

	// If prefix matches "make", client may want a "make()"
	// invocation. We also include the type name to allow for more
	// flexible fuzzy matching.
	if score := c.matcher.Score("make." + matchName); !isPointer && score >= 0 {
	switch literalType.Underlying().(type) {
	case *types.Slice:
	// The second argument to "make()" for slices is required, so default to "0".
	c.makeCall(typeName, "0", float64(score), addlEdits)
	case types.Map, types.Chan:
	// Maps and channels don't require the second argument, so omit
	// to keep things simple for now.
	c.makeCall(typeName, "", float64(score), addlEdits)
	}
	}

	// If prefix matches "func", client may want a function literal.
	if score := c.matcher.Score("func"); !isPointer && score >= 0 {
	switch t := literalType.Underlying().(type) {
	case *types.Signature:
	c.functionLiteral(t, float64(score))
	}
	}
	}

	// referenceEdit produces text edits that prepend a "&" operator to the
	// specified node.
	func referenceEdit(fset token.FileSet, m protocol.ColumnMapper, node ast.Node) ([]protocol.TextEdit, error) {
	rng := span.Range{
	FileSet: fset,
	Start: node.Pos(),
	End: node.Pos(),
	}
	spn, err := rng.Span()
	if err != nil {
	return nil, err
	}
	return ToProtocolEdits(m, []diff.TextEdit{{
	Span: spn,
	NewText: "&",
	}})
	}

	// literalCandidateScore is the base score for literal candidates.
	// Literal candidates match the expected type so they should be high
	// scoring, but we want them ranked below lexical objects of the
	// correct type, so scale down highScore.
	const literalCandidateScore = highScore / 2

	// functionLiteral adds a function literal completion item for the
	// given signature.
	func (c completer) functionLiteral(sig types.Signature, matchScore float64) {
	snip := &snippet.Builder{}
	snip.WriteText("func(")
	seenParamNames := make(map[string]bool)
	for i := 0; i < sig.Params().Len(); i++ {
	if i > 0 {
	snip.WriteText(", ")
	}

	p := sig.Params().At(i)
	name := p.Name()

	// If the parameter has no name in the signature, we need to try
	// come up with a parameter name.
	if name == "" {
	// Our parameter names are guesses, so they must be placeholders
	// for easy correction. If placeholders are disabled, don't
	// offer the completion.
	if !c.opts.Placeholders {
	return
	}

	// Try abbreviating named types. If the type isn't named, or the
	// abbreviation duplicates a previous name, give up and use
	// "_". The user will have to provide a name for this parameter
	// in order to use it.
	if named, ok := deref(p.Type()).(*types.Named); ok {
	name = abbreviateCamel(named.Obj().Name())
	if seenParamNames[name] {
	name = "_"
	} else {
	seenParamNames[name] = true
	}
	} else {
	name = "_"
	}
	snip.WritePlaceholder(func(b *snippet.Builder) {
	b.WriteText(name)
	})
	} else {
	snip.WriteText(name)
	}

	// If the following param's type is identical to this one, omit
	// this param's type string. For example, emit "i, j int" instead
	// of "i int, j int".
	if i == sig.Params().Len()-1 \|\| !types.Identical(p.Type(), sig.Params().At(i+1).Type()) {
	snip.WriteText(" ")
	typeStr := types.TypeString(p.Type(), c.qf)
	if sig.Variadic() && i == sig.Params().Len()-1 {
	typeStr = strings.Replace(typeStr, "[]", "...", 1)
	}
	snip.WriteText(typeStr)
	}
	}
	snip.WriteText(")")

	results := sig.Results()
	if results.Len() > 0 {
	snip.WriteText(" ")
	}

	resultsNeedParens := results.Len() > 1 \|\|
	results.Len() == 1 && results.At(0).Name() != ""

	if resultsNeedParens {
	snip.WriteText("(")
	}
	for i := 0; i < results.Len(); i++ {
	if i > 0 {
	snip.WriteText(", ")
	}
	r := results.At(i)
	if name := r.Name(); name != "" {
	snip.WriteText(name + " ")
	}
	snip.WriteText(types.TypeString(r.Type(), c.qf))
	}
	if resultsNeedParens {
	snip.WriteText(")")
	}

	snip.WriteText(" {")
	snip.WriteFinalTabstop()
	snip.WriteText("}")

	c.items = append(c.items, CompletionItem{
	Label: "func(...) {}",
	Score: matchScore * literalCandidateScore,
	Kind: protocol.VariableCompletion,
	snippet: snip,
	})
	}

	// abbreviateCamel abbreviates camel case identifiers into
	// abbreviations. For example, "fooBar" is abbreviated "fb".
	func abbreviateCamel(s string) string {
	var (
	b strings.Builder
	useNextUpper bool
	)
	for i, r := range s {
	if i == 0 {
	b.WriteRune(unicode.ToLower(r))
	}

	if unicode.IsUpper(r) {
	if useNextUpper {
	b.WriteRune(unicode.ToLower(r))
	useNextUpper = false
	}
	} else {
	useNextUpper = true
	}
	}

	return b.String()
	}

	// compositeLiteral adds a composite literal completion item for the given typeName.
	func (c *completer) compositeLiteral(T types.Type, typeName string, matchScore float64, edits []protocol.TextEdit) {
	snip := &snippet.Builder{}
	snip.WriteText(typeName + "{")
	// Don't put the tab stop inside the composite literal curlies "{}"
	// for structs that have no fields.
	if strct, ok := T.(*types.Struct); !ok \|\| strct.NumFields() > 0 {
	snip.WriteFinalTabstop()
	}
	snip.WriteText("}")

	nonSnippet := typeName + "{}"

	c.items = append(c.items, CompletionItem{
	Label: nonSnippet,
	InsertText: nonSnippet,
	Score: matchScore * literalCandidateScore,
	Kind: protocol.VariableCompletion,
	AdditionalTextEdits: edits,
	snippet: snip,
	})
	}

	// basicLiteral adds a literal completion item for the given basic
	// type name typeName.
	func (c *completer) basicLiteral(T types.Type, typeName string, matchScore float64, edits []protocol.TextEdit) {
	snip := &snippet.Builder{}
	snip.WriteText(typeName + "(")
	snip.WriteFinalTabstop()
	snip.WriteText(")")

	nonSnippet := typeName + "()"

	c.items = append(c.items, CompletionItem{
	Label: nonSnippet,
	InsertText: nonSnippet,
	Detail: T.String(),
	Score: matchScore * literalCandidateScore,
	Kind: protocol.VariableCompletion,
	AdditionalTextEdits: edits,
	snippet: snip,
	})
	}

	// makeCall adds a completion item for a "make()" call given a specific type.
	func (c *completer) makeCall(typeName string, secondArg string, matchScore float64, edits []protocol.TextEdit) {
	// Keep it simple and don't add any placeholders for optional "make()" arguments.

	snip := &snippet.Builder{}
	snip.WriteText("make(" + typeName)
	if secondArg != "" {
	snip.WriteText(", ")
	snip.WritePlaceholder(func(b *snippet.Builder) {
	if c.opts.Placeholders {
	b.WriteText(secondArg)
	}
	})
	}
	snip.WriteText(")")

	var nonSnippet strings.Builder
	nonSnippet.WriteString("make(" + typeName)
	if secondArg != "" {
	nonSnippet.WriteString(", ")
	nonSnippet.WriteString(secondArg)
	}
	nonSnippet.WriteByte(')')

	c.items = append(c.items, CompletionItem{
	Label: nonSnippet.String(),
	InsertText: nonSnippet.String(),
	Score: matchScore * literalCandidateScore,
	Kind: protocol.FunctionCompletion,
	AdditionalTextEdits: edits,
	snippet: snip,
	})
	}