gopls/internal/lsp: add code action for conversion between raw and in…

…terpreted string

The code action for conversion will return when the range is string.
When string is raw string, the action is convert back quote string to double quote string.
Otherwise, the action is convert double quote string to back quote

Fixes golang/go#51200

gopls/internal/lsp/code_action.go

@@ -450,6 +450,10 @@ func refactorRewrite(ctx context.Context, snapshot source.Snapshot, pkg source.P
 		})
 	}
 
+	if action, ok := source.ConvertStringLiteral(pgf, fh, rng); ok {
+		actions = append(actions, action)
+	}
+
 	start, end, err := pgf.RangePos(rng)
 	if err != nil {
 		return nil, err

gopls/internal/lsp/source/change_quote.go

@@ -0,0 +1,103 @@
+// Copyright 2023 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"
+	"strconv"
+	"strings"
+
+	"golang.org/x/tools/go/ast/astutil"
+	"golang.org/x/tools/gopls/internal/bug"
+	"golang.org/x/tools/gopls/internal/lsp/protocol"
+	"golang.org/x/tools/gopls/internal/lsp/safetoken"
+	"golang.org/x/tools/internal/diff"
+)
+
+// ConvertStringLiteral reports whether we can convert between raw and interpreted
+// string literals in the [start, end) range
+//
+// Only the following conditions are true, the action in result is valid
+//   - [start, end) is enclosed by a string literal
+//   - if the string is interpreted string, need check whether the convert is allowed
+func ConvertStringLiteral(pgf *ParsedGoFile, fh FileHandle, rng protocol.Range) (protocol.CodeAction, bool) {
+	lit := findStringLiteral(pgf, rng)
+	if lit == nil {
+		return protocol.CodeAction{}, false
+	}
+	str, err := strconv.Unquote(lit.Value)
+	if err != nil {
+		return protocol.CodeAction{}, false
+	}
+
+	interpreted := lit.Value[0] == '"'
+	// interpreted string need check weather the string can be represented as
+	// a raw string, replace \n to allow a multiple line raw string
+	if interpreted && !strconv.CanBackquote(strings.ReplaceAll(str, "\n", "")) {
+		return protocol.CodeAction{}, false
+	}
+
+	var (
+		title   string
+		newText string
+	)
+	if interpreted {
+		title = "Refactor: convert to raw string literal"
+		newText = "`" + str + "`"
+	} else {
+		title = "Refactor: convert to interpreted string literal"
+		newText = strconv.Quote(str)
+	}
+
+	start, end, err := safetoken.Offsets(pgf.Tok, lit.Pos(), lit.End())
+	if err != nil {
+		bug.Reportf("failed to get string literal offset by token.Pos:%v", err)
+		return protocol.CodeAction{}, false
+	}
+	edits := []diff.Edit{{
+		Start: start,
+		End:   end,
+		New:   newText,
+	}}
+	pedits, err := ToProtocolEdits(pgf.Mapper, edits)
+	if err != nil {
+		bug.Reportf("failed to convert diff.Edit to protocol.TextEdit:%v", err)
+		return protocol.CodeAction{}, false
+	}
+
+	return protocol.CodeAction{
+		Title: title,
+		Kind:  protocol.RefactorRewrite,
+		Edit: &protocol.WorkspaceEdit{
+			DocumentChanges: []protocol.DocumentChanges{
+				{
+					TextDocumentEdit: &protocol.TextDocumentEdit{
+						TextDocument: protocol.OptionalVersionedTextDocumentIdentifier{
+							Version:                fh.Version(),
+							TextDocumentIdentifier: protocol.TextDocumentIdentifier{URI: protocol.URIFromSpanURI(fh.URI())},
+						},
+						Edits: pedits,
+					},
+				},
+			},
+		},
+	}, true
+}
+
+// findStringLiteral find the string literal by the given range
+func findStringLiteral(pgf *ParsedGoFile, rng protocol.Range) *ast.BasicLit {
+	start, end, err := pgf.RangePos(rng)
+	if err != nil {
+		bug.Reportf("(file=%v).RangePos(%v) failed: %v", pgf.URI, rng, err)
+		return nil
+	}
+
+	path, _ := astutil.PathEnclosingInterval(pgf.File, start, end)
+	if lit, ok := path[0].(*ast.BasicLit); ok && lit.Kind == token.STRING {
+		return lit
+	}
+	return nil
+}

gopls/internal/regtest/marker/testdata/codeaction/change_quote.txt

@@ -0,0 +1,69 @@
+This test checks the behavior of the 'change quote' code action.
+
+-- flags --
+-ignore_extra_diags
+
+-- go.mod --
+module golang.org/lsptests/changequote
+
+go 1.18
+
+-- a.go --
+package changequote
+
+import (
+	"fmt"
+)
+
+func foo() {
+	var s string
+	s = "hello" //@codeactionedit(`"`, "refactor.rewrite", a1, "Refactor: convert to raw string literal")
+	s = `hello` //@codeactionedit("`", "refactor.rewrite", a2, "Refactor: convert to interpreted string literal")
+	s = "hello\tworld" //@codeactionedit(`"`, "refactor.rewrite", a3, "Refactor: convert to raw string literal")
+	s = `hello	world` //@codeactionedit("`", "refactor.rewrite", a4, "Refactor: convert to interpreted string literal")
+	s = "hello\nworld" //@codeactionedit(`"`, "refactor.rewrite", a5, "Refactor: convert to raw string literal")
+	// add a comment  to avoid affect diff compute
+	s = `hello
+world` //@codeactionedit("`", "refactor.rewrite", a6, "Refactor: convert to interpreted string literal")
+	s = "hello\"world" //@codeactionedit(`"`, "refactor.rewrite", a7, "Refactor: convert to raw string literal")
+	s = `hello"world` //@codeactionedit("`", "refactor.rewrite", a8, "Refactor: convert to interpreted string literal")
+	s = "hello\x1bworld" //@codeactionerr(`"`, "", "refactor.rewrite", re"found 0 CodeActions")
+	s = "hello`world" //@codeactionerr(`"`, "", "refactor.rewrite", re"found 0 CodeActions")
+	s = "hello\x7fworld" //@codeactionerr(`"`, "", "refactor.rewrite", re"found 0 CodeActions")
+	fmt.Println(s)
+}
+
+-- @a1/a.go --
+@@ -9 +9 @@
+-	s = "hello" //@codeactionedit(`"`, "refactor.rewrite", a1, "Refactor: convert to raw string literal")
++	s = `hello` //@codeactionedit(`"`, "refactor.rewrite", a1, "Refactor: convert to raw string literal")
+-- @a2/a.go --
+@@ -10 +10 @@
+-	s = `hello` //@codeactionedit("`", "refactor.rewrite", a2, "Refactor: convert to interpreted string literal")
++	s = "hello" //@codeactionedit("`", "refactor.rewrite", a2, "Refactor: convert to interpreted string literal")
+-- @a3/a.go --
+@@ -11 +11 @@
+-	s = "hello\tworld" //@codeactionedit(`"`, "refactor.rewrite", a3, "Refactor: convert to raw string literal")
++	s = `hello	world` //@codeactionedit(`"`, "refactor.rewrite", a3, "Refactor: convert to raw string literal")
+-- @a4/a.go --
+@@ -12 +12 @@
+-	s = `hello	world` //@codeactionedit("`", "refactor.rewrite", a4, "Refactor: convert to interpreted string literal")
++	s = "hello\tworld" //@codeactionedit("`", "refactor.rewrite", a4, "Refactor: convert to interpreted string literal")
+-- @a5/a.go --
+@@ -13 +13,2 @@
+-	s = "hello\nworld" //@codeactionedit(`"`, "refactor.rewrite", a5, "Refactor: convert to raw string literal")
++	s = `hello
++world` //@codeactionedit(`"`, "refactor.rewrite", a5, "Refactor: convert to raw string literal")
+-- @a6/a.go --
+@@ -15,2 +15 @@
+-	s = `hello
+-world` //@codeactionedit("`", "refactor.rewrite", a6, "Refactor: convert to interpreted string literal")
++	s = "hello\nworld" //@codeactionedit("`", "refactor.rewrite", a6, "Refactor: convert to interpreted string literal")
+-- @a7/a.go --
+@@ -17 +17 @@
+-	s = "hello\"world" //@codeactionedit(`"`, "refactor.rewrite", a7, "Refactor: convert to raw string literal")
++	s = `hello"world` //@codeactionedit(`"`, "refactor.rewrite", a7, "Refactor: convert to raw string literal")
+-- @a8/a.go --
+@@ -18 +18 @@
+-	s = `hello"world` //@codeactionedit("`", "refactor.rewrite", a8, "Refactor: convert to interpreted string literal")
++	s = "hello\"world" //@codeactionedit("`", "refactor.rewrite", a8, "Refactor: convert to interpreted string literal")