gopls/internal/lsp/regtest: add @rename marker tests

This change adds rudimentary support for @rename
markers, which make an LSP 'rename' request and
assert that the expected file changes are obtained.
We also introduce a separate marker, @renameerr,
for expectations of failure.

The treatment both of changed files and of expected errors
should be used by other markers, for consistency.

Also:
- Env.Mapper returns an error.
- add diff.ApplyBytes and compare.Bytes convenience wrappers.
- simplify fake.ApplyEdits by using ApplyProtocolEdits.
- change ApplyProtocolEdits to use []byte.

Change-Id: Ib64b3d8e12c025f01dd0783b4faee94f082b4895
Reviewed-on: https://go-review.googlesource.com/c/tools/+/466144
Run-TryBot: Alan Donovan <adonovan@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

go/analysis/analysistest/analysistest.go

@@ -184,7 +184,7 @@ func RunWithSuggestedFixes(t Testing, dir string, a *analysis.Analyzer, patterns
 					for _, vf := range ar.Files {
 						if vf.Name == sf {
 							found = true
-							out, err := diff.Apply(string(orig), edits)
+							out, err := diff.ApplyBytes(orig, edits)
 							if err != nil {
 								t.Errorf("%s: error applying fixes: %v", file.Name(), err)
 								continue
@@ -194,7 +194,7 @@ func RunWithSuggestedFixes(t Testing, dir string, a *analysis.Analyzer, patterns
 							// between files in the archive. normalize
 							// this to a single newline.
 							want := string(bytes.TrimRight(vf.Data, "\n")) + "\n"
-							formatted, err := format.Source([]byte(out))
+							formatted, err := format.Source(out)
 							if err != nil {
 								t.Errorf("%s: error formatting edited source: %v\n%s", file.Name(), err, out)
 								continue
@@ -218,14 +218,14 @@ func RunWithSuggestedFixes(t Testing, dir string, a *analysis.Analyzer, patterns
 					catchallEdits = append(catchallEdits, edits...)
 				}
 
-				out, err := diff.Apply(string(orig), catchallEdits)
+				out, err := diff.ApplyBytes(orig, catchallEdits)
 				if err != nil {
 					t.Errorf("%s: error applying fixes: %v", file.Name(), err)
 					continue
 				}
 				want := string(ar.Comment)
 
-				formatted, err := format.Source([]byte(out))
+				formatted, err := format.Source(out)
 				if err != nil {
 					t.Errorf("%s: error formatting resulting source: %v\n%s", file.Name(), err, out)
 					continue

go/analysis/internal/checker/checker.go

@@ -424,11 +424,10 @@ func applyFixes(roots []*action) error {
 			return err
 		}
 
-		applied, err := diff.Apply(string(contents), edits)
+		out, err := diff.ApplyBytes(contents, edits)
 		if err != nil {
 			return err
 		}
-		out := []byte(applied)
 
 		// Try to format the file.
 		if formatted, err := format.Source(out); err == nil {

gopls/internal/lsp/cmd/format.go

@@ -9,6 +9,7 @@ import (
 	"flag"
 	"fmt"
 	"io/ioutil"
+	"os"
 
 	"golang.org/x/tools/gopls/internal/lsp/protocol"
 	"golang.org/x/tools/gopls/internal/lsp/source"
@@ -90,7 +91,7 @@ func (c *format) Run(ctx context.Context, args ...string) error {
 		if c.Write {
 			printIt = false
 			if len(edits) > 0 {
-				ioutil.WriteFile(filename, []byte(formatted), 0644)
+				ioutil.WriteFile(filename, formatted, 0644)
 			}
 		}
 		if c.Diff {
@@ -102,7 +103,7 @@ func (c *format) Run(ctx context.Context, args ...string) error {
 			fmt.Print(unified)
 		}
 		if printIt {
-			fmt.Print(formatted)
+			os.Stdout.Write(formatted)
 		}
 	}
 	return nil

gopls/internal/lsp/cmd/imports.go

@@ -9,6 +9,7 @@ import (
 	"flag"
 	"fmt"
 	"io/ioutil"
+	"os"
 
 	"golang.org/x/tools/gopls/internal/lsp/protocol"
 	"golang.org/x/tools/gopls/internal/lsp/source"
@@ -89,7 +90,7 @@ func (t *imports) Run(ctx context.Context, args ...string) error {
 	switch {
 	case t.Write:
 		if len(edits) > 0 {
-			ioutil.WriteFile(filename, []byte(newContent), 0644)
+			ioutil.WriteFile(filename, newContent, 0644)
 		}
 	case t.Diff:
 		unified, err := diff.ToUnified(filename+".orig", filename, string(file.mapper.Content), sedits)
@@ -98,7 +99,7 @@ func (t *imports) Run(ctx context.Context, args ...string) error {
 		}
 		fmt.Print(unified)
 	default:
-		fmt.Print(string(newContent))
+		os.Stdout.Write(newContent)
 	}
 	return nil
 }

gopls/internal/lsp/cmd/rename.go

@@ -108,7 +108,7 @@ func (r *rename) Run(ctx context.Context, args ...string) error {
 					return fmt.Errorf("%v: %v", edits, err)
 				}
 			}
-			ioutil.WriteFile(filename, []byte(newContent), 0644)
+			ioutil.WriteFile(filename, newContent, 0644)
 		case r.Diff:
 			unified, err := diff.ToUnified(filename+".orig", filename, string(cmdFile.mapper.Content), renameEdits)
 			if err != nil {
@@ -119,7 +119,7 @@ func (r *rename) Run(ctx context.Context, args ...string) error {
 			if len(orderedURIs) > 1 {
 				fmt.Printf("%s:\n", filepath.Base(filename))
 			}
-			fmt.Print(string(newContent))
+			os.Stdout.Write(newContent)
 			if changeCount > 1 { // if this wasn't last change, print newline
 				fmt.Println()
 			}

gopls/internal/lsp/cmd/suggested_fix.go

@@ -9,6 +9,7 @@ import (
 	"flag"
 	"fmt"
 	"io/ioutil"
+	"os"
 
 	"golang.org/x/tools/gopls/internal/lsp/protocol"
 	"golang.org/x/tools/gopls/internal/lsp/source"
@@ -151,7 +152,7 @@ func (s *suggestedFix) Run(ctx context.Context, args ...string) error {
 	switch {
 	case s.Write:
 		if len(edits) > 0 {
-			ioutil.WriteFile(filename, []byte(newContent), 0644)
+			ioutil.WriteFile(filename, newContent, 0644)
 		}
 	case s.Diff:
 		diffs, err := diff.ToUnified(filename+".orig", filename, string(file.mapper.Content), sedits)
@@ -160,7 +161,7 @@ func (s *suggestedFix) Run(ctx context.Context, args ...string) error {
 		}
 		fmt.Print(diffs)
 	default:
-		fmt.Print(string(newContent))
+		os.Stdout.Write(newContent)
 	}
 	return nil
 }

gopls/internal/lsp/fake/edit.go

@@ -6,6 +6,7 @@ package fake
 
 import (
 	"golang.org/x/tools/gopls/internal/lsp/protocol"
+	"golang.org/x/tools/gopls/internal/lsp/source"
 	"golang.org/x/tools/internal/diff"
 )
 
@@ -35,25 +36,14 @@ func EditToChangeEvent(e protocol.TextEdit) protocol.TextDocumentContentChangeEv
 // and returns a new slice containing the lines of the patched file.
 // It is a wrapper around diff.Apply; see that function for preconditions.
 func applyEdits(mapper *protocol.Mapper, edits []protocol.TextEdit, windowsLineEndings bool) ([]byte, error) {
-	// Convert fake.Edits to diff.Edits
-	diffEdits := make([]diff.Edit, len(edits))
-	for i, edit := range edits {
-		start, end, err := mapper.RangeOffsets(edit.Range)
-		if err != nil {
-			return nil, err
-		}
-		diffEdits[i] = diff.Edit{
-			Start: start,
-			End:   end,
-			New:   edit.NewText,
-		}
+	diffEdits, err := source.FromProtocolEdits(mapper, edits)
+	if err != nil {
+		return nil, err
 	}
-
-	patchedString, err := diff.Apply(string(mapper.Content), diffEdits)
+	patched, err := diff.ApplyBytes(mapper.Content, diffEdits)
 	if err != nil {
 		return nil, err
 	}
-	patched := []byte(patchedString)
 	if windowsLineEndings {
 		patched = toWindowsLineEndings(patched)
 	}

gopls/internal/lsp/fake/editor.go

@@ -702,17 +702,15 @@ func (e *Editor) BufferText(name string) (string, bool) {
 	return buf.text(), true
 }
 
-// Mapper returns the protocol.Mapper for the given buffer name.
-//
-// If there is no open buffer with that name, it returns nil.
-func (e *Editor) Mapper(name string) *protocol.Mapper {
+// Mapper returns the protocol.Mapper for the given buffer name, if it is open.
+func (e *Editor) Mapper(name string) (*protocol.Mapper, error) {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	buf, ok := e.buffers[name]
 	if !ok {
-		return nil
+		return nil, fmt.Errorf("no mapper for %q", name)
 	}
-	return buf.mapper
+	return buf.mapper, nil
 }
 
 // BufferVersion returns the current version of the buffer corresponding to