feat: On format, apply edits to single lines instead of replacing the whole file

Otherwise, vscode will jump to the end of the file every time the user saves

Uses https://github.com/hexops/gotextdiff/ which in turn just copies the code used by the golang LSP: https://github.com/golang/tools/tree/master/internal/lsp/diff

Closes #15

Signed-off-by: Julien Duchesne <[email protected]>

Author: julienduchesne

.github/workflows/test.yml

@@ -0,0 +1,14 @@
+name: go test
+on:
+  push:
+    branches:
+      - main
+  pull_request: {}
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-go@v2
+      - run: go test ./...
+      

diff.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"github.com/hexops/gotextdiff/myers"
+	"github.com/hexops/gotextdiff/span"
+	"github.com/jdbaldry/go-language-server-protocol/lsp/protocol"
+)
+
+func getTextEdits(before, after string) []protocol.TextEdit {
+	edits := myers.ComputeEdits(span.URI("any"), before, after)
+
+	var result []protocol.TextEdit
+	for _, edit := range edits {
+		result = append(result, protocol.TextEdit{
+			Range: protocol.Range{
+				Start: protocol.Position{Line: uint32(edit.Span.Start().Line()) - 1, Character: uint32(edit.Span.Start().Column()) - 1},
+				End:   protocol.Position{Line: uint32(edit.Span.End().Line()) - 1, Character: uint32(edit.Span.End().Column()) - 1},
+			},
+			NewText: edit.NewText,
+		})
+	}
+
+	return result
+}

diff_test.go

@@ -0,0 +1,73 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/jdbaldry/go-language-server-protocol/lsp/protocol"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestGetTextEdits(t *testing.T) {
+	testCases := []struct {
+		name          string
+		before, after string
+		expected      []protocol.TextEdit
+	}{
+		{
+			name:   "delete whole file",
+			before: "one\ntwo\nthree",
+			after:  "",
+			expected: []protocol.TextEdit{
+				{
+					Range: protocol.Range{
+						Start: protocol.Position{Line: 0, Character: 0},
+						End:   protocol.Position{Line: 3, Character: 0},
+					},
+					NewText: "",
+				},
+			},
+		},
+		{
+			name:   "add one char (replaces the whole line)",
+			before: "one\ntwo\nthree",
+			after:  "one\ntwoo\nthree",
+			expected: []protocol.TextEdit{
+				{
+					Range: protocol.Range{
+						Start: protocol.Position{Line: 1, Character: 0},
+						End:   protocol.Position{Line: 2, Character: 0},
+					},
+					NewText: "",
+				},
+				{
+					Range: protocol.Range{
+						Start: protocol.Position{Line: 2, Character: 0},
+						End:   protocol.Position{Line: 2, Character: 0},
+					},
+					NewText: "twoo\n",
+				},
+			},
+		},
+		{
+			name:   "delete a line",
+			before: "one\ntwo\nthree",
+			after:  "one\nthree",
+			expected: []protocol.TextEdit{
+				{
+					Range: protocol.Range{
+						Start: protocol.Position{Line: 1, Character: 0},
+						End:   protocol.Position{Line: 2, Character: 0},
+					},
+					NewText: "",
+				},
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			got := getTextEdits(tc.before, tc.after)
+			assert.Equal(t, tc.expected, got)
+		})
+	}
+}

go.mod

@@ -4,5 +4,7 @@ go 1.16
 
 require (
 	github.com/google/go-jsonnet v0.17.0
+	github.com/hexops/gotextdiff v1.0.3
 	github.com/jdbaldry/go-language-server-protocol v0.0.0-20211013214444-3022da0884b2
+	github.com/stretchr/testify v1.4.0
 )

go.sum

@@ -1,25 +1,35 @@
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/fatih/color v1.9.0/go.mod h1:eQcE1qtQxscV5RaZvpXrrb8Drkc3/DdQ+uUYCNjL+zU=
 github.com/google/go-jsonnet v0.17.0 h1:/9NIEfhK1NQRKl3sP2536b2+x5HnZMdql7x3yK/l8JY=
 github.com/google/go-jsonnet v0.17.0/go.mod h1:sOcuej3UW1vpPTZOr8L7RQimqai1a57bt5j22LzGZCw=
+github.com/hexops/gotextdiff v1.0.3 h1:gitA9+qJrrTCsiCl7+kh75nPqQt1cx4ZkudSTLoUqJM=
+github.com/hexops/gotextdiff v1.0.3/go.mod h1:pSWU5MAI3yDq+fZBTazCSJysOMbxWL1BSow5/V2vxeg=
 github.com/jdbaldry/go-language-server-protocol v0.0.0-20211013214444-3022da0884b2 h1:t0A10MAY8Z3eeBIBzlzrPpdjsag6Biuxq8iMCHmdGU8=
 github.com/jdbaldry/go-language-server-protocol v0.0.0-20211013214444-3022da0884b2/go.mod h1:Hp8QDOEcdn4aDZ+DFTda+smIB0b5MvII4Q0Jo0y2VkA=
+github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
+github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/mattn/go-colorable v0.1.4/go.mod h1:U0ppj6V5qS13XJ6of8GYAs25YV2eR4EVcfRqFIhoBtE=
 github.com/mattn/go-isatty v0.0.8/go.mod h1:Iq45c/XA43vh69/j3iqttzPXn0bhXyGjM0Hdxcsrc5s=
 github.com/mattn/go-isatty v0.0.11/go.mod h1:PhnuNfih5lzO57/f3n+odYbM4JtupLOxQOAqxQCu2WE=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/sergi/go-diff v1.1.0 h1:we8PVUC3FE2uYfodKH/nBHMSetSfHDR6scGdBi+erh0=
 github.com/sergi/go-diff v1.1.0/go.mod h1:STckp+ISIX8hZLjrqAeVduY0gWCT9IjLuqbuNXdaHfM=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20191026070338-33540a1f6037/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 h1:YR8cESwS4TdDjEe65xsg0ogRM/Nc3DYOhEAlW+xobZo=
 gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gopkg.in/yaml.v2 v2.2.4 h1:/eiJrUcujPVeJ3xlSWaiNi3uSVmDGBK1pDHUHAnao1I=
 gopkg.in/yaml.v2 v2.2.4/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

server.go

@@ -410,23 +410,8 @@ func (s *server) Formatting(ctx context.Context, params *protocol.DocumentFormat
 		fmt.Fprintln(os.Stderr, err)
 		return nil, err
 	}
-	// TODO(#15): Consider applying individual edits instead of replacing the whole file when formatting.
-	return []protocol.TextEdit{
-		{
-			Range: protocol.Range{
-				Start: protocol.Position{Line: 0, Character: 0},
-				End:   protocol.Position{Line: 0, Character: 0},
-			},
-			NewText: formatted,
-		},
-		{
-			Range: protocol.Range{
-				Start: protocol.Position{Line: 0, Character: 0},
-				End:   protocol.Position{Line: uint32(strings.Count(formatted+doc.item.Text, "\n")), Character: ^uint32(0)},
-			},
-			NewText: "",
-		},
-	}, nil
+
+	return getTextEdits(doc.item.Text, formatted), nil
 }
 
 func (s *server) Hover(context.Context, *protocol.HoverParams) (*protocol.Hover, error) {