Partial update

.gitignore

@@ -1 +1,2 @@
 dist/
+.idea/

internal/filesystem/file.go

@@ -1,8 +1,10 @@
 package filesystem
 
 import (
+	"bytes"
 	"path/filepath"
 
+	"github.com/hashicorp/hcl/v2"
 	"github.com/hashicorp/terraform-ls/internal/source"
 	encunicode "golang.org/x/text/encoding/unicode"
 )
@@ -16,8 +18,9 @@ type file struct {
 	content  []byte
 	open     bool
 
-	ls   source.Lines
-	errs bool
+	version int
+	ls      source.Lines
+	errs    bool
 }
 
 func NewFile(fullPath string, content []byte) *file {
@@ -40,6 +43,14 @@ func (f *file) URI() string {
 	return URIFromPath(f.fullPath)
 }
 
+func (f *file) Version() int {
+	return f.version
+}
+
+func (f *file) SetVersion(version int) {
+	f.version = version
+}
+
 func (f *file) Lines() source.Lines {
 	if f.ls == nil {
 		f.ls = source.MakeSourceLines(f.Filename(), f.content)
@@ -52,13 +63,33 @@ func (f *file) Text() []byte {
 }
 
 func (f *file) applyChange(change FileChange) error {
-	newBytes := []byte(change.Text())
-	f.change(newBytes)
+	// if the range is regarded as nil, we regard it as full content change
+	if rangeIsNil(change.Range()) {
+		f.change([]byte(change.Text()))
+		return nil
+	}
+	b := &bytes.Buffer{}
+	b.Grow(len(f.content) + diffLen(change))
+	b.Write(f.content[:change.Range().Start.Byte])
+	b.WriteString(change.Text())
+	b.Write(f.content[change.Range().End.Byte:])
 
+	f.change(b.Bytes())
 	return nil
 }
 
 func (f *file) change(s []byte) {
 	f.content = s
 	f.ls = nil
 }
+
+// HCL column and line indexes start from 1, therefore if the any index
+// contains 0, we assume it is an undefined range
+func rangeIsNil(r hcl.Range) bool {
+	return r.End.Column == 0 && r.End.Line == 0
+}
+
+func diffLen(change FileChange) int {
+	rangeLen := change.Range().End.Byte - change.Range().Start.Byte
+	return len(change.Text()) - rangeLen
+}

internal/filesystem/file_test.go

@@ -18,16 +18,139 @@ func TestFile_ApplyChange_fullUpdate(t *testing.T) {
 	}
 }
 
+func TestFile_ApplyChange_partialUpdate(t *testing.T) {
+	testData := []struct {
+		Name       string
+		Content    string
+		FileChange *fileChange
+		Expect     string
+	}{
+		{
+			Name:    "length grow: 4",
+			Content: "hello world",
+			FileChange: &fileChange{
+				text: "terraform",
+				rng: hcl.Range{
+					Start: hcl.Pos{
+						Line:   1,
+						Column: 7,
+						Byte:   6,
+					},
+					End: hcl.Pos{
+						Line:   1,
+						Column: 12,
+						Byte:   11,
+					},
+				},
+			},
+			Expect: "hello terraform",
+		},
+		{
+			Name:    "length the same",
+			Content: "hello world",
+			FileChange: &fileChange{
+				text: "earth",
+				rng: hcl.Range{
+					Start: hcl.Pos{
+						Line:   1,
+						Column: 7,
+						Byte:   6,
+					},
+					End: hcl.Pos{
+						Line:   1,
+						Column: 12,
+						Byte:   11,
+					},
+				},
+			},
+			Expect: "hello earth",
+		},
+		{
+			Name:    "length grow: -2",
+			Content: "hello world",
+			FileChange: &fileChange{
+				text: "HCL",
+				rng: hcl.Range{
+					Start: hcl.Pos{
+						Line:   1,
+						Column: 7,
+						Byte:   6,
+					},
+					End: hcl.Pos{
+						Line:   1,
+						Column: 12,
+						Byte:   11,
+					},
+				},
+			},
+			Expect: "hello HCL",
+		},
+		{
+			Name:    "add utf-18 character",
+			Content: "hello world",
+			FileChange: &fileChange{
+				text: "𐐀𐐀 ",
+				rng: hcl.Range{
+					Start: hcl.Pos{
+						Line:   1,
+						Column: 7,
+						Byte:   6,
+					},
+					End: hcl.Pos{
+						Line:   1,
+						Column: 7,
+						Byte:   6,
+					},
+				},
+			},
+			Expect: "hello 𐐀𐐀 world",
+		},
+		{
+			Name:    "modify when containing utf-18 character",
+			Content: "hello 𐐀𐐀 world",
+			FileChange: &fileChange{
+				text: "aa𐐀",
+				rng: hcl.Range{
+					Start: hcl.Pos{
+						Line:   1,
+						Column: 9,
+						Byte:   10,
+					},
+					End: hcl.Pos{
+						Line:   1,
+						Column: 11,
+						Byte:   14,
+					},
+				},
+			},
+			Expect: "hello 𐐀aa𐐀 world",
+		},
+	}
+
+	for _, v := range testData {
+		t.Logf("[DEBUG] Testing %q", v.Name)
+
+		f := NewFile("file:///test.tf", []byte(v.Content))
+		err := f.applyChange(v.FileChange)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if string(f.content) != v.Expect {
+			t.Fatalf("expected: %q but actually: %q", v.Expect, string(f.content))
+		}
+	}
+}
+
 type fileChange struct {
 	text string
+	rng  hcl.Range
 }
 
 func (fc *fileChange) Text() string {
 	return fc.text
 }
 
 func (fc *fileChange) Range() hcl.Range {
-	return hcl.Range{
-		// TODO: Implement partial updates
-	}
+	return fc.rng
 }

internal/filesystem/filesystem.go

@@ -39,6 +39,7 @@ func (fs *fsystem) Open(file File) error {
 		f = NewFile(file.FullPath(), file.Text())
 	}
 	f.open = true
+	f.version = file.Version()
 	d.files[file.Filename()] = f
 	return nil
 }
@@ -54,6 +55,7 @@ func (fs *fsystem) Change(fh VersionedFileHandler, changes FileChanges) error {
 	for _, change := range changes {
 		f.applyChange(change)
 	}
+	f.SetVersion(fh.Version())
 	return nil
 }
 

internal/filesystem/filesystem_test.go

@@ -4,15 +4,14 @@ import (
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
-	"github.com/hashicorp/hcl/v2"
 	"github.com/hashicorp/terraform-ls/internal/source"
 )
 
 func TestFilesystem_Change_notOpen(t *testing.T) {
 	fs := NewFilesystem()
 
 	var changes FileChanges
-	changes = append(changes, &testChange{})
+	changes = append(changes, &fileChange{})
 	h := &testHandler{"file:///doesnotexist"}
 
 	err := fs.Change(h, changes)
@@ -41,7 +40,7 @@ func TestFilesystem_Change_closed(t *testing.T) {
 	}
 
 	var changes FileChanges
-	changes = append(changes, &testChange{})
+	changes = append(changes, &fileChange{})
 	err = fs.Change(fh, changes)
 
 	expectedErr := &FileNotOpenErr{fh}
@@ -105,10 +104,10 @@ func TestFilesystem_Change_multipleChanges(t *testing.T) {
 	})
 
 	var changes FileChanges
-	changes = append(changes, &testChange{text: "ahoy"})
-	changes = append(changes, &testChange{text: ""})
-	changes = append(changes, &testChange{text: "quick brown fox jumped over\nthe lazy dog"})
-	changes = append(changes, &testChange{text: "bye"})
+	changes = append(changes, &fileChange{text: "ahoy"})
+	changes = append(changes, &fileChange{text: ""})
+	changes = append(changes, &fileChange{text: "quick brown fox jumped over\nthe lazy dog"})
+	changes = append(changes, &fileChange{text: "bye"})
 
 	err := fs.Change(fh, changes)
 	if err != nil {
@@ -196,17 +195,3 @@ func (fh *testHandler) Filename() string {
 func (fh *testHandler) Version() int {
 	return 0
 }
-
-type testChange struct {
-	text string
-}
-
-func (ch *testChange) Text() string {
-	return ch.text
-}
-
-func (ch *testChange) Range() hcl.Range {
-	return hcl.Range{
-		// TODO: Implement partial updates
-	}
-}

internal/filesystem/types.go

@@ -9,6 +9,7 @@ type File interface {
 	FileHandler
 	Text() []byte
 	Lines() source.Lines
+	Version() int
 }
 
 type FilePosition interface {

internal/lsp/file.go

@@ -14,9 +14,10 @@ type File interface {
 }
 
 type file struct {
-	fh   FileHandler
-	ls   source.Lines
-	text []byte
+	fh      FileHandler
+	ls      source.Lines
+	text    []byte
+	version int
 }
 
 func (f *file) URI() string {
@@ -50,9 +51,14 @@ func (f *file) lines() source.Lines {
 	return f.ls
 }
 
+func (f *file) Version() int {
+	return f.version
+}
+
 func FileFromDocumentItem(doc lsp.TextDocumentItem) *file {
 	return &file{
-		fh:   FileHandler(doc.URI),
-		text: []byte(doc.Text),
+		fh:      FileHandler(doc.URI),
+		text:    []byte(doc.Text),
+		version: doc.Version,
 	}
 }

internal/lsp/file_change.go

@@ -1,8 +1,6 @@
 package lsp
 
 import (
-	"fmt"
-
 	"github.com/hashicorp/hcl/v2"
 	"github.com/hashicorp/terraform-ls/internal/filesystem"
 	"github.com/sourcegraph/go-lsp"
@@ -15,7 +13,15 @@ type fileChange struct {
 
 func FileChange(chEvent lsp.TextDocumentContentChangeEvent, f File) (*fileChange, error) {
 	if chEvent.Range != nil {
-		return nil, fmt.Errorf("Partial updates are not supported (yet)")
+		rng, err := lspRangeToHCL(*chEvent.Range, f)
+		if err != nil {
+			return nil, err
+		}
+
+		return &fileChange{
+			text: chEvent.Text,
+			rng:  *rng,
+		}, nil
 	}
 
 	return &fileChange{
@@ -61,6 +67,24 @@ func hclRangeToLSP(hclRng hcl.Range) lsp.Range {
 	}
 }
 
+func lspRangeToHCL(lspRng lsp.Range, f File) (*hcl.Range, error) {
+	startPos, err := lspPositionToHCL(f.Lines(), lspRng.Start)
+	if err != nil {
+		return nil, err
+	}
+
+	endPos, err := lspPositionToHCL(f.Lines(), lspRng.End)
+	if err != nil {
+		return nil, err
+	}
+
+	return &hcl.Range{
+		Filename: f.Filename(),
+		Start:    startPos,
+		End:      endPos,
+	}, nil
+}
+
 func (fc *fileChange) Text() string {
 	return fc.text
 }