Don't reuse removed synthetic program IDs in the same update

packages/typescript/test/async/api.test.ts

@@ -868,6 +868,36 @@ describe("API", { concurrency }, () => {
         assert.deepEqual(await originalProgram.getSourceFileNames(), ["/src/a.ts"]);
     });
 
+    test("snapshot.update removes and creates synthetic programs together", async () => {
+        await using api = spawnAPI({
+            "/src/a.ts": `export const a = 1;`,
+            "/src/b.ts": `export const b = 2;`,
+        });
+        const snapshot = await api.createSnapshot({
+            createPrograms: [{
+                rootFiles: ["/src/a.ts"],
+                compilerOptions: { noLib: true },
+            }],
+        });
+        const removedProgram = snapshot.operation.createdPrograms[0];
+
+        const updated = await snapshot.update({
+            removePrograms: [removedProgram.id],
+            createPrograms: [{
+                rootFiles: ["/src/b.ts"],
+                compilerOptions: { noLib: true },
+            }],
+        });
+        const createdProgram = updated.operation.createdPrograms[0];
+
+        assert.notEqual(createdProgram.id, removedProgram.id);
+        assert.equal(updated.getProgram(removedProgram.id), undefined);
+        assert.deepEqual(updated.getProjects().map(project => project.id), [createdProgram.id]);
+        assert.deepEqual(await createdProgram.getSourceFileNames(), ["/src/b.ts"]);
+        assert.deepEqual(await createdProgram.getSemanticDiagnostics("/src/b.ts"), []);
+        assert.deepEqual(await removedProgram.getSourceFileNames(), ["/src/a.ts"]);
+    });
+
     test("snapshot.update reconfigures module resolution providers", async () => {
         const root = toRootedFilePath("/src/index.ts", undefined);
         const providedA = toRootedFilePath("/a.d.ts", undefined);

packages/typescript/test/sync/api.test.ts

@@ -855,6 +855,36 @@ describe("API", { concurrency }, () => {
         assert.deepEqual(originalProgram.getSourceFileNames(), ["/src/a.ts"]);
     });
 
+    test("snapshot.update removes and creates synthetic programs together", () => {
+        using api = spawnAPI({
+            "/src/a.ts": `export const a = 1;`,
+            "/src/b.ts": `export const b = 2;`,
+        });
+        const snapshot = api.createSnapshot({
+            createPrograms: [{
+                rootFiles: ["/src/a.ts"],
+                compilerOptions: { noLib: true },
+            }],
+        });
+        const removedProgram = snapshot.operation.createdPrograms[0];
+
+        const updated = snapshot.update({
+            removePrograms: [removedProgram.id],
+            createPrograms: [{
+                rootFiles: ["/src/b.ts"],
+                compilerOptions: { noLib: true },
+            }],
+        });
+        const createdProgram = updated.operation.createdPrograms[0];
+
+        assert.notEqual(createdProgram.id, removedProgram.id);
+        assert.equal(updated.getProgram(removedProgram.id), undefined);
+        assert.deepEqual(updated.getProjects().map(project => project.id), [createdProgram.id]);
+        assert.deepEqual(createdProgram.getSourceFileNames(), ["/src/b.ts"]);
+        assert.deepEqual(createdProgram.getSemanticDiagnostics("/src/b.ts"), []);
+        assert.deepEqual(removedProgram.getSourceFileNames(), ["/src/a.ts"]);
+    });
+
     test("snapshot.update reconfigures module resolution providers", () => {
         const root = toRootedFilePath("/src/index.ts", undefined);
         const providedA = toRootedFilePath("/a.d.ts", undefined);

tsc/internal/api/session_apistate_test.go

@@ -285,6 +285,43 @@ func TestGetCurrentLanguageServerSnapshotCreatesAndRemovesPrograms(t *testing.T)
 	assert.Equal(t, len(projectSession.Snapshot().ProjectCollection.SyntheticProjects()), 0)
 }
 
+func TestGetCurrentLanguageServerSnapshotRemovesAndCreatesPrograms(t *testing.T) {
+	t.Parallel()
+
+	const fileName = "/home/projects/p/index.ts"
+	projectSession, _ := projecttestutil.Setup(map[string]any{fileName: `export const value = 1;`})
+	defer projectSession.Close()
+
+	session := NewLSPSession(projectSession, nil)
+	_, err := session.handleGetCurrentLanguageServerSnapshot(context.Background(), &GetCurrentLanguageServerSnapshotParams{
+		Changes: &LanguageServerSnapshotChanges{
+			CreatePrograms: []*CreateSnapshotProgramParams{{
+				RootFiles:       []DocumentIdentifier{{FileName: fileName}},
+				CompilerOptions: core.CompilerOptions{NoLib: core.TSTrue},
+			}},
+		},
+	})
+	assert.NilError(t, err)
+
+	replaced, err := session.handleGetCurrentLanguageServerSnapshot(context.Background(), &GetCurrentLanguageServerSnapshotParams{
+		Changes: &LanguageServerSnapshotChanges{
+			RemovePrograms: []project.SyntheticProjectID{syntheticProjectID(1)},
+			CreatePrograms: []*CreateSnapshotProgramParams{{
+				RootFiles:       []DocumentIdentifier{{FileName: fileName}},
+				CompilerOptions: core.CompilerOptions{NoLib: core.TSTrue},
+			}},
+		},
+	})
+	assert.NilError(t, err)
+	assert.DeepEqual(t, *replaced.Operation.CreatedPrograms, []project.SyntheticProjectID{syntheticProjectID(2)})
+	assert.Equal(t, len(projectSession.Snapshot().ProjectCollection.SyntheticProjects()), 1)
+	assert.Assert(t, !session.createdPrograms.Has(syntheticProjectID(1)))
+	assert.Assert(t, session.createdPrograms.Has(syntheticProjectID(2)))
+
+	session.Close()
+	assert.Equal(t, len(projectSession.Snapshot().ProjectCollection.SyntheticProjects()), 0)
+}
+
 func TestOpenFilePreservesWindowsDriveLetterCase(t *testing.T) {
 	t.Parallel()
 

tsc/internal/api/session_createprogram_test.go

@@ -280,6 +280,48 @@ func TestUpdateSnapshotEnsuresSyntheticProgram(t *testing.T) {
 	assert.Equal(t, ensured.Projects[0].Dirty, false)
 }
 
+func TestUpdateSnapshotRemovesAndCreatesPrograms(t *testing.T) {
+	t.Parallel()
+
+	const (
+		fileA = "/home/projects/p/a.ts"
+		fileB = "/home/projects/p/b.ts"
+	)
+	projectSession, _ := projecttestutil.Setup(map[string]any{
+		fileA: "export const a = 1;",
+		fileB: "export const b = 1;",
+	})
+	defer projectSession.Close()
+	session := NewLSPSession(projectSession, nil)
+	defer session.Close()
+
+	created, err := session.handleCreateSnapshot(context.Background(), &CreateSnapshotParams{
+		CreatePrograms: []*CreateSnapshotProgramParams{{
+			RootFiles:       []DocumentIdentifier{{FileName: fileA}},
+			CompilerOptions: core.CompilerOptions{NoLib: core.TSTrue},
+		}},
+	})
+	assert.NilError(t, err)
+	assert.DeepEqual(t, *created.Operation.CreatedPrograms, []project.SyntheticProjectID{syntheticProjectID(1)})
+
+	updated, err := session.handleUpdateSnapshot(context.Background(), &UpdateSnapshotParams{
+		Snapshot: created.Snapshot,
+		Changes: &CreateSnapshotParams{
+			RemovePrograms: []project.SyntheticProjectID{syntheticProjectID(1)},
+			CreatePrograms: []*CreateSnapshotProgramParams{{
+				RootFiles:       []DocumentIdentifier{{FileName: fileB}},
+				CompilerOptions: core.CompilerOptions{NoLib: core.TSTrue},
+			}},
+		},
+	})
+	assert.NilError(t, err)
+	assert.DeepEqual(t, *updated.Operation.CreatedPrograms, []project.SyntheticProjectID{syntheticProjectID(2)})
+	assert.DeepEqual(t, updated.Changes.RemovedProjects, []project.ID{syntheticProjectID(1).AsID()})
+	assert.Equal(t, len(updated.Projects), 1)
+	assert.Equal(t, updated.Projects[0].Id, syntheticProjectID(2).AsID())
+	assert.DeepEqual(t, updated.Projects[0].ParsedCommandLine.FileNames, []tspath.RootedFilePath{fileB})
+}
+
 func TestCreateProgramReportsNonCompositeProjectReference(t *testing.T) {
 	t.Parallel()
 

tsc/internal/project/projectcollectionbuilder.go

@@ -388,6 +388,9 @@ func (b *ProjectCollectionBuilder) HandleAPIRequest(apiRequest *APISnapshotReque
 func (b *ProjectCollectionBuilder) nextSyntheticProjectID() SyntheticProjectID {
 	for id := 1; ; id++ {
 		projectID := NewSyntheticProjectID(id)
+		if _, ok := b.base.syntheticProjects[projectID]; ok {
+			continue
+		}
 		if _, ok := b.syntheticProjects.Load(projectID); !ok {
 			return projectID
 		}

tsc/internal/project/snapshot_test.go

@@ -122,6 +122,72 @@ func TestSnapshot(t *testing.T) {
 		assert.Equal(t, len(removedSnapshot.ProjectCollection.SyntheticProjects()), 1)
 	})
 
+	t.Run("removes and creates synthetic programs in one update", func(t *testing.T) {
+		t.Parallel()
+		session := setup(map[string]any{
+			"/a.ts": "export const a = 1;",
+			"/b.ts": "export const b = 1;",
+		})
+		defer session.Close()
+
+		ctx := context.Background()
+		options := &core.CompilerOptions{NoLib: core.TSTrue}
+		createdSnapshot, err := session.CloneSnapshot(
+			ctx,
+			session.Snapshot(),
+			FileChangeSummary{},
+			&APISnapshotRequest{CreatePrograms: []*APICreateProgramRequest{{
+				RootFileNames:   []tspath.RootedFilePath{"/a.ts"},
+				CompilerOptions: options,
+			}}},
+		)
+		assert.NilError(t, err)
+		defer createdSnapshot.Deref()
+		firstProject := createdSnapshot.CreatedPrograms()[0]
+		firstProgramID, ok := firstProject.ID().Synthetic()
+		assert.Assert(t, ok)
+
+		replacedSnapshot, err := session.CloneSnapshot(
+			ctx,
+			createdSnapshot,
+			FileChangeSummary{},
+			&APISnapshotRequest{
+				RemovePrograms: collections.NewSetFromItems(firstProgramID),
+				CreatePrograms: []*APICreateProgramRequest{{
+					RootFileNames:   []tspath.RootedFilePath{"/b.ts"},
+					CompilerOptions: options,
+				}},
+			},
+		)
+		assert.NilError(t, err)
+		defer replacedSnapshot.Deref()
+
+		createdPrograms := replacedSnapshot.CreatedPrograms()
+		assert.Equal(t, len(createdPrograms), 1)
+		secondProject := createdPrograms[0]
+		assert.Assert(t, secondProject.ID() != firstProject.ID())
+		assert.DeepEqual(t, secondProject.CommandLine.FileNames(), []tspath.RootedFilePath{"/b.ts"})
+		assert.Assert(t, secondProject.GetProgram().GetSourceFile("/b.ts") != nil)
+		assert.Assert(t, replacedSnapshot.ProjectCollection.GetProject(firstProject.ID()) == nil)
+		assert.Equal(t, replacedSnapshot.ProjectCollection.GetProject(secondProject.ID()), secondProject)
+		assert.Equal(t, len(replacedSnapshot.ProjectCollection.SyntheticProjects()), 1)
+		assert.Equal(t, createdSnapshot.ProjectCollection.GetProject(firstProject.ID()), firstProject)
+
+		reusedSnapshot, err := session.CloneSnapshot(
+			ctx,
+			replacedSnapshot,
+			FileChangeSummary{},
+			&APISnapshotRequest{CreatePrograms: []*APICreateProgramRequest{{
+				RootFileNames:   []tspath.RootedFilePath{"/a.ts"},
+				CompilerOptions: options,
+			}}},
+		)
+		assert.NilError(t, err)
+		defer reusedSnapshot.Deref()
+		assert.Equal(t, reusedSnapshot.CreatedPrograms()[0].ID(), firstProject.ID())
+		assert.Equal(t, len(reusedSnapshot.ProjectCollection.SyntheticProjects()), 2)
+	})
+
 	t.Run("failed API update is not adopted", func(t *testing.T) {
 		t.Parallel()
 		session := setup(map[string]any{