Preserve checking globals before declaration signature generation

Incremental checking must not lose a missing-global error merely because
signature generation discovers it first. Retain each affected file’s
checking diagnostics before computing its declaration shape, without
collecting incidental emit-only globals or checking emit-only builds.

Author: jakebailey

tsc/internal/compiler/program.go

@@ -826,10 +826,16 @@ func (p *Program) GetSemanticDiagnostics(ctx context.Context, sourceFile *ast.So
 // GetSemanticDiagnosticsForIncremental includes newly discovered globals in each
 // file's cached diagnostics and leaves noEmit filtering to the builder.
 func (p *Program) GetSemanticDiagnosticsForIncremental(ctx context.Context, sourceFiles []*ast.SourceFile) map[*ast.SourceFile][]*ast.Diagnostic {
-	allDiags := p.collectCheckerDiagnosticsFromFiles(ctx, sourceFiles, func(ctx context.Context, c *checker.Checker, file *ast.SourceFile) []*ast.Diagnostic {
+	collect := func(ctx context.Context, c *checker.Checker, file *ast.SourceFile) []*ast.Diagnostic {
 		return p.getBindAndCheckDiagnosticsWithChecker(ctx, c, file, true /*includeDeferredGlobals*/)
-	})
+	}
 	result := make(map[*ast.SourceFile][]*ast.Diagnostic, len(sourceFiles))
+	if len(sourceFiles) == 1 {
+		file := sourceFiles[0]
+		result[file] = p.collectCheckerDiagnostics(ctx, file, collect)
+		return result
+	}
+	allDiags := p.collectCheckerDiagnosticsFromFiles(ctx, sourceFiles, collect)
 	for i, diags := range allDiags {
 		result[sourceFiles[i]] = filterAndSortDiagnostics(diags)
 	}

tsc/internal/execute/incremental/affectedfileshandler.go

@@ -22,14 +22,16 @@ func (c dtsMayChange) addFileToAffectedFilesPendingEmit(filePath tspath.PathKey,
 }
 
 type updatedSignature struct {
-	mu        sync.Mutex
-	signature string
-	kind      SignatureUpdateKind
+	mu                  sync.Mutex
+	signature           string
+	kind                SignatureUpdateKind
+	semanticDiagnostics *DiagnosticsOrBuildInfoDiagnosticsWithFileName
 }
 
 type affectedFilesHandler struct {
 	ctx                                    context.Context
 	program                                *Program
+	collectSemanticDiagnostics             bool
 	hasAllFilesExcludingDefaultLibraryFile atomic.Bool
 	updatedSignatures                      collections.SyncMap[tspath.PathKey, *updatedSignature]
 	dtsMayChange                           []dtsMayChange
@@ -101,6 +103,13 @@ func (h *affectedFilesHandler) updateShapeSignature(file *ast.SourceFile, useFil
 	// JSON files have no declaration output from which to compute a shape
 	// signature, so use the file version to conservatively invalidate dependents.
 	if !file.IsDeclarationFile && !ast.IsJsonSourceFile(file) && !useFileVersionAsSignature {
+		if h.collectSemanticDiagnostics && !h.program.snapshot.options.NoCheck.IsTrue() {
+			// Signature generation can discover globals before checking does. Keep the
+			// checking diagnostics first, without retaining incidental emit-only errors.
+			update.semanticDiagnostics = &DiagnosticsOrBuildInfoDiagnosticsWithFileName{
+				diagnostics: h.program.program.GetSemanticDiagnosticsForIncremental(h.ctx, core.SingleElementSlice(file))[file],
+			}
+		}
 		update.signature = h.computeDtsSignature(file)
 	}
 	// Default is to use file version as signature
@@ -347,6 +356,12 @@ func (h *affectedFilesHandler) updateSnapshot() {
 		h.program.snapshot.semanticDiagnosticsPerFile.Delete(file)
 		return true
 	})
+	h.updatedSignatures.Range(func(filePath tspath.PathKey, update *updatedSignature) bool {
+		if update.semanticDiagnostics != nil && h.filesToRemoveDiagnostics.Has(filePath) {
+			h.program.snapshot.semanticDiagnosticsPerFile.Store(filePath, update.semanticDiagnostics)
+		}
+		return true
+	})
 	for _, change := range h.dtsMayChange {
 		for filePath, emitKind := range change {
 			h.program.snapshot.addFileToAffectedFilesPendingEmit(filePath, emitKind)
@@ -356,12 +371,12 @@ func (h *affectedFilesHandler) updateSnapshot() {
 	h.program.snapshot.buildInfoEmitPending.Store(true)
 }
 
-func collectAllAffectedFiles(ctx context.Context, program *Program) {
+func collectAllAffectedFiles(ctx context.Context, program *Program, collectSemanticDiagnostics bool) {
 	if program.snapshot.changedFilesSet.Size() == 0 {
 		return
 	}
 
-	handler := affectedFilesHandler{ctx: ctx, program: program}
+	handler := affectedFilesHandler{ctx: ctx, program: program, collectSemanticDiagnostics: collectSemanticDiagnostics}
 	wg := core.NewWorkGroup(handler.program.program.SingleThreaded())
 	var result collections.SyncSet[*ast.SourceFile]
 	program.snapshot.changedFilesSet.Range(func(file tspath.PathKey) bool {

tsc/internal/execute/incremental/emitfileshandler.go

@@ -116,7 +116,7 @@ func (h *emitFilesHandler) emitBuildInfo(options compiler.EmitOptions, result *c
 
 func (h *emitFilesHandler) emitFilesIncremental(options compiler.EmitOptions) []*compiler.EmitResult {
 	// Get all affected files
-	collectAllAffectedFiles(h.ctx, h.program)
+	collectAllAffectedFiles(h.ctx, h.program, false /*collectSemanticDiagnostics*/)
 	if h.ctx.Err() != nil {
 		return nil
 	}

tsc/internal/execute/incremental/program.go

@@ -275,13 +275,15 @@ func (p *Program) Emit(ctx context.Context, options compiler.EmitOptions) *compi
 func (p *Program) collectSemanticDiagnosticsOfAffectedFiles(ctx context.Context, file *ast.SourceFile) {
 	if p.snapshot.canUseIncrementalState() {
 		// Get all affected files
-		collectAllAffectedFiles(ctx, p)
+		collectAllAffectedFiles(ctx, p, true /*collectSemanticDiagnostics*/)
 		if ctx.Err() != nil {
 			return
 		}
-
 		if p.snapshot.semanticDiagnosticsPerFile.Size() == len(p.program.GetSourceFiles()) {
-			// If we have all the files,
+			if p.snapshot.checkPending && !p.snapshot.options.NoCheck.IsTrue() {
+				p.snapshot.checkPending = false
+				p.snapshot.buildInfoEmitPending.Store(true)
+			}
 			return
 		}
 	}

tsc/internal/execute/tsctests/tsc_test.go

@@ -2326,12 +2326,10 @@ func TestTscIncremental(t *testing.T) {
 					edit: func(sys *TestSys) {
 						sys.appendFile("/home/src/workspaces/project/repro.ts", "\n// comment-only edit\n")
 					},
-					expectedDiff: "Like Strada, signature generation produces the missing-global diagnostic before semantic checking, so it is excluded from the file's semantic diagnostics.",
 				},
 				{
-					caption:      "no change",
-					edit:         noChange.edit,
-					expectedDiff: "Like Strada, the cached semantic diagnostics do not include the missing-global diagnostic produced during signature generation.",
+					caption: "no change",
+					edit:    noChange.edit,
 				},
 				{
 					caption: "delete build info to restore the semantic diagnostic",
@@ -2394,12 +2392,10 @@ func TestTscIncremental(t *testing.T) {
 					edit: func(sys *TestSys) {
 						sys.appendFile("/home/src/workspaces/project/repro.ts", "\n// comment-only edit\n")
 					},
-					expectedDiff: "Signature generation produces the missing-global diagnostic before semantic checking, so the build loses it.",
 				},
 				{
-					caption:      "no change",
-					edit:         noChange.edit,
-					expectedDiff: "The cached semantic diagnostics do not include the missing-global diagnostic produced during signature generation.",
+					caption: "no change",
+					edit:    noChange.edit,
 				},
 				newTscEdit("remove the generator", func(sys *TestSys) {
 					sys.writeFileNoError("/home/src/workspaces/project/repro.ts", `export const value = 1;`)
@@ -2548,6 +2544,44 @@ func TestTscIncremental(t *testing.T) {
 		},
 	}
 
+	for _, checkers := range []int{1, 2} {
+		for _, build := range []bool{false, true} {
+			args := []string{}
+			if build {
+				args = []string{"--build"}
+			}
+			test := &tscInput{
+				subScenario: fmt.Sprintf("global diagnostics with declaration emit checkers %d build %t", checkers, build),
+				files: FileMap{
+					"/home/src/workspaces/project/tsconfig.json": fmt.Sprintf(`{"compilerOptions": {"declaration": true, "incremental": true, "checkers": %d}}`, checkers),
+					"/home/src/workspaces/project/generator.ts":  `export function* values() { yield 1; }`,
+					"/home/src/workspaces/project/index.ts":      `import { values } from "./generator"; export const get = values;`,
+				},
+				commandLineArgs: args,
+				edits: []*tscEdit{
+					newTscEdit("edit both modules without changing their types", func(sys *TestSys) {
+						sys.appendFile("/home/src/workspaces/project/generator.ts", "\n// generator comment\n")
+						sys.appendFile("/home/src/workspaces/project/index.ts", "\n// consumer comment\n")
+					}),
+					noChange,
+					newTscEdit("remove the generator", func(sys *TestSys) {
+						sys.writeFileNoError("/home/src/workspaces/project/generator.ts", `export function values() { return 1; }`)
+					}),
+					noChange,
+					newTscEdit("restore the generator", func(sys *TestSys) {
+						sys.writeFileNoError("/home/src/workspaces/project/generator.ts", `export function* values() { yield 2; }`)
+					}),
+					noChange,
+				},
+			}
+			watchTest := *test
+			watchTest.subScenario += " watch"
+			watchTest.commandLineArgs = append(args, "--watch")
+			watchTest.edits = core.Filter(test.edits, func(edit *tscEdit) bool { return edit != noChange })
+			testCases = append(testCases, test, &watchTest)
+		}
+	}
+
 	for _, test := range testCases {
 		test.run(t, "incremental")
 	}

tsc/testdata/baselines/reference/tsbuild/incremental/global-diagnostics-survive-build-signature-generation.js

@@ -191,10 +191,14 @@ export function* values() { yield 1; }
 
 
 tsgo --build
-ExitStatus:: Success
+ExitStatus:: DiagnosticsPresent_OutputsGenerated
 Output::
+error TS2318: Cannot find global type 'IterableIterator'.
+
+Found 1 error.
+
 //// [/home/src/workspaces/project/tsconfig.tsbuildinfo] *modified* 
-{"version":"FakeTSVersion","errors":true,"root":[2],"fileNames":["lib.es2026.full.d.ts","./repro.ts"],"fileInfos":[{"version":"8859c12c614ce56ba9a18e58384a198f-/// <reference no-default-lib=\"true\"/>\ninterface Boolean {}\ninterface Function {}\ninterface CallableFunction {}\ninterface NewableFunction {}\ninterface IArguments {}\ninterface Number { toExponential: any; }\ninterface Object {}\ninterface RegExp {}\ninterface String { charAt: any; }\ninterface Array<T> { length: number; [n: number]: T; }\ninterface ReadonlyArray<T> {}\ninterface SymbolConstructor {\n    (desc?: string | number): symbol;\n    for(name: string): symbol;\n    readonly toStringTag: symbol;\n}\ndeclare var Symbol: SymbolConstructor;\ninterface Symbol {\n    readonly [Symbol.toStringTag]: string;\n}\ndeclare const console: { log(msg: any): void; };","affectsGlobalScope":true,"impliedNodeFormat":1},{"version":"303d5119b8941b887ef975780b83caec-export function* values() { yield 1; }\n// comment-only edit\n","signature":"b9f7a0d32d9887fdd864bf1c0dcd3591-export declare function values(): {};\n","impliedNodeFormat":1}],"affectedFilesPendingEmit":[2]}
+{"version":"FakeTSVersion","errors":true,"root":[2],"fileNames":["lib.es2026.full.d.ts","./repro.ts"],"fileInfos":[{"version":"8859c12c614ce56ba9a18e58384a198f-/// <reference no-default-lib=\"true\"/>\ninterface Boolean {}\ninterface Function {}\ninterface CallableFunction {}\ninterface NewableFunction {}\ninterface IArguments {}\ninterface Number { toExponential: any; }\ninterface Object {}\ninterface RegExp {}\ninterface String { charAt: any; }\ninterface Array<T> { length: number; [n: number]: T; }\ninterface ReadonlyArray<T> {}\ninterface SymbolConstructor {\n    (desc?: string | number): symbol;\n    for(name: string): symbol;\n    readonly toStringTag: symbol;\n}\ndeclare var Symbol: SymbolConstructor;\ninterface Symbol {\n    readonly [Symbol.toStringTag]: string;\n}\ndeclare const console: { log(msg: any): void; };","affectsGlobalScope":true,"impliedNodeFormat":1},{"version":"303d5119b8941b887ef975780b83caec-export function* values() { yield 1; }\n// comment-only edit\n","signature":"b9f7a0d32d9887fdd864bf1c0dcd3591-export declare function values(): {};\n","impliedNodeFormat":1}],"semanticDiagnosticsPerFile":[[2,[{"noFile":true,"code":2318,"category":1,"messageKey":"Cannot_find_global_type_0_2318","messageArgs":["IterableIterator"]}]]],"affectedFilesPendingEmit":[2]}
 //// [/home/src/workspaces/project/tsconfig.tsbuildinfo.readable.baseline.txt] *modified* 
 {
   "version": "FakeTSVersion",
@@ -236,14 +240,30 @@ Output::
       }
     }
   ],
+  "semanticDiagnosticsPerFile": [
+    [
+      "./repro.ts",
+      [
+        {
+          "noFile": true,
+          "code": 2318,
+          "category": 1,
+          "messageKey": "Cannot_find_global_type_0_2318",
+          "messageArgs": [
+            "IterableIterator"
+          ]
+        }
+      ]
+    ]
+  ],
   "affectedFilesPendingEmit": [
     [
       "./repro.ts",
       "Js",
       2
     ]
   ],
-  "size": 1136
+  "size": 1295
 }
 
 tsconfig.json::
@@ -253,22 +273,17 @@ Signatures::
 (computed .d.ts) /home/src/workspaces/project/repro.ts
 
 
-Diff:: Signature generation produces the missing-global diagnostic before semantic checking, so the build loses it.
---- nonIncremental.output.txt
-+++ incremental.output.txt
-@@ -1,4 +0,0 @@
--error TS2318: Cannot find global type 'IterableIterator'.
--
--Found 1 error.
--
-
 Edit [2]:: no change
 
 tsgo --build
-ExitStatus:: Success
+ExitStatus:: DiagnosticsPresent_OutputsGenerated
 Output::
+error TS2318: Cannot find global type 'IterableIterator'.
+
+Found 1 error.
+
 //// [/home/src/workspaces/project/tsconfig.tsbuildinfo] *modified* 
-{"version":"FakeTSVersion","root":[2],"fileNames":["lib.es2026.full.d.ts","./repro.ts"],"fileInfos":[{"version":"8859c12c614ce56ba9a18e58384a198f-/// <reference no-default-lib=\"true\"/>\ninterface Boolean {}\ninterface Function {}\ninterface CallableFunction {}\ninterface NewableFunction {}\ninterface IArguments {}\ninterface Number { toExponential: any; }\ninterface Object {}\ninterface RegExp {}\ninterface String { charAt: any; }\ninterface Array<T> { length: number; [n: number]: T; }\ninterface ReadonlyArray<T> {}\ninterface SymbolConstructor {\n    (desc?: string | number): symbol;\n    for(name: string): symbol;\n    readonly toStringTag: symbol;\n}\ndeclare var Symbol: SymbolConstructor;\ninterface Symbol {\n    readonly [Symbol.toStringTag]: string;\n}\ndeclare const console: { log(msg: any): void; };","affectsGlobalScope":true,"impliedNodeFormat":1},{"version":"303d5119b8941b887ef975780b83caec-export function* values() { yield 1; }\n// comment-only edit\n","signature":"b9f7a0d32d9887fdd864bf1c0dcd3591-export declare function values(): {};\n","impliedNodeFormat":1}],"affectedFilesPendingEmit":[2]}
+{"version":"FakeTSVersion","root":[2],"fileNames":["lib.es2026.full.d.ts","./repro.ts"],"fileInfos":[{"version":"8859c12c614ce56ba9a18e58384a198f-/// <reference no-default-lib=\"true\"/>\ninterface Boolean {}\ninterface Function {}\ninterface CallableFunction {}\ninterface NewableFunction {}\ninterface IArguments {}\ninterface Number { toExponential: any; }\ninterface Object {}\ninterface RegExp {}\ninterface String { charAt: any; }\ninterface Array<T> { length: number; [n: number]: T; }\ninterface ReadonlyArray<T> {}\ninterface SymbolConstructor {\n    (desc?: string | number): symbol;\n    for(name: string): symbol;\n    readonly toStringTag: symbol;\n}\ndeclare var Symbol: SymbolConstructor;\ninterface Symbol {\n    readonly [Symbol.toStringTag]: string;\n}\ndeclare const console: { log(msg: any): void; };","affectsGlobalScope":true,"impliedNodeFormat":1},{"version":"303d5119b8941b887ef975780b83caec-export function* values() { yield 1; }\n// comment-only edit\n","signature":"b9f7a0d32d9887fdd864bf1c0dcd3591-export declare function values(): {};\n","impliedNodeFormat":1}],"semanticDiagnosticsPerFile":[[2,[{"noFile":true,"code":2318,"category":1,"messageKey":"Cannot_find_global_type_0_2318","messageArgs":["IterableIterator"]}]]],"affectedFilesPendingEmit":[2]}
 //// [/home/src/workspaces/project/tsconfig.tsbuildinfo.readable.baseline.txt] *modified* 
 {
   "version": "FakeTSVersion",
@@ -309,30 +324,37 @@ Output::
       }
     }
   ],
+  "semanticDiagnosticsPerFile": [
+    [
+      "./repro.ts",
+      [
+        {
+          "noFile": true,
+          "code": 2318,
+          "category": 1,
+          "messageKey": "Cannot_find_global_type_0_2318",
+          "messageArgs": [
+            "IterableIterator"
+          ]
+        }
+      ]
+    ]
+  ],
   "affectedFilesPendingEmit": [
     [
       "./repro.ts",
       "Js",
       2
     ]
   ],
-  "size": 1122
+  "size": 1281
 }
 
 tsconfig.json::
 SemanticDiagnostics::
 Signatures::
 
 
-Diff:: The cached semantic diagnostics do not include the missing-global diagnostic produced during signature generation.
---- nonIncremental.output.txt
-+++ incremental.output.txt
-@@ -1,4 +0,0 @@
--error TS2318: Cannot find global type 'IterableIterator'.
--
--Found 1 error.
--
-
 Edit [3]:: remove the generator
 //// [/home/src/workspaces/project/repro.ts] *modified* 
 export const value = 1;