New flag assumeChangesAffectShape for incremental and watch scenario

src/compiler/builderState.ts

@@ -243,7 +243,8 @@ namespace ts {
                 referencedMap,
                 exportedModulesMap,
                 hasCalledUpdateShapeSignature,
-                useFileVersionAsSignature: !disableUseFileVersionAsSignature && !useOldState
+                useFileVersionAsSignature: (!disableUseFileVersionAsSignature && !useOldState) ||
+                    !!newProgram.getCompilerOptions().assumeChangesAffectShape,
             };
         }
 

src/compiler/commandLineParser.ts

@@ -272,6 +272,12 @@ namespace ts {
             category: Diagnostics.Advanced_Options,
             description: Diagnostics.Have_recompiles_in_incremental_and_watch_assume_that_changes_within_a_file_will_only_affect_files_directly_depending_on_it
         },
+        {
+            name: "assumeChangesAffectShape",
+            type: "boolean",
+            category: Diagnostics.Advanced_Options,
+            description: Diagnostics.Have_recompiles_in_incremental_and_watch_assume_that_any_change_to_file_can_affect_its_shape_resulting_in_affecting_it_s_dependecies
+        },
         {
             name: "locale",
             type: "string",

src/compiler/diagnosticMessages.json

@@ -5061,6 +5061,10 @@
         "category": "Message",
         "code": 6388
     },
+    "Have recompiles in '--incremental' and '--watch' assume that any change to file can affect its shape resulting in affecting it's dependecies.": {
+        "category": "Message",
+        "code": 6389
+    },
 
     "The expected type comes from property '{0}' which is declared here on type '{1}'": {
         "category": "Message",

src/compiler/types.ts

@@ -5965,6 +5965,7 @@ namespace ts {
         noImplicitUseStrict?: boolean;
         noPropertyAccessFromIndexSignature?: boolean;
         assumeChangesOnlyAffectDirectDependencies?: boolean;
+        assumeChangesAffectShape?: boolean;
         noLib?: boolean;
         noResolve?: boolean;
         noUncheckedIndexedAccess?: boolean;

src/testRunner/unittests/tsc/incremental.ts

@@ -293,6 +293,37 @@ const a: string = 10;`, "utf-8"),
             baselinePrograms: true,
         });
 
+        verifyTscSerializedIncrementalEdits({
+            scenario: "incremental",
+            subScenario: "assumeChangesAffectShape",
+            fs: () => loadProjectFromFiles({
+                "/src/project/main.ts": `import { foo } from "./module";foo();`,
+                "/src/project/module.ts": `export function foo(): string { return "hello"; }`,
+                "/src/project/extraFile.ts": "export const extra = 10;",
+                "/src/project/tsconfig.json": JSON.stringify({
+                    compilerOptions: { assumeChangesAffectShape: true }
+                })
+            }),
+            commandLineArgs: ["--incremental", "--p", "src/project"],
+            incrementalScenarios: [
+                {
+                    subScenario: "Local edit to module",
+                    modifyFs: fs => replaceText(fs, "/src/project/module.ts", "hello", "hello world"),
+                    buildKind: BuildKind.IncrementalDtsUnchanged
+                },
+                {
+                    subScenario: "Local edit to module again",
+                    modifyFs: fs => replaceText(fs, "/src/project/module.ts", "hello", "hello world"),
+                    buildKind: BuildKind.IncrementalDtsUnchanged
+                },
+                {
+                    subScenario: "Api change edit to module",
+                    modifyFs: fs => prependText(fs, "/src/project/module.ts", "export const x = 10;"),
+                    buildKind: BuildKind.IncrementalDtsUnchanged
+                },
+            ]
+        });
+
         describe("when synthesized imports are added to files", () => {
             function getJsxLibraryContent() {
                 return `

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -2861,6 +2861,7 @@ declare namespace ts {
         noImplicitUseStrict?: boolean;
         noPropertyAccessFromIndexSignature?: boolean;
         assumeChangesOnlyAffectDirectDependencies?: boolean;
+        assumeChangesAffectShape?: boolean;
         noLib?: boolean;
         noResolve?: boolean;
         noUncheckedIndexedAccess?: boolean;

tests/baselines/reference/api/typescript.d.ts

@@ -2861,6 +2861,7 @@ declare namespace ts {
         noImplicitUseStrict?: boolean;
         noPropertyAccessFromIndexSignature?: boolean;
         assumeChangesOnlyAffectDirectDependencies?: boolean;
+        assumeChangesAffectShape?: boolean;
         noLib?: boolean;
         noResolve?: boolean;
         noUncheckedIndexedAccess?: boolean;

tests/baselines/reference/showConfig/Shows tsconfig for single option/assumeChangesAffectShape/tsconfig.json

@@ -0,0 +1,5 @@
+{
+    "compilerOptions": {
+        "assumeChangesAffectShape": true
+    }
+}