Add assumeChangesOnlyAffectDirectDependencies as a option to skip checking and generating .d.ts files for files indirectly importing affected file

src/compiler/builder.ts

@@ -433,7 +433,9 @@ namespace ts {
             return;
         }
 
-        forEachReferencingModulesOfExportOfAffectedFile(state, affectedFile, (state, path) => handleDtsMayChangeOf(state, path, cancellationToken, computeHash));
+        if (!state.compilerOptions.assumeChangesOnlyAffectDirectDependencies) {
+            forEachReferencingModulesOfExportOfAffectedFile(state, affectedFile, (state, path) => handleDtsMayChangeOf(state, path, cancellationToken, computeHash));
+        }
     }
 
     /**

src/compiler/commandLineParser.ts

@@ -201,6 +201,14 @@ namespace ts {
             description: Diagnostics.Enable_incremental_compilation,
             transpileOptionValue: undefined
         },
+        {
+            name: "assumeChangesOnlyAffectDirectDependencies",
+            type: "boolean",
+            affectsSemanticDiagnostics: true,
+            affectsEmit: true,
+            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: "locale",
             type: "string",

src/compiler/diagnosticMessages.json

@@ -4366,6 +4366,10 @@
         "category": "Message",
         "code": 6383
     },
+    "Have recompiles in '--incremental' and '--watch' assume that changes within a file will only affect files directly depending on it.": {
+        "category": "Message",
+        "code": 6384
+    },
 
     "The expected type comes from property '{0}' which is declared here on type '{1}'": {
         "category": "Message",

src/compiler/tsbuildPublic.ts

@@ -16,6 +16,7 @@ namespace ts {
         /*@internal*/ listFiles?: boolean;
         /*@internal*/ pretty?: boolean;
         incremental?: boolean;
+        assumeChangesOnlyAffectDirectDependencies?: boolean;
 
         traceResolution?: boolean;
         /* @internal */ diagnostics?: boolean;

src/compiler/types.ts

@@ -5070,6 +5070,7 @@ namespace ts {
         noUnusedLocals?: boolean;
         noUnusedParameters?: boolean;
         noImplicitUseStrict?: boolean;
+        assumeChangesOnlyAffectDirectDependencies?: boolean;
         noLib?: boolean;
         noResolve?: boolean;
         out?: string;

src/testRunner/unittests/tscWatch/emitAndErrorUpdates.ts

@@ -66,6 +66,18 @@ namespace ts.tscWatch {
                 subScenario: `config with --isolatedModules and --declaration/${input.subScenario}`,
                 configFile: () => changeCompilerOptions(input, { isolatedModules: true, declaration: true })
             });
+
+            verifyEmitAndErrorUpdatesWorker({
+                ...input,
+                subScenario: `config with --assumeChangesOnlyAffectDirectDependencies/${input.subScenario}`,
+                configFile: () => changeCompilerOptions(input, { assumeChangesOnlyAffectDirectDependencies: true })
+            });
+
+            verifyEmitAndErrorUpdatesWorker({
+                ...input,
+                subScenario: `config with --assumeChangesOnlyAffectDirectDependencies and --declaration/${input.subScenario}`,
+                configFile: () => changeCompilerOptions(input, { assumeChangesOnlyAffectDirectDependencies: true, declaration: true })
+            });
         }
 
         describe("deep import changes", () => {

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

@@ -2673,6 +2673,7 @@ declare namespace ts {
         noUnusedLocals?: boolean;
         noUnusedParameters?: boolean;
         noImplicitUseStrict?: boolean;
+        assumeChangesOnlyAffectDirectDependencies?: boolean;
         noLib?: boolean;
         noResolve?: boolean;
         out?: string;
@@ -4779,6 +4780,7 @@ declare namespace ts {
         force?: boolean;
         verbose?: boolean;
         incremental?: boolean;
+        assumeChangesOnlyAffectDirectDependencies?: boolean;
         traceResolution?: boolean;
         [option: string]: CompilerOptionsValue | undefined;
     }

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

@@ -2673,6 +2673,7 @@ declare namespace ts {
         noUnusedLocals?: boolean;
         noUnusedParameters?: boolean;
         noImplicitUseStrict?: boolean;
+        assumeChangesOnlyAffectDirectDependencies?: boolean;
         noLib?: boolean;
         noResolve?: boolean;
         out?: string;
@@ -4779,6 +4780,7 @@ declare namespace ts {
         force?: boolean;
         verbose?: boolean;
         incremental?: boolean;
+        assumeChangesOnlyAffectDirectDependencies?: boolean;
         traceResolution?: boolean;
         [option: string]: CompilerOptionsValue | undefined;
     }

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

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

tests/baselines/reference/tscWatch/emitAndErrorUpdates/config-with---assumeChangesOnlyAffectDirectDependencies-and---declaration/deep-import-changes/updates-errors-when-deep-import-file-changes.js

@@ -0,0 +1,203 @@
+/a/lib/tsc.js --w
+//// [/user/username/projects/myproject/a.ts]
+import {B} from './b';
+declare var console: any;
+let b = new B();
+console.log(b.c.d);
+
+//// [/user/username/projects/myproject/b.ts]
+import {C} from './c';
+export class B
+{
+    c = new C();
+}
+
+//// [/user/username/projects/myproject/c.ts]
+export class C
+{
+    d = 1;
+}
+
+//// [/user/username/projects/myproject/tsconfig.json]
+{"compilerOptions":{"assumeChangesOnlyAffectDirectDependencies":true,"declaration":true}}
+
+//// [/a/lib/lib.d.ts]
+/// <reference no-default-lib="true"/>
+interface Boolean {}
+interface Function {}
+interface CallableFunction {}
+interface NewableFunction {}
+interface IArguments {}
+interface Number { toExponential: any; }
+interface Object {}
+interface RegExp {}
+interface String { charAt: any; }
+interface Array<T> { length: number; [n: number]: T; }
+
+//// [/user/username/projects/myproject/c.js]
+"use strict";
+exports.__esModule = true;
+var C = /** @class */ (function () {
+    function C() {
+        this.d = 1;
+    }
+    return C;
+}());
+exports.C = C;
+
+
+//// [/user/username/projects/myproject/c.d.ts]
+export declare class C {
+    d: number;
+}
+
+
+//// [/user/username/projects/myproject/b.js]
+"use strict";
+exports.__esModule = true;
+var c_1 = require("./c");
+var B = /** @class */ (function () {
+    function B() {
+        this.c = new c_1.C();
+    }
+    return B;
+}());
+exports.B = B;
+
+
+//// [/user/username/projects/myproject/b.d.ts]
+import { C } from './c';
+export declare class B {
+    c: C;
+}
+
+
+//// [/user/username/projects/myproject/a.js]
+"use strict";
+exports.__esModule = true;
+var b_1 = require("./b");
+var b = new b_1.B();
+console.log(b.c.d);
+
+
+//// [/user/username/projects/myproject/a.d.ts]
+export {};
+
+
+
+Output::
+>> Screen clear
+12:00:25 AM - Starting compilation in watch mode...
+
+
+
+12:00:38 AM - Found 0 errors. Watching for file changes.
+
+
+Program root files: ["/user/username/projects/myproject/a.ts","/user/username/projects/myproject/b.ts","/user/username/projects/myproject/c.ts"]
+Program options: {"assumeChangesOnlyAffectDirectDependencies":true,"declaration":true,"watch":true,"configFilePath":"/user/username/projects/myproject/tsconfig.json"}
+Program files::
+/a/lib/lib.d.ts
+/user/username/projects/myproject/c.ts
+/user/username/projects/myproject/b.ts
+/user/username/projects/myproject/a.ts
+
+Semantic diagnostics in builder refreshed for::
+/a/lib/lib.d.ts
+/user/username/projects/myproject/c.ts
+/user/username/projects/myproject/b.ts
+/user/username/projects/myproject/a.ts
+
+WatchedFiles::
+/user/username/projects/myproject/tsconfig.json:
+  {"pollingInterval":250}
+/user/username/projects/myproject/a.ts:
+  {"pollingInterval":250}
+/user/username/projects/myproject/b.ts:
+  {"pollingInterval":250}
+/user/username/projects/myproject/c.ts:
+  {"pollingInterval":250}
+/a/lib/lib.d.ts:
+  {"pollingInterval":250}
+
+FsWatches::
+
+FsWatchesRecursive::
+/user/username/projects/myproject/node_modules/@types:
+  {"fallbackPollingInterval":500,"fallbackOptions":{"watchFile":"PriorityPollingInterval"}}
+/user/username/projects/myproject:
+  {"fallbackPollingInterval":500,"fallbackOptions":{"watchFile":"PriorityPollingInterval"}}
+
+exitCode:: ExitStatus.undefined
+
+Change:: Rename property d to d2 of class C
+
+//// [/user/username/projects/myproject/c.ts]
+export class C
+{
+    d2 = 1;
+}
+
+//// [/user/username/projects/myproject/c.js]
+"use strict";
+exports.__esModule = true;
+var C = /** @class */ (function () {
+    function C() {
+        this.d2 = 1;
+    }
+    return C;
+}());
+exports.C = C;
+
+
+//// [/user/username/projects/myproject/c.d.ts]
+export declare class C {
+    d2: number;
+}
+
+
+//// [/user/username/projects/myproject/b.js] file written with same contents
+//// [/user/username/projects/myproject/b.d.ts] file written with same contents
+
+Output::
+>> Screen clear
+12:00:42 AM - File change detected. Starting incremental compilation...
+
+
+
+12:00:55 AM - Found 0 errors. Watching for file changes.
+
+
+Program root files: ["/user/username/projects/myproject/a.ts","/user/username/projects/myproject/b.ts","/user/username/projects/myproject/c.ts"]
+Program options: {"assumeChangesOnlyAffectDirectDependencies":true,"declaration":true,"watch":true,"configFilePath":"/user/username/projects/myproject/tsconfig.json"}
+Program files::
+/a/lib/lib.d.ts
+/user/username/projects/myproject/c.ts
+/user/username/projects/myproject/b.ts
+/user/username/projects/myproject/a.ts
+
+Semantic diagnostics in builder refreshed for::
+/user/username/projects/myproject/c.ts
+/user/username/projects/myproject/b.ts
+
+WatchedFiles::
+/user/username/projects/myproject/tsconfig.json:
+  {"pollingInterval":250}
+/user/username/projects/myproject/a.ts:
+  {"pollingInterval":250}
+/user/username/projects/myproject/b.ts:
+  {"pollingInterval":250}
+/user/username/projects/myproject/c.ts:
+  {"pollingInterval":250}
+/a/lib/lib.d.ts:
+  {"pollingInterval":250}
+
+FsWatches::
+
+FsWatchesRecursive::
+/user/username/projects/myproject/node_modules/@types:
+  {"fallbackPollingInterval":500,"fallbackOptions":{"watchFile":"PriorityPollingInterval"}}
+/user/username/projects/myproject:
+  {"fallbackPollingInterval":500,"fallbackOptions":{"watchFile":"PriorityPollingInterval"}}
+
+exitCode:: ExitStatus.undefined