Add a new compiler option moduleSuffixes to expand the node module resolver's search algorithm (#48189)

* Add moduleSuffixes compiler option and related tests. Update baselines for compiler options tests.

* Add a flag to the command-line parser which allows "list" params to preserve "falsy" values such as empty strings. Falsy values are normally stripped out.

* Add tests. Rework resolver logic to only run module-suffix code when needed.

* PR feedback

* Add test

* Remove unnecessary conditional.

tests/cases/compiler/moduleResolutionWithSuffixes_empty.ts

@@ -0,0 +1,14 @@
+// moduleSuffixes is empty. Normal module resolution should occur.
+
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": []
+	}
+}
+// @filename: /index.ts
+import { base } from "./foo";
+// @filename: /foo.ts
+export function base() {}

tests/cases/compiler/moduleResolutionWithSuffixes_notSpecified.ts

@@ -0,0 +1,12 @@
+// moduleSuffixes is not specified. Normal module resolution should occur.
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"moduleResolution": "node",
+		"traceResolution": true,
+	}
+}
+// @filename: /index.ts
+import { base } from "./foo";
+// @filename: /foo.ts
+export function base() {}

tests/cases/compiler/moduleResolutionWithSuffixes_one.ts

@@ -0,0 +1,17 @@
+// moduleSuffixes has one entry and there's a matching file.
+
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": [".ios"]
+	}
+}
+
+// @filename: /index.ts
+import { ios } from "./foo";
+// @filename: /foo.ios.ts
+export function ios() {}
+// @filename: /foo.ts
+export function base() {}

tests/cases/compiler/moduleResolutionWithSuffixes_oneBlank.ts

@@ -0,0 +1,15 @@
+// moduleSuffixes has one blank entry. Normal module resolution should occur.
+
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": [""]
+	}
+}
+
+// @filename: /index.ts
+import { base } from "./foo";
+// @filename: /foo.ts
+export function base() {}

tests/cases/compiler/moduleResolutionWithSuffixes_oneNotFound.ts

@@ -0,0 +1,15 @@
+// moduleSuffixes has one entry but there isn't a matching file. Module resolution should fail.
+
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": [".ios"]
+	}
+}
+
+// @filename: /index.ts
+import { ios } from "./foo";
+// @filename: /foo.ts
+export function base() {}

tests/cases/compiler/moduleResolutionWithSuffixes_one_dirModuleWithIndex.ts

@@ -0,0 +1,17 @@
+// moduleSuffixes has one entry and there's a matching dir with an index file.
+
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": [".ios"]
+	}
+}
+
+// @filename: /index.ts
+import { ios } from "./foo";
+// @filename: /foo/index.ios.ts
+export function ios() {}
+// @filename: /foo/index.ts
+export function base() {}

tests/cases/compiler/moduleResolutionWithSuffixes_one_externalModule.ts

@@ -0,0 +1,31 @@
+// moduleSuffixes has one entry and there's a matching package.
+// @fullEmitPaths: true
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"allowJs": true,
+		"checkJs": false,
+		"outDir": "bin",
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": [".ios"]
+	}
+}
+
+// @filename: /node_modules/some-library/index.ios.js
+"use strict";
+exports.__esModule = true;
+function ios() {}
+exports.ios = ios;
+// @filename: /node_modules/some-library/index.ios.d.ts
+export declare function ios(): void;
+// @filename: /node_modules/some-library/index.js
+"use strict";
+exports.__esModule = true;
+function base() {}
+exports.base = base;
+// @filename: /node_modules/some-library/index.d.ts
+export declare function base(): void;
+
+// @filename: /index.ts
+import { ios } from "some-library";

tests/cases/compiler/moduleResolutionWithSuffixes_one_externalModulePath.ts

@@ -0,0 +1,31 @@
+// moduleSuffixes has one entry and there's a matching package with a specific path.
+// @fullEmitPaths: true
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"allowJs": true,
+		"checkJs": false,
+		"outDir": "bin",
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": [".ios"]
+	}
+}
+
+// @filename: /node_modules/some-library/foo.ios.js
+"use strict";
+exports.__esModule = true;
+function iosfoo() {}
+exports.iosfoo = iosfoo;
+// @filename: /node_modules/some-library/foo.ios.d.ts
+export declare function iosfoo(): void;
+// @filename: /node_modules/some-library/foo.js
+"use strict";
+exports.__esModule = true;
+function basefoo() {}
+exports.basefoo = basefoo;
+// @filename: /node_modules/some-library/foo.d.ts
+export declare function basefoo(): void;
+
+// @filename: /index.ts
+import { iosfoo } from "some-library/foo";

tests/cases/compiler/moduleResolutionWithSuffixes_one_externalModule_withPaths.ts

@@ -0,0 +1,38 @@
+// moduleSuffixes has one entry and there's a matching package. use the 'paths' option to map the package.
+// @fullEmitPaths: true
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"allowJs": true,
+		"checkJs": false,
+		"outDir": "bin",
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": [".ios"],
+		"baseUrl": "/",
+		"paths": {
+			"some-library": ["node_modules/some-library/lib"],
+			"some-library/*": ["node_modules/some-library/lib/*"]
+		}
+	}
+}
+
+// @filename: /node_modules/some-library/lib/index.ios.js
+"use strict";
+exports.__esModule = true;
+function ios() {}
+exports.ios = ios;
+// @filename: /node_modules/some-library/lib/index.ios.d.ts
+export declare function ios(): void;
+// @filename: /node_modules/some-library/lib/index.js
+"use strict";
+exports.__esModule = true;
+function base() {}
+exports.base = base;
+// @filename: /node_modules/some-library/lib/index.d.ts
+export declare function base(): void;
+
+// @filename: /test.ts
+import { ios } from "some-library";
+import { ios as ios2 } from "some-library/index";
+import { ios as ios3 } from "some-library/index.js";

tests/cases/compiler/moduleResolutionWithSuffixes_one_externalTSModule.ts

@@ -0,0 +1,18 @@
+// moduleSuffixes has one entry and there's a matching package with TS files.
+// @fullEmitPaths: true
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"outDir": "bin",
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": [".ios"]
+	}
+}
+
+// @filename: /node_modules/some-library/index.ios.ts
+export function ios() {}
+// @filename: /node_modules/some-library/index.ts
+export function base() {}
+// @filename: /test.ts
+import { ios } from "some-library";

tests/cases/compiler/moduleResolutionWithSuffixes_one_jsModule.ts

@@ -0,0 +1,26 @@
+// moduleSuffixes has one entry and there's a matching file. module name explicitly includes JS file extension.
+// @fullEmitPaths: true
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"allowJs": true,
+		"checkJs": false,
+		"outDir": "bin",
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": [".ios"]
+	}
+}
+
+// @filename: /index.ts
+import { ios } from "./foo.js";
+// @filename: /foo.ios.js
+"use strict";
+exports.__esModule = true;
+function ios() {}
+exports.ios = ios;
+// @filename: /foo.js
+"use strict";
+exports.__esModule = true;
+function base() {}
+exports.base = base;

tests/cases/compiler/moduleResolutionWithSuffixes_one_jsonModule.ts

@@ -0,0 +1,25 @@
+// moduleSuffixes has one entry and there's a matching file. module name explicitly includes JSON file extension.
+// @fullEmitPaths: true
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"esModuleInterop": true,
+		"resolveJsonModule": true,
+		"outDir": "bin",
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": [".ios"]
+	}
+}
+
+// @filename: /index.ts
+import foo from "./foo.json";
+console.log(foo.ios);
+// @filename: /foo.ios.json
+{
+	"ios": "platform ios"
+}
+// @filename: /foo.json
+{
+	"base": "platform base"
+}

tests/cases/compiler/moduleResolutionWithSuffixes_threeLastIsBlank1.ts

@@ -0,0 +1,19 @@
+// moduleSuffixes has three entries, and the last one is blank. Module resolution should match on the first suffix.
+
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": ["-ios", "__native", ""]
+	}
+}
+
+// @filename: /index.ts
+import { ios } from "./foo";
+// @filename: /foo-ios.ts
+export function ios() {}
+// @filename: /foo__native.ts
+export function native() {}
+// @filename: /foo.ts
+export function base() {}

tests/cases/compiler/moduleResolutionWithSuffixes_threeLastIsBlank2.ts

@@ -0,0 +1,17 @@
+// moduleSuffixes has three entries, and the last one is blank. Module resolution should match on the second suffix.
+
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": ["-ios", "__native", ""]
+	}
+}
+
+// @filename: /index.ts
+import { native } from "./foo";
+// @filename: /foo__native.ts
+export function native() {}
+// @filename: /foo.ts
+export function base() {}

tests/cases/compiler/moduleResolutionWithSuffixes_threeLastIsBlank3.ts

@@ -0,0 +1,15 @@
+// moduleSuffixes has three entries, and the last one is blank. Module resolution should match on the blank suffix.
+
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": ["-ios", "__native", ""]
+	}
+}
+
+// @filename: /index.ts
+import { base } from "./foo";
+// @filename: /foo.ts
+export function base() {}

tests/cases/compiler/moduleResolutionWithSuffixes_threeLastIsBlank4.ts

@@ -0,0 +1,13 @@
+// moduleSuffixes has three entries, and the last one is blank. Module resolution should fail.
+
+// @filename: /tsconfig.json
+{
+	"compilerOptions": {
+		"moduleResolution": "node",
+		"traceResolution": true,
+		"moduleSuffixes": ["-ios", "__native", ""]
+	}
+}
+
+// @filename: /index.ts
+import { base } from "./foo";