Collect import helper needs during module info gathering (#21567) (#21586)

* Collect import helper needs during module info gathering

* Add tests for other forms that trigger import helpers

src/compiler/factory.ts

@@ -4293,7 +4293,7 @@ namespace ts {
         return emitNode && emitNode.externalHelpersModuleName;
     }
 
-    export function getOrCreateExternalHelpersModuleNameIfNeeded(node: SourceFile, compilerOptions: CompilerOptions, hasExportStarsToExportValues?: boolean) {
+    export function getOrCreateExternalHelpersModuleNameIfNeeded(node: SourceFile, compilerOptions: CompilerOptions, hasExportStarsToExportValues?: boolean, hasImportStarOrImportDefault?: boolean) {
         if (compilerOptions.importHelpers && isEffectiveExternalModule(node, compilerOptions)) {
             const externalHelpersModuleName = getExternalHelpersModuleName(node);
             if (externalHelpersModuleName) {
@@ -4301,7 +4301,7 @@ namespace ts {
             }
 
             const moduleKind = getEmitModuleKind(compilerOptions);
-            let create = hasExportStarsToExportValues
+            let create = (hasExportStarsToExportValues || (compilerOptions.esModuleInterop && hasImportStarOrImportDefault))
                 && moduleKind !== ModuleKind.System
                 && moduleKind !== ModuleKind.ES2015
                 && moduleKind !== ModuleKind.ESNext;

src/compiler/transformers/module/module.ts

@@ -690,36 +690,15 @@ namespace ts {
             return createCall(createPropertyAccess(promiseResolveCall, "then"), /*typeArguments*/ undefined, [func]);
         }
 
-        function getNamedImportCount(node: ImportDeclaration) {
-            if (!(node.importClause && node.importClause.namedBindings)) return 0;
-            const names = node.importClause.namedBindings;
-            if (!names) return 0;
-            if (!isNamedImports(names)) return 0;
-            return names.elements.length;
-        }
-
-        function containsDefaultReference(node: NamedImportBindings) {
-            if (!node) return false;
-            if (!isNamedImports(node)) return false;
-            return some(node.elements, isNamedDefaultReference);
-        }
-
-        function isNamedDefaultReference(e: ImportSpecifier) {
-            return e.propertyName && e.propertyName.escapedText === InternalSymbolName.Default;
-        }
-
         function getHelperExpressionForImport(node: ImportDeclaration, innerExpr: Expression) {
             if (!compilerOptions.esModuleInterop || getEmitFlags(node) & EmitFlags.NeverApplyImportHelper) {
                 return innerExpr;
             }
-            const nameCount = getNamedImportCount(node);
-            const hasDefault = nameCount > 0 ? containsDefaultReference(node.importClause.namedBindings) : undefined;
-
-            if (getNamespaceDeclarationNode(node) || (nameCount > 1 && hasDefault)) {
+            if (getImportNeedsImportStarHelper(node)) {
                 context.requestEmitHelper(importStarHelper);
                 return createCall(getHelperName("__importStar"), /*typeArguments*/ undefined, [innerExpr]);
             }
-            if (isDefaultImport(node) || (nameCount === 1 && hasDefault)) {
+            if (getImportNeedsImportDefaultHelper(node)) {
                 context.requestEmitHelper(importDefaultHelper);
                 return createCall(getHelperName("__importDefault"), /*typeArguments*/ undefined, [innerExpr]);
             }

src/compiler/transformers/utilities.ts

@@ -15,6 +15,32 @@ namespace ts {
         hasExportStarsToExportValues: boolean; // whether this module contains export*
     }
 
+    function getNamedImportCount(node: ImportDeclaration) {
+        if (!(node.importClause && node.importClause.namedBindings)) return 0;
+        const names = node.importClause.namedBindings;
+        if (!names) return 0;
+        if (!isNamedImports(names)) return 0;
+        return names.elements.length;
+    }
+
+    function containsDefaultReference(node: NamedImportBindings) {
+        if (!node) return false;
+        if (!isNamedImports(node)) return false;
+        return some(node.elements, isNamedDefaultReference);
+    }
+
+    function isNamedDefaultReference(e: ImportSpecifier) {
+        return e.propertyName && e.propertyName.escapedText === InternalSymbolName.Default;
+    }
+
+    export function getImportNeedsImportStarHelper(node: ImportDeclaration) {
+        return !!getNamespaceDeclarationNode(node) || (getNamedImportCount(node) > 1 && containsDefaultReference(node.importClause.namedBindings));
+    }
+
+    export function getImportNeedsImportDefaultHelper(node: ImportDeclaration) {
+        return isDefaultImport(node) || (getNamedImportCount(node) === 1 && containsDefaultReference(node.importClause.namedBindings));
+    }
+
     export function collectExternalModuleInfo(sourceFile: SourceFile, resolver: EmitResolver, compilerOptions: CompilerOptions): ExternalModuleInfo {
         const externalImports: (ImportDeclaration | ImportEqualsDeclaration | ExportDeclaration)[] = [];
         const exportSpecifiers = createMultiMap<ExportSpecifier>();
@@ -24,6 +50,7 @@ namespace ts {
         let hasExportDefault = false;
         let exportEquals: ExportAssignment = undefined;
         let hasExportStarsToExportValues = false;
+        let hasImportStarOrImportDefault = false;
 
         for (const node of sourceFile.statements) {
             switch (node.kind) {
@@ -33,6 +60,7 @@ namespace ts {
                     // import * as x from "mod"
                     // import { x, y } from "mod"
                     externalImports.push(<ImportDeclaration>node);
+                    hasImportStarOrImportDefault = getImportNeedsImportStarHelper(<ImportDeclaration>node) || getImportNeedsImportDefaultHelper(<ImportDeclaration>node);
                     break;
 
                 case SyntaxKind.ImportEqualsDeclaration:
@@ -135,7 +163,7 @@ namespace ts {
             }
         }
 
-        const externalHelpersModuleName = getOrCreateExternalHelpersModuleNameIfNeeded(sourceFile, compilerOptions, hasExportStarsToExportValues);
+        const externalHelpersModuleName = getOrCreateExternalHelpersModuleNameIfNeeded(sourceFile, compilerOptions, hasExportStarsToExportValues, hasImportStarOrImportDefault);
         const externalHelpersImportDeclaration = externalHelpersModuleName && createImportDeclaration(
             /*decorators*/ undefined,
             /*modifiers*/ undefined,

tests/baselines/reference/esModuleInteropTslibHelpers.js

@@ -0,0 +1,64 @@
+//// [tests/cases/compiler/esModuleInteropTslibHelpers.ts] ////
+
+//// [refs.d.ts]
+declare module "path";
+//// [file.ts]
+import path from "path";
+path.resolve("", "../");
+export class Foo { }
+//// [file2.ts]
+import * as path from "path";
+path.resolve("", "../");
+export class Foo2 { }
+//// [file3.ts]
+import {default as resolve} from "path";
+resolve("", "../");
+export class Foo3 { }
+//// [file4.ts]
+import {Bar, default as resolve} from "path";
+resolve("", "../");
+export { Bar }
+
+//// [file.js]
+"use strict";
+exports.__esModule = true;
+var tslib_1 = require("tslib");
+var path_1 = tslib_1.__importDefault(require("path"));
+path_1["default"].resolve("", "../");
+var Foo = /** @class */ (function () {
+    function Foo() {
+    }
+    return Foo;
+}());
+exports.Foo = Foo;
+//// [file2.js]
+"use strict";
+exports.__esModule = true;
+var tslib_1 = require("tslib");
+var path = tslib_1.__importStar(require("path"));
+path.resolve("", "../");
+var Foo2 = /** @class */ (function () {
+    function Foo2() {
+    }
+    return Foo2;
+}());
+exports.Foo2 = Foo2;
+//// [file3.js]
+"use strict";
+exports.__esModule = true;
+var tslib_1 = require("tslib");
+var path_1 = tslib_1.__importDefault(require("path"));
+path_1["default"]("", "../");
+var Foo3 = /** @class */ (function () {
+    function Foo3() {
+    }
+    return Foo3;
+}());
+exports.Foo3 = Foo3;
+//// [file4.js]
+"use strict";
+exports.__esModule = true;
+var tslib_1 = require("tslib");
+var path_1 = tslib_1.__importStar(require("path"));
+exports.Bar = path_1.Bar;
+path_1["default"]("", "../");

tests/baselines/reference/esModuleInteropTslibHelpers.symbols

@@ -0,0 +1,45 @@
+=== tests/cases/compiler/refs.d.ts ===
+declare module "path";
+No type information for this code.=== tests/cases/compiler/file.ts ===
+import path from "path";
+>path : Symbol(path, Decl(file.ts, 0, 6))
+
+path.resolve("", "../");
+>path : Symbol(path, Decl(file.ts, 0, 6))
+
+export class Foo { }
+>Foo : Symbol(Foo, Decl(file.ts, 1, 24))
+
+=== tests/cases/compiler/file2.ts ===
+import * as path from "path";
+>path : Symbol(path, Decl(file2.ts, 0, 6))
+
+path.resolve("", "../");
+>path : Symbol(path, Decl(file2.ts, 0, 6))
+
+export class Foo2 { }
+>Foo2 : Symbol(Foo2, Decl(file2.ts, 1, 24))
+
+=== tests/cases/compiler/file3.ts ===
+import {default as resolve} from "path";
+>default : Symbol(resolve, Decl(file3.ts, 0, 8))
+>resolve : Symbol(resolve, Decl(file3.ts, 0, 8))
+
+resolve("", "../");
+>resolve : Symbol(resolve, Decl(file3.ts, 0, 8))
+
+export class Foo3 { }
+>Foo3 : Symbol(Foo3, Decl(file3.ts, 1, 19))
+
+=== tests/cases/compiler/file4.ts ===
+import {Bar, default as resolve} from "path";
+>Bar : Symbol(Bar, Decl(file4.ts, 0, 8))
+>default : Symbol(resolve, Decl(file4.ts, 0, 12))
+>resolve : Symbol(resolve, Decl(file4.ts, 0, 12))
+
+resolve("", "../");
+>resolve : Symbol(resolve, Decl(file4.ts, 0, 12))
+
+export { Bar }
+>Bar : Symbol(Bar, Decl(file4.ts, 2, 8))
+

tests/baselines/reference/esModuleInteropTslibHelpers.types

@@ -0,0 +1,61 @@
+=== tests/cases/compiler/refs.d.ts ===
+declare module "path";
+No type information for this code.=== tests/cases/compiler/file.ts ===
+import path from "path";
+>path : any
+
+path.resolve("", "../");
+>path.resolve("", "../") : any
+>path.resolve : any
+>path : any
+>resolve : any
+>"" : ""
+>"../" : "../"
+
+export class Foo { }
+>Foo : Foo
+
+=== tests/cases/compiler/file2.ts ===
+import * as path from "path";
+>path : any
+
+path.resolve("", "../");
+>path.resolve("", "../") : any
+>path.resolve : any
+>path : any
+>resolve : any
+>"" : ""
+>"../" : "../"
+
+export class Foo2 { }
+>Foo2 : Foo2
+
+=== tests/cases/compiler/file3.ts ===
+import {default as resolve} from "path";
+>default : any
+>resolve : any
+
+resolve("", "../");
+>resolve("", "../") : any
+>resolve : any
+>"" : ""
+>"../" : "../"
+
+export class Foo3 { }
+>Foo3 : Foo3
+
+=== tests/cases/compiler/file4.ts ===
+import {Bar, default as resolve} from "path";
+>Bar : any
+>default : any
+>resolve : any
+
+resolve("", "../");
+>resolve("", "../") : any
+>resolve : any
+>"" : ""
+>"../" : "../"
+
+export { Bar }
+>Bar : any
+

tests/cases/compiler/esModuleInteropTslibHelpers.ts

@@ -0,0 +1,21 @@
+// @esModuleInterop: true
+// @importHelpers: true
+// @noEmitHelpers: true
+// @filename: refs.d.ts
+declare module "path";
+// @filename: file.ts
+import path from "path";
+path.resolve("", "../");
+export class Foo { }
+// @filename: file2.ts
+import * as path from "path";
+path.resolve("", "../");
+export class Foo2 { }
+// @filename: file3.ts
+import {default as resolve} from "path";
+resolve("", "../");
+export class Foo3 { }
+// @filename: file4.ts
+import {Bar, default as resolve} from "path";
+resolve("", "../");
+export { Bar }