Import assertion

src/compiler/checker.ts

@@ -39000,11 +39000,11 @@ namespace ts {
         function checkAssertClause(declaration: ImportDeclaration | ExportDeclaration) {
             if (declaration.assertClause) {
                 if (moduleKind !== ModuleKind.ESNext) {
-                    error(declaration.assertClause, Diagnostics.Import_assertions_are_only_supported_when_the_module_option_is_set_to_esnext);
+                    return grammarErrorOnNode(declaration.assertClause, Diagnostics.Import_assertions_are_only_supported_when_the_module_option_is_set_to_esnext);
                 }
 
                 if (isImportDeclaration(declaration) ? declaration.importClause?.isTypeOnly : declaration.isTypeOnly) {
-                    error(declaration.assertClause, Diagnostics.Import_assertions_cannot_be_used_with_type_only_imports_or_exports);
+                    return grammarErrorOnNode(declaration.assertClause, Diagnostics.Import_assertions_cannot_be_used_with_type_only_imports_or_exports);
                 }
             }
         }
@@ -43162,7 +43162,16 @@ namespace ts {
             return false;
         }
 
-        function checkGrammarImportCallArguments(node: ImportCall, nodeArguments: NodeArray<Expression>): boolean {
+        function checkGrammarImportCallExpression(node: ImportCall): boolean {
+            if (moduleKind === ModuleKind.ES2015) {
+                return grammarErrorOnNode(node, Diagnostics.Dynamic_imports_are_only_supported_when_the_module_flag_is_set_to_es2020_esnext_commonjs_amd_system_or_umd);
+            }
+
+            if (node.typeArguments) {
+                return grammarErrorOnNode(node, Diagnostics.Dynamic_import_cannot_have_type_arguments);
+            }
+
+            const nodeArguments = node.arguments;
             if (moduleKind !== ModuleKind.ESNext) {
                 // We are allowed trailing comma after proposal-import-assertions.
                 checkGrammarForDisallowedTrailingComma(nodeArguments);
@@ -43172,28 +43181,15 @@ namespace ts {
                     return grammarErrorOnNode(assertionArgument, Diagnostics.Dynamic_import_only_supports_a_second_argument_when_the_module_option_is_set_to_esnext);
                 }
             }
-            if (nodeArguments.length !== 1) {
-                return grammarErrorOnNode(node, Diagnostics.Dynamic_import_must_only_have_a_specifier_and_an_optional_assertion_as_arguments);
-            }
-            return false;
-        }
-
-        function checkGrammarImportCallExpression(node: ImportCall): boolean {
-            if (moduleKind === ModuleKind.ES2015) {
-                return grammarErrorOnNode(node, Diagnostics.Dynamic_imports_are_only_supported_when_the_module_flag_is_set_to_es2020_esnext_commonjs_amd_system_or_umd);
-            }
 
-            if (node.typeArguments) {
-                return grammarErrorOnNode(node, Diagnostics.Dynamic_import_cannot_have_type_arguments);
+            if (nodeArguments.length  === 0 || nodeArguments.length > 2) {
+                return grammarErrorOnNode(node, Diagnostics.Dynamic_import_must_only_have_a_specifier_and_an_optional_assertion_as_arguments);
             }
 
-            const nodeArguments = node.arguments;
-            if (checkGrammarImportCallArguments(node, nodeArguments)) {
-                return true;
-            }
             // see: parseArgumentOrArrayLiteralElement...we use this function which parse arguments of callExpression to parse specifier for dynamic import.
             // parseArgumentOrArrayLiteralElement allows spread element to be in an argument list which is not allowed as specifier in dynamic import.
-            if (nodeArguments.length && isSpreadElement(nodeArguments[0])) {
+            const spreadElement = forEach(nodeArguments, isSpreadElement);
+            if (spreadElement) {
                 return grammarErrorOnNode(nodeArguments[0], Diagnostics.Specifier_of_dynamic_import_cannot_be_spread_element);
             }
             return false;

src/compiler/diagnosticMessages.json

@@ -1372,9 +1372,25 @@
         "category": "Error",
         "code": 1443
     },
+    "'{0}' is a type and must be imported using a type-only import when 'preserveValueImports' and 'isolatedModules' are both enabled.": {
+        "category": "Error",
+        "code": 1444
+    },
+    "'{0}' resolves to a type-only declaration and must be imported using a type-only import when 'preserveValueImports' and 'isolatedModules' are both enabled.": {
+        "category": "Error",
+        "code": 1446
+    },
+    "'{0}' resolves to a type-only declaration and must be re-exported using a type-only re-export when 'isolatedModules' is enabled.": {
+        "category": "Error",
+        "code": 1448
+    },
+    "Preserve unused imported values in the JavaScript output that would otherwise be removed.": {
+        "category": "Message",
+        "code": 1449
+    },
     "Dynamic import must only have a specifier and an optional assertion as arguments": {
         "category": "Message",
-        "code": 1444
+        "code": 1450
     },
 
     "The types of '{0}' are incompatible between these types.": {

src/compiler/emitter.ts

@@ -3327,8 +3327,7 @@ namespace ts {
             }
             emitExpression(node.moduleSpecifier);
             if (node.assertClause) {
-                writeSpace();
-                emit(node.assertClause);
+                emitWithLeadingSpace(node.assertClause);
             }
             writeTrailingSemicolon();
         }
@@ -3399,8 +3398,7 @@ namespace ts {
                 emitExpression(node.moduleSpecifier);
             }
             if (node.assertClause) {
-                writeSpace();
-                emit(node.assertClause);
+                emitWithLeadingSpace(node.assertClause);
             }
             writeTrailingSemicolon();
         }

src/compiler/types.ts

@@ -7341,8 +7341,8 @@ namespace ts {
         updateNamespaceExportDeclaration(node: NamespaceExportDeclaration, name: Identifier): NamespaceExportDeclaration;
         createImportEqualsDeclaration(decorators: readonly Decorator[] | undefined, modifiers: readonly Modifier[] | undefined, isTypeOnly: boolean, name: string | Identifier, moduleReference: ModuleReference): ImportEqualsDeclaration;
         updateImportEqualsDeclaration(node: ImportEqualsDeclaration, decorators: readonly Decorator[] | undefined, modifiers: readonly Modifier[] | undefined, isTypeOnly: boolean, name: Identifier, moduleReference: ModuleReference): ImportEqualsDeclaration;
-        createImportDeclaration(decorators: readonly Decorator[] | undefined, modifiers: readonly Modifier[] | undefined, importClause: ImportClause | undefined, moduleSpecifier: Expression, assertClause: AssertClause | undefined): ImportDeclaration;
-        updateImportDeclaration(node: ImportDeclaration, decorators: readonly Decorator[] | undefined, modifiers: readonly Modifier[] | undefined, importClause: ImportClause | undefined, moduleSpecifier: Expression, assertClause: AssertClause | undefined): ImportDeclaration;
+        createImportDeclaration(decorators: readonly Decorator[] | undefined, modifiers: readonly Modifier[] | undefined, importClause: ImportClause | undefined, moduleSpecifier: Expression, assertClause?: AssertClause): ImportDeclaration;
+        updateImportDeclaration(node: ImportDeclaration, decorators: readonly Decorator[] | undefined, modifiers: readonly Modifier[] | undefined, importClause: ImportClause | undefined, moduleSpecifier: Expression, assertClause?: AssertClause): ImportDeclaration;
         createImportClause(isTypeOnly: boolean, name: Identifier | undefined, namedBindings: NamedImportBindings | undefined): ImportClause;
         updateImportClause(node: ImportClause, isTypeOnly: boolean, name: Identifier | undefined, namedBindings: NamedImportBindings | undefined): ImportClause;
         createAssertClause(elements: NodeArray<AssertEntry>, multiLine?: boolean): AssertClause;
@@ -7360,7 +7360,7 @@ namespace ts {
         createExportAssignment(decorators: readonly Decorator[] | undefined, modifiers: readonly Modifier[] | undefined, isExportEquals: boolean | undefined, expression: Expression): ExportAssignment;
         updateExportAssignment(node: ExportAssignment, decorators: readonly Decorator[] | undefined, modifiers: readonly Modifier[] | undefined, expression: Expression): ExportAssignment;
         createExportDeclaration(decorators: readonly Decorator[] | undefined, modifiers: readonly Modifier[] | undefined, isTypeOnly: boolean, exportClause: NamedExportBindings | undefined, moduleSpecifier?: Expression, assertClause?: AssertClause): ExportDeclaration;
-        updateExportDeclaration(node: ExportDeclaration, decorators: readonly Decorator[] | undefined, modifiers: readonly Modifier[] | undefined, isTypeOnly: boolean, exportClause: NamedExportBindings | undefined, moduleSpecifier: Expression | undefined, assertClause: AssertClause | undefined): ExportDeclaration;
+        updateExportDeclaration(node: ExportDeclaration, decorators: readonly Decorator[] | undefined, modifiers: readonly Modifier[] | undefined, isTypeOnly: boolean, exportClause: NamedExportBindings | undefined, moduleSpecifier: Expression | undefined, assertClause?: AssertClause): ExportDeclaration;
         createNamedExports(elements: readonly ExportSpecifier[]): NamedExports;
         updateNamedExports(node: NamedExports, elements: readonly ExportSpecifier[]): NamedExports;
         createExportSpecifier(propertyName: string | Identifier | undefined, name: string | Identifier): ExportSpecifier;

src/compiler/utilitiesPublic.ts

@@ -1378,7 +1378,6 @@ namespace ts {
     /* @internal */
     export function isAssignmentPattern(node: Node): node is AssignmentPattern {
         const kind = node.kind;
-
         return kind === SyntaxKind.ArrayLiteralExpression
             || kind === SyntaxKind.ObjectLiteralExpression;
     }

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

@@ -4368,7 +4368,7 @@ declare namespace ts {
     function isTemplateLiteralToken(node: Node): node is TemplateLiteralToken;
     function isTemplateMiddleOrTemplateTail(node: Node): node is TemplateMiddle | TemplateTail;
     function isImportOrExportSpecifier(node: Node): node is ImportSpecifier | ExportSpecifier;
-    function isTypeOnlyImportOrExportDeclaration(node: Node): node is TypeOnlyCompatibleAliasDeclaration;
+    function isTypeOnlyImportOrExportDeclaration(node: Node): node is TypeOnlyAliasDeclaration;
     function isAssertionKey(node: Node): node is AssertionKey;
     function isStringTextContainingNode(node: Node): node is StringLiteral | TemplateLiteralToken;
     function isModifier(node: Node): node is Modifier;

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

@@ -4368,7 +4368,7 @@ declare namespace ts {
     function isTemplateLiteralToken(node: Node): node is TemplateLiteralToken;
     function isTemplateMiddleOrTemplateTail(node: Node): node is TemplateMiddle | TemplateTail;
     function isImportOrExportSpecifier(node: Node): node is ImportSpecifier | ExportSpecifier;
-    function isTypeOnlyImportOrExportDeclaration(node: Node): node is TypeOnlyCompatibleAliasDeclaration;
+    function isTypeOnlyImportOrExportDeclaration(node: Node): node is TypeOnlyAliasDeclaration;
     function isAssertionKey(node: Node): node is AssertionKey;
     function isStringTextContainingNode(node: Node): node is StringLiteral | TemplateLiteralToken;
     function isModifier(node: Node): node is Modifier;

tests/baselines/reference/importAssertion1(module=commonjs).errors.txt

@@ -8,7 +8,7 @@ tests/cases/conformance/importAssertion/3.ts(3,25): error TS1324: Dynamic import
 tests/cases/conformance/importAssertion/3.ts(4,25): error TS1324: Dynamic import only supports a second argument when the '--module' option is set to 'esnext'.
 tests/cases/conformance/importAssertion/3.ts(5,26): error TS1324: Dynamic import only supports a second argument when the '--module' option is set to 'esnext'.
 tests/cases/conformance/importAssertion/3.ts(7,25): error TS1324: Dynamic import only supports a second argument when the '--module' option is set to 'esnext'.
-tests/cases/conformance/importAssertion/3.ts(8,11): message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
+tests/cases/conformance/importAssertion/3.ts(8,11): message TS1450: Dynamic import must only have a specifier and an optional assertion as arguments
 tests/cases/conformance/importAssertion/3.ts(9,25): error TS1324: Dynamic import only supports a second argument when the '--module' option is set to 'esnext'.
 tests/cases/conformance/importAssertion/3.ts(10,25): error TS1324: Dynamic import only supports a second argument when the '--module' option is set to 'esnext'.
 tests/cases/conformance/importAssertion/3.ts(10,52): error TS1009: Trailing comma not allowed.
@@ -65,7 +65,7 @@ tests/cases/conformance/importAssertion/3.ts(10,52): error TS1009: Trailing comm
 !!! error TS1324: Dynamic import only supports a second argument when the '--module' option is set to 'esnext'.
     const f = import()
               ~~~~~~~~
-!!! message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
+!!! message TS1450: Dynamic import must only have a specifier and an optional assertion as arguments
     const g = import('./0', {}, {})
                             ~~
 !!! error TS1324: Dynamic import only supports a second argument when the '--module' option is set to 'esnext'.

tests/baselines/reference/importAssertion1(module=esnext).errors.txt

@@ -1,11 +1,5 @@
-tests/cases/conformance/importAssertion/3.ts(2,11): message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
-tests/cases/conformance/importAssertion/3.ts(3,11): message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
-tests/cases/conformance/importAssertion/3.ts(4,11): message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
-tests/cases/conformance/importAssertion/3.ts(5,12): message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
-tests/cases/conformance/importAssertion/3.ts(7,11): message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
-tests/cases/conformance/importAssertion/3.ts(8,11): message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
-tests/cases/conformance/importAssertion/3.ts(9,11): message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
-tests/cases/conformance/importAssertion/3.ts(10,11): message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
+tests/cases/conformance/importAssertion/3.ts(8,11): message TS1450: Dynamic import must only have a specifier and an optional assertion as arguments
+tests/cases/conformance/importAssertion/3.ts(9,11): message TS1450: Dynamic import must only have a specifier and an optional assertion as arguments
 
 
 ==== tests/cases/conformance/importAssertion/0.ts (0 errors) ====
@@ -29,32 +23,20 @@ tests/cases/conformance/importAssertion/3.ts(10,11): message TS1444: Dynamic imp
     c;
     d;
 
-==== tests/cases/conformance/importAssertion/3.ts (8 errors) ====
+==== tests/cases/conformance/importAssertion/3.ts (2 errors) ====
     const a = import('./0')
     const b = import('./0', { assert: { type: "json" } })
-              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
     const c = import('./0', { assert: { type: "json", ttype: "typo" } })
-              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
     const d = import('./0', { assert: {} })
-              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
     const dd = import('./0', {})
-               ~~~~~~~~~~~~~~~~~
-!!! message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
     declare function foo(): any;
     const e = import('./0', foo())
-              ~~~~~~~~~~~~~~~~~~~~
-!!! message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
     const f = import()
               ~~~~~~~~
-!!! message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
+!!! message TS1450: Dynamic import must only have a specifier and an optional assertion as arguments
     const g = import('./0', {}, {})
               ~~~~~~~~~~~~~~~~~~~~~
-!!! message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
+!!! message TS1450: Dynamic import must only have a specifier and an optional assertion as arguments
     const h = import('./0', { assert: { type: "json" }},)
-              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! message TS1444: Dynamic import must only have a specifier and an optional assertion as arguments
 
 

tests/baselines/reference/importAssertion3(module=es2015).errors.txt

@@ -1,38 +1,26 @@
 tests/cases/conformance/importAssertion/1.ts(1,27): error TS2820: Import assertions are only supported when the '--module' option is set to 'esnext'.
-tests/cases/conformance/importAssertion/1.ts(1,27): error TS2821: Import assertions cannot be used with type-only imports or exports.
 tests/cases/conformance/importAssertion/1.ts(2,30): error TS2820: Import assertions are only supported when the '--module' option is set to 'esnext'.
-tests/cases/conformance/importAssertion/1.ts(2,30): error TS2821: Import assertions cannot be used with type-only imports or exports.
 tests/cases/conformance/importAssertion/2.ts(1,31): error TS2820: Import assertions are only supported when the '--module' option is set to 'esnext'.
-tests/cases/conformance/importAssertion/2.ts(1,31): error TS2821: Import assertions cannot be used with type-only imports or exports.
 tests/cases/conformance/importAssertion/2.ts(2,33): error TS2820: Import assertions are only supported when the '--module' option is set to 'esnext'.
-tests/cases/conformance/importAssertion/2.ts(2,33): error TS2821: Import assertions cannot be used with type-only imports or exports.
 
 
 ==== tests/cases/conformance/importAssertion/0.ts (0 errors) ====
     export interface I { }
 
-==== tests/cases/conformance/importAssertion/1.ts (4 errors) ====
+==== tests/cases/conformance/importAssertion/1.ts (2 errors) ====
     export type {} from './0' assert { type: "json" }
                               ~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2820: Import assertions are only supported when the '--module' option is set to 'esnext'.
-                              ~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2821: Import assertions cannot be used with type-only imports or exports.
     export type { I } from './0' assert { type: "json" }
                                  ~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2820: Import assertions are only supported when the '--module' option is set to 'esnext'.
-                                 ~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2821: Import assertions cannot be used with type-only imports or exports.
 
-==== tests/cases/conformance/importAssertion/2.ts (4 errors) ====
+==== tests/cases/conformance/importAssertion/2.ts (2 errors) ====
     import type { I } from './0'  assert { type: "json" }
                                   ~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2820: Import assertions are only supported when the '--module' option is set to 'esnext'.
-                                  ~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2821: Import assertions cannot be used with type-only imports or exports.
     import type * as foo from './0' assert { type: "json" }
                                     ~~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2820: Import assertions are only supported when the '--module' option is set to 'esnext'.
-                                    ~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2821: Import assertions cannot be used with type-only imports or exports.