Add new option "noUncheckedSideEffectImports" (#58941)

src/compiler/checker.ts

@@ -720,6 +720,7 @@ import {
     isSetAccessorDeclaration,
     isShorthandAmbientModuleSymbol,
     isShorthandPropertyAssignment,
+    isSideEffectImport,
     isSingleOrDoubleQuote,
     isSourceFile,
     isSourceFileJS,
@@ -1505,6 +1506,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     var noImplicitThis = getStrictOptionValue(compilerOptions, "noImplicitThis");
     var useUnknownInCatchVariables = getStrictOptionValue(compilerOptions, "useUnknownInCatchVariables");
     var exactOptionalPropertyTypes = compilerOptions.exactOptionalPropertyTypes;
+    var noUncheckedSideEffectImports = !!compilerOptions.noUncheckedSideEffectImports;
 
     var checkBinaryExpression = createCheckBinaryExpression();
     var emitResolver = createResolver();
@@ -4660,7 +4662,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 // merged symbol is module declaration symbol combined with all augmentations
                 return getMergedSymbol(sourceFile.symbol);
             }
-            if (errorNode && moduleNotFoundError) {
+            if (errorNode && moduleNotFoundError && !isSideEffectImport(errorNode)) {
                 // report errors only if it was requested
                 error(errorNode, Diagnostics.File_0_is_not_a_module, sourceFile.fileName);
             }
@@ -4765,6 +4767,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     }
 
     function errorOnImplicitAnyModule(isError: boolean, errorNode: Node, sourceFile: SourceFile, mode: ResolutionMode, { packageId, resolvedFileName }: ResolvedModuleFull, moduleReference: string): void {
+        if (isSideEffectImport(errorNode)) {
+            return;
+        }
+
         let errorInfo: DiagnosticMessageChain | undefined;
         if (!isExternalModuleNameRelative(moduleReference) && packageId) {
             errorInfo = createModuleNotFoundChain(sourceFile, host, moduleReference, mode, packageId.name);
@@ -47246,6 +47252,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     }
                 }
             }
+            else if (noUncheckedSideEffectImports && !importClause) {
+                void resolveExternalModuleName(node, node.moduleSpecifier);
+            }
         }
         checkImportAttributes(node);
     }

src/compiler/commandLineParser.ts

@@ -1202,6 +1202,15 @@ const commandOptionsWithoutBuild: CommandLineOption[] = [
         category: Diagnostics.Modules,
         description: Diagnostics.Conditions_to_set_in_addition_to_the_resolver_specific_defaults_when_resolving_imports,
     },
+    {
+        name: "noUncheckedSideEffectImports",
+        type: "boolean",
+        affectsSemanticDiagnostics: true,
+        affectsBuildInfo: true,
+        category: Diagnostics.Modules,
+        description: Diagnostics.Check_side_effect_imports,
+        defaultValueDescription: false,
+    },
 
     // Source Maps
     {

src/compiler/diagnosticMessages.json

@@ -6388,6 +6388,10 @@
         "category": "Message",
         "code": 6805
     },
+    "Check side effect imports.": {
+        "category": "Message",
+        "code": 6806
+    },
 
     "one of:": {
         "category": "Message",

src/compiler/types.ts

@@ -7418,6 +7418,7 @@ export interface CompilerOptions {
     target?: ScriptTarget;
     traceResolution?: boolean;
     useUnknownInCatchVariables?: boolean;
+    noUncheckedSideEffectImports?: boolean;
     resolveJsonModule?: boolean;
     types?: string[];
     /** Paths used to compute primary types search locations */

src/compiler/utilities.ts

@@ -287,6 +287,7 @@ import {
     isIdentifier,
     isIdentifierStart,
     isIdentifierText,
+    isImportDeclaration,
     isImportTypeNode,
     isInterfaceDeclaration,
     isJSDoc,
@@ -11758,3 +11759,9 @@ export function hasInferredType(node: Node): node is HasInferredType {
             return false;
     }
 }
+
+/** @internal */
+export function isSideEffectImport(node: Node): boolean {
+    const ancestor = findAncestor(node, isImportDeclaration);
+    return !!ancestor && !ancestor.importClause;
+}

src/testRunner/unittests/tscWatch/programUpdates.ts

@@ -2245,4 +2245,40 @@ import { x } from "../b";`,
             },
         ],
     });
+
+    verifyTscWatch({
+        scenario,
+        subScenario: "when changing noUncheckedSideEffectImports of config file",
+        commandLineArgs: ["-w", "-p", ".", "--extendedDiagnostics"],
+        sys: () => {
+            const module1: File = {
+                path: `/user/username/projects/myproject/a.ts`,
+                content: `import "does-not-exist";`,
+            };
+            const config: File = {
+                path: `/user/username/projects/myproject/tsconfig.json`,
+                content: jsonToReadableText({
+                    compilerOptions: {
+                        noUncheckedSideEffectImports: false,
+                    },
+                }),
+            };
+            return createWatchedSystem([module1, config, libFile], { currentDirectory: "/user/username/projects/myproject" });
+        },
+        edits: [
+            {
+                caption: "Change noUncheckedSideEffectImports to true",
+                edit: sys =>
+                    sys.writeFile(
+                        `/user/username/projects/myproject/tsconfig.json`,
+                        jsonToReadableText({
+                            compilerOptions: {
+                                noUncheckedSideEffectImports: true,
+                            },
+                        }),
+                    ),
+                timeouts: sys => sys.runQueuedTimeoutCallbacks(),
+            },
+        ],
+    });
 });