Don’t remove imports that are used for module augmentation, just remove their import clauses

Author: andrewbranch

src/services/organizeImports.ts

@@ -89,7 +89,7 @@ namespace ts.OrganizeImports {
         const usedImports: ImportDeclaration[] = [];
 
         for (const importDecl of oldImports) {
-            const {importClause} = importDecl;
+            const { importClause, moduleSpecifier } = importDecl;
 
             if (!importClause) {
                 // Imports without import clauses are assumed to be included for their side effects and are not removed.
@@ -125,6 +125,14 @@ namespace ts.OrganizeImports {
             if (name || namedBindings) {
                 usedImports.push(updateImportDeclarationAndClause(importDecl, name, namedBindings));
             }
+            // If a module is imported to be augmented, keep the import declaration, but without an import clause
+            else if (hasModuleDeclarationMatchingSpecifier(sourceFile, moduleSpecifier)) {
+                usedImports.push(createImportDeclaration(
+                    importDecl.decorators,
+                    importDecl.modifiers,
+                    /*importClause*/ undefined,
+                    moduleSpecifier));
+            }
         }
 
         return usedImports;
@@ -135,6 +143,14 @@ namespace ts.OrganizeImports {
         }
     }
 
+    function hasModuleDeclarationMatchingSpecifier(sourceFile: SourceFile, moduleSpecifier: Expression) {
+        const moduleSpecifierText = isStringLiteral(moduleSpecifier) && moduleSpecifier.text;
+        return isString(moduleSpecifierText) && some(sourceFile.statements, statement =>
+            isModuleDeclaration(statement)
+            && isStringLiteral(statement.name)
+            && statement.name.text === moduleSpecifierText);
+    }
+
     function getExternalModuleName(specifier: Expression) {
         return specifier !== undefined && isStringLiteralLike(specifier)
             ? specifier.text

src/testRunner/unittests/services/organizeImports.ts

@@ -1,5 +1,5 @@
 namespace ts {
-    describe("unittests:: services:: Organize imports", () => {
+    describe("unittests:: services:: organizeImports", () => {
         describe("Sort imports", () => {
             it("Sort - non-relative vs non-relative", () => {
                 assertSortsBefore(
@@ -347,8 +347,10 @@ import { } from "lib";
             {
                 path: "/test.d.ts",
                 content: `
+import foo from 'foo';
 import { Caseless } from 'caseless';
 
+declare module 'foo' {}
 declare module 'caseless' {
     interface Caseless {
         test(name: KeyType): boolean;

tests/baselines/reference/organizeImports/Unused_false_positive_module_augmentation.ts

@@ -0,0 +1,22 @@
+// ==ORIGINAL==
+
+import foo from 'foo';
+import { Caseless } from 'caseless';
+
+declare module 'foo' {}
+declare module 'caseless' {
+    interface Caseless {
+        test(name: KeyType): boolean;
+    }
+}
+// ==ORGANIZED==
+
+import 'caseless';
+import 'foo';
+
+declare module 'foo' {}
+declare module 'caseless' {
+    interface Caseless {
+        test(name: KeyType): boolean;
+    }
+}