Don’t show auto-import suggestion if there’s a global by the same name

src/harness/fourslash.ts

@@ -782,7 +782,7 @@ namespace FourSlash {
                         const name = typeof include === "string" ? include : include.name;
                         const found = nameToEntries.get(name);
                         if (!found) throw this.raiseError(`No completion ${name} found`);
-                        assert(found.length === 1); // Must use 'exact' for multiple completions with same name
+                        assert(found.length === 1, `Multiple completions named '${name}' were found. Using 'exact' is required.`);
                         this.verifyCompletionEntry(ts.first(found), include);
                     }
                 }

src/services/completions.ts

@@ -273,6 +273,7 @@ namespace ts.Completions {
         // Based on the order we add things we will always see locals first, then globals, then module exports.
         // So adding a completion for a local will prevent us from adding completions for external module exports sharing the same name.
         const uniques = createMap<true>();
+        const uniqueGlobals = createMap<true>();
         for (const symbol of symbols) {
             const origin = symbolToOriginInfoMap ? symbolToOriginInfoMap[getSymbolId(symbol)] : undefined;
             const entry = createCompletionEntry(symbol, location, sourceFile, typeChecker, target, kind, origin, recommendedCompletion, propertyAccessToConvert, isJsxInitializer, preferences);
@@ -285,12 +286,20 @@ namespace ts.Completions {
                 continue;
             }
 
-            // Latter case tests whether this is a global variable.
-            if (!origin && !(symbol.parent === undefined && !some(symbol.declarations, d => d.getSourceFile() === location!.getSourceFile()))) { // TODO: GH#18217
+            const isExternalModule = !!origin;
+            const isTopLevel = symbol.parent === undefined;
+            const hasDeclarationInFile = some(symbol.declarations, d => d.getSourceFile() === location!.getSourceFile());
+            if (!isExternalModule && !(isTopLevel && !hasDeclarationInFile)) {
                 uniques.set(name, true);
             }
+            else if (isTopLevel && !isExternalModule && !hasDeclarationInFile) {
+                uniqueGlobals.set(name, true);
+            }
 
-            entries.push(entry);
+            const shouldBeShadowedByGlobal = isExternalModule && uniqueGlobals.has(name);
+            if (!shouldBeShadowedByGlobal) {
+                entries.push(entry);
+            }
         }
 
         log("getCompletionsAtPosition: getCompletionEntriesFromSymbols: " + (timestamp() - start));

tests/cases/fourslash/completionsImport_multipleWithSameName.ts

@@ -3,10 +3,6 @@
 // @module: esnext
 // @noLib: true
 
-// @Filename: /global.d.ts
-// A local variable would prevent import completions (see `completionsImport_shadowedByLocal.ts`), but a global doesn't.
-////declare var foo: number;
-
 // @Filename: /a.ts
 ////export const foo = 0;
 
@@ -21,7 +17,6 @@ verify.completions({
     marker: "",
     exact: [
         "globalThis",
-        { name: "foo", text: "var foo: number", kind: "var", kindModifiers: "declare" },
         "undefined",
         {
             name: "foo",

tests/cases/fourslash/completionsImport_shadowedByGlobal.ts

@@ -0,0 +1,14 @@
+/// <reference path="fourslash.ts" />
+
+// @Filename: /a.ts
+//// export const parseInt = 0;
+
+// @Filename: /b.ts
+////parseI/**/
+
+verify.completions({
+  marker: "",
+  // The real parseInt is in 'globalVars', the fake one exported from a.ts is missing
+  exact: ["globalThis", ...completion.globalsVars, "undefined", ...completion.statementKeywordsWithTypes],
+  preferences: { includeCompletionsForModuleExports: true },
+});