Merge pull request #30776 from andrewbranch/feature/10178

Add flag to allow access to UMD globals from modules

src/compiler/checker.ts

@@ -1648,7 +1648,7 @@ namespace ts {
                 if (result && isInExternalModule && (meaning & SymbolFlags.Value) === SymbolFlags.Value && !(originalLocation!.flags & NodeFlags.JSDoc)) {
                     const merged = getMergedSymbol(result);
                     if (length(merged.declarations) && every(merged.declarations, d => isNamespaceExportDeclaration(d) || isSourceFile(d) && !!d.symbol.globalExports)) {
-                        error(errorLocation!, Diagnostics._0_refers_to_a_UMD_global_but_the_current_file_is_a_module_Consider_adding_an_import_instead, unescapeLeadingUnderscores(name)); // TODO: GH#18217
+                        errorOrSuggestion(!compilerOptions.allowUmdGlobalAccess, errorLocation!, Diagnostics._0_refers_to_a_UMD_global_but_the_current_file_is_a_module_Consider_adding_an_import_instead, unescapeLeadingUnderscores(name));
                     }
                 }
             }

src/compiler/commandLineParser.ts

@@ -588,6 +588,13 @@ namespace ts {
             category: Diagnostics.Module_Resolution_Options,
             description: Diagnostics.Do_not_resolve_the_real_path_of_symlinks,
         },
+        {
+            name: "allowUmdGlobalAccess",
+            type: "boolean",
+            affectsSemanticDiagnostics: true,
+            category: Diagnostics.Module_Resolution_Options,
+            description: Diagnostics.Allow_accessing_UMD_globals_from_modules,
+        },
 
         // Source Maps
         {

src/compiler/diagnosticMessages.json

@@ -4946,5 +4946,9 @@
     "Convert parameters to destructured object": {
         "category": "Message",
         "code": 95075
+    },
+    "Allow accessing UMD globals from modules.": {
+        "category": "Message",
+        "code": 95076
     }
 }

src/compiler/types.ts

@@ -4589,6 +4589,7 @@ namespace ts {
         allowJs?: boolean;
         /*@internal*/ allowNonTsExtensions?: boolean;
         allowSyntheticDefaultImports?: boolean;
+        allowUmdGlobalAccess?: boolean;
         allowUnreachableCode?: boolean;
         allowUnusedLabels?: boolean;
         alwaysStrict?: boolean;  // Always combine with strict property