Fix bug: Return a resolution diagnostic for a .jsx import if --allowJs is turned off

Author: Andy Hanson

src/compiler/program.ts

@@ -1580,13 +1580,19 @@ namespace ts {
             case Extension.Dts:
                 // These are always allowed.
                 return undefined;
-
             case Extension.Tsx:
+                return needJsx();
             case Extension.Jsx:
-                return options.jsx ? undefined : Diagnostics.Module_0_was_resolved_to_1_but_jsx_is_not_set;
-
+                return needJsx() || needAllowJs();
             case Extension.Js:
-                return options.allowJs ? undefined : Diagnostics.Module_0_was_resolved_to_1_but_allowJs_is_not_set;
+                return needAllowJs();
+        }
+
+        function needJsx() {
+            return options.jsx ? undefined : Diagnostics.Module_0_was_resolved_to_1_but_jsx_is_not_set;
+        }
+        function needAllowJs() {
+            return options.allowJs ? undefined : Diagnostics.Module_0_was_resolved_to_1_but_allowJs_is_not_set;
         }
     }
 }

tests/baselines/reference/moduleResolutionWithExtensions_notSupported3.errors.txt

@@ -0,0 +1,12 @@
+/a.ts(1,17): error TS6143: Module './jsx' was resolved to '/jsx.jsx', but '--allowJs' is not set.
+
+
+==== /a.ts (1 errors) ====
+    import jsx from "./jsx";
+                    ~~~~~~~
+!!! error TS6143: Module './jsx' was resolved to '/jsx.jsx', but '--allowJs' is not set.
+    
+==== /jsx.jsx (0 errors) ====
+    // Test the error message if we have `--jsx` but not `--allowJw`.
+    
+    

tests/baselines/reference/moduleResolutionWithExtensions_notSupported3.js

@@ -0,0 +1,12 @@
+//// [tests/cases/compiler/moduleResolutionWithExtensions_notSupported3.ts] ////
+
+//// [jsx.jsx]
+// Test the error message if we have `--jsx` but not `--allowJw`.
+
+
+//// [a.ts]
+import jsx from "./jsx";
+
+
+//// [a.js]
+"use strict";

tests/baselines/reference/moduleResolutionWithExtensions_notSupported3.trace.json

@@ -0,0 +1,17 @@
+[
+    "======== Resolving module './jsx' from '/a.ts'. ========",
+    "Module resolution kind is not specified, using 'NodeJs'.",
+    "Loading module as file / folder, candidate module location '/jsx'.",
+    "File '/jsx.ts' does not exist.",
+    "File '/jsx.tsx' does not exist.",
+    "File '/jsx.d.ts' does not exist.",
+    "File '/jsx/package.json' does not exist.",
+    "File '/jsx/index.ts' does not exist.",
+    "File '/jsx/index.tsx' does not exist.",
+    "File '/jsx/index.d.ts' does not exist.",
+    "Loading module as file / folder, candidate module location '/jsx'.",
+    "File '/jsx.js' does not exist.",
+    "File '/jsx.jsx' exist - use it as a name resolution result.",
+    "Resolving real path for '/jsx.jsx', result '/jsx.jsx'",
+    "======== Module name './jsx' was successfully resolved to '/jsx.jsx'. ========"
+]

tests/cases/compiler/moduleResolutionWithExtensions_notSupported3.ts

@@ -0,0 +1,9 @@
+// @noImplicitReferences: true
+// @jsx: preserve
+// @traceResolution: true
+// Test the error message if we have `--jsx` but not `--allowJw`.
+
+// @Filename: /jsx.jsx
+
+// @Filename: /a.ts
+import jsx from "./jsx";