diff --git a/packages/plugin-ext/src/plugin/type-converters.spec.ts b/packages/plugin-ext/src/plugin/type-converters.spec.ts
index a76b3de3fa7f2..2130d6e342cc5 100644
--- a/packages/plugin-ext/src/plugin/type-converters.spec.ts
+++ b/packages/plugin-ext/src/plugin/type-converters.spec.ts
@@ -437,4 +437,24 @@ describe('Type converters:', () => {
             assert.deepStrictEqual(result, showOptions);
         });
     });
+
+    describe('#convertCode', () => {
+        it('should convert a "code" of type "string"', () => {
+            assert.strictEqual(Converter.convertCode('string'), 'string');
+        });
+        it('should convert a "code" of type "number"', () => {
+            assert.strictEqual(Converter.convertCode(4), '4');
+        });
+        it('should convert an undefined "code"', () => {
+            assert.strictEqual(Converter.convertCode(undefined), undefined);
+        });
+        it('should convert a "code" of type "{ value: number, target: Uri }"', () => {
+            const uri = types.URI.parse('foo://example.com:8042/over/there?name=ferret#nose');
+            assert.strictEqual(Converter.convertCode({ value: 4, target: uri }), '4');
+        });
+        it('should convert a "code" of type "{ value: number, target: Uri }"', () => {
+            const uri = types.URI.parse('foo://example.com:8042/over/there?name=ferret#nose');
+            assert.strictEqual(Converter.convertCode({ value: 'string', target: uri }), 'string');
+        });
+    });
 });
diff --git a/packages/plugin-ext/src/plugin/type-converters.ts b/packages/plugin-ext/src/plugin/type-converters.ts
index 4b80b2b11a2f9..116ec4fbb959b 100644
--- a/packages/plugin-ext/src/plugin/type-converters.ts
+++ b/packages/plugin-ext/src/plugin/type-converters.ts
@@ -332,12 +332,15 @@ export function convertDiagnosticToMarkerData(diagnostic: theia.Diagnostic): mod
     };
 }
 
-function convertCode(code: string | number | undefined): string | undefined {
+export function convertCode(code: string | number | { value: string | number; target: theia.Uri } | undefined): string | undefined {
     if (typeof code === 'number') {
         return String(code);
-    } else {
-        return code;
     }
+    if (typeof code === 'string' || typeof code === 'undefined') {
+        return code;
+    } else {
+        return String(code.value);
+    };
 }
 
 function convertSeverity(severity: types.DiagnosticSeverity): types.MarkerSeverity {
diff --git a/packages/plugin/src/theia.d.ts b/packages/plugin/src/theia.d.ts
index e40bce79c6793..725d19f0c95c7 100644
--- a/packages/plugin/src/theia.d.ts
+++ b/packages/plugin/src/theia.d.ts
@@ -8233,11 +8233,21 @@ export module '@theia/plugin' {
         source?: string;
 
         /**
-         * A code or identifier for this diagnostics. Will not be surfaced
-         * to the user, but should be used for later processing, e.g. when
-         * providing {@link CodeActionContext code actions}.
+         * A code or identifier for this diagnostic.
+         * Should be used for later processing, e.g. when providing {@link CodeActionContext code actions}.
          */
-        code?: string | number;
+        code?: string | number | {
+            /**
+             * A code or identifier for this diagnostic.
+             * Should be used for later processing, e.g. when providing {@link CodeActionContext code actions}.
+             */
+            value: string | number;
+
+            /**
+             * A target URI to open with more information about the diagnostic error.
+             */
+            target: Uri;
+        };
 
         /**
          * An array of related diagnostic information, e.g. when symbol-names within