Intercept SyntaxError exception in evaluator to diagnose errors in output

Author: rbuckton

Diff for: src/harness/evaluatorImpl.ts

@@ -168,9 +168,17 @@ namespace evaluator {
             const base = vpath.dirname(file);
             const localRequire = (id: string) => this.import(id, base);
             const evaluateText = `(function (module, exports, require, __dirname, __filename, ${globalNames.join(", ")}) { ${text} })`;
-            // eslint-disable-next-line no-eval
-            const evaluateThunk = (void 0, eval)(evaluateText) as (module: any, exports: any, require: (id: string) => any, dirname: string, filename: string, ...globalArgs: any[]) => void;
-            evaluateThunk.call(this.globals, module, module.exports, localRequire, vpath.dirname(file), file, ...globalArgs);
+            try {
+                // eslint-disable-next-line no-eval
+                const evaluateThunk = (void 0, eval)(evaluateText) as (module: any, exports: any, require: (id: string) => any, dirname: string, filename: string, ...globalArgs: any[]) => void;
+                evaluateThunk.call(this.globals, module, module.exports, localRequire, vpath.dirname(file), file, ...globalArgs);
+            }
+            catch (e) {
+                if (e instanceof SyntaxError) {
+                    throw new Error(`Evaluation failed: ${e.message}\nSource text:\n\n${evaluateText.split(/\r?\n/g).map(s => `  ${s}`).join("\n")}`);
+                }
+                throw e;
+            }
         }
     }