test(json): improve json testing (#5075)

json/_common.ts

@@ -5,14 +5,11 @@ import type { JsonValue } from "./common.ts";
 export function parse(text: string): JsonValue {
   try {
     return JSON.parse(text);
-  } catch (error: unknown) {
-    if (error instanceof Error) {
-      // Truncate the string so that it is within 30 lengths.
-      const truncatedText = 30 < text.length ? `${text.slice(0, 30)}...` : text;
-      throw new (error.constructor as ErrorConstructor)(
-        `${error.message} (parsing: '${truncatedText}')`,
-      );
-    }
-    throw error;
+  } catch (error) {
+    // Truncate the string so that it is within 30 lengths.
+    const truncatedText = 30 < text.length ? `${text.slice(0, 30)}...` : text;
+    throw new ((error as Error).constructor as ErrorConstructor)(
+      `${(error as Error).message} (parsing: '${truncatedText}')`,
+    );
   }
 }

json/concatenated_json_parse_stream_test.ts

@@ -268,6 +268,14 @@ Deno.test({
       ["tr", 'ue{"foo": "bar"}'],
       [true, { foo: "bar" }],
     );
+    // Invalid primitive which share some leading characters with the valid primitive
+    await assertInvalidParse(
+      ConcatenatedJsonParseStream,
+      ["truu"],
+      {},
+      SyntaxError,
+      `Unexpected token 'u', \"truu\" is not valid JSON (parsing: 'truu')`,
+    );
   },
 });