feat(ui): pretty JSON rendering tool outputs (#9767)

Co-authored-by: Bryan Morgan <bryanmorgan@google.com>

packages/cli/src/utils/jsonoutput.test.ts

@@ -0,0 +1,100 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import { checkInput, tryParseJSON } from './jsonoutput.js';
+
+describe('check tools output', () => {
+  it('accepts object-like JSON strings', () => {
+    const testJSON = '{"a":1, "b": 2}';
+    expect(checkInput(testJSON)).toBeTruthy();
+  });
+
+  it('accepts array JSON strings', () => {
+    expect(checkInput('[1,2,3]')).toBeTruthy();
+  });
+
+  it('rejects primitive strings/plaintext strings', () => {
+    expect(checkInput('test text')).toBeFalsy();
+  });
+
+  it('rejects empty strings', () => {
+    expect(checkInput('')).toBeFalsy();
+  });
+
+  it('rejects null and undefined', () => {
+    expect(checkInput(null)).toBeFalsy();
+    expect(checkInput(undefined)).toBeFalsy();
+  });
+
+  it('rejects malformed JSON-like strings', () => {
+    const malformedJSON = '"a":1,}';
+
+    expect(checkInput(malformedJSON)).toBeFalsy();
+  });
+
+  it('rejects mixed text and JSON text strings', () => {
+    const testJSON = 'text {"a":1, "b": 2}';
+    expect(checkInput(testJSON)).toBeFalsy();
+  });
+
+  it('rejects ANSI-tainted input', () => {
+    const text = '\u001B[32m{"a":1}\u001B[0m';
+
+    expect(checkInput(text)).toBeFalsy();
+  });
+});
+
+describe('check parsing json', () => {
+  it('returns parsed object for valid JSON', () => {
+    const testJSON = '{"a":1, "b": 2}';
+    const parsedTestJSON = JSON.parse(testJSON);
+
+    const output = tryParseJSON(testJSON);
+
+    expect(output).toEqual(parsedTestJSON);
+  });
+
+  it('returns parsed array for non-empty arrays', () => {
+    const testJSON = '[1,2,3]';
+    const parsedTestJSON = JSON.parse(testJSON);
+
+    const output = tryParseJSON(testJSON);
+
+    expect(output).toEqual(parsedTestJSON);
+  });
+
+  it('returns null for Malformed JSON', () => {
+    const text = '{"a":1,}';
+
+    expect(tryParseJSON(text)).toBeFalsy();
+  });
+
+  it('returns null for empty arrays', () => {
+    const testArr = '[]';
+
+    expect(tryParseJSON(testArr)).toBeFalsy();
+  });
+
+  it('returns null for empty objects', () => {
+    const testObj = '{}';
+
+    expect(tryParseJSON(testObj)).toBeFalsy();
+  });
+
+  it('trims whitespace and parse valid json', () => {
+    const text = '\n  { "a": 1 }  \n';
+    expect(tryParseJSON(text)).toBeTruthy();
+  });
+
+  it('returns null for plaintext', () => {
+    const testText = 'test plaintext';
+
+    const output = tryParseJSON(testText);
+
+    expect(output).toBeFalsy();
+  });
+});

packages/cli/src/utils/jsonoutput.ts

@@ -0,0 +1,46 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import stripAnsi from 'strip-ansi';
+
+export function checkInput(input: string | null | undefined): boolean {
+  if (input === null || input === undefined) {
+    return false;
+  }
+
+  const trimmed = input.trim();
+  if (!trimmed) {
+    return false;
+  }
+
+  if (!/^(?:\[|\{)/.test(trimmed)) {
+    return false;
+  }
+
+  if (stripAnsi(trimmed) !== trimmed) return false;
+
+  return true;
+}
+
+export function tryParseJSON(input: string): object | null {
+  if (!checkInput(input)) return null;
+  const trimmed = input.trim();
+  try {
+    const parsed = JSON.parse(trimmed);
+    if (parsed === null || typeof parsed !== 'object') {
+      return null;
+    }
+    if (Array.isArray(parsed) && parsed.length === 0) {
+      return null;
+    }
+
+    if (!Array.isArray(parsed) && Object.keys(parsed).length === 0) return null;
+
+    return parsed;
+  } catch (_err) {
+    return null;
+  }
+}