inspect: Limit maximum depth of printed objects

Author: IvanGoncharov

src/jsutils/__tests__/inspect-test.js

@@ -55,6 +55,9 @@ describe('inspect', () => {
     expect(inspect([1, NaN])).to.equal('[1, NaN]');
     expect(inspect([['a', 'b'], 'c'])).to.equal('[["a", "b"], "c"]');
 
+    expect(inspect([[[]]])).to.equal('[[[]]]');
+    expect(inspect([[['a']]])).to.equal('[[[Array]]]');
+
     expect(inspect([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])).to.equal(
       '[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]',
     );
@@ -74,6 +77,9 @@ describe('inspect', () => {
     expect(inspect({ a: 1, b: 2 })).to.equal('{ a: 1, b: 2 }');
     expect(inspect({ array: [null, 0] })).to.equal('{ array: [null, 0] }');
 
+    expect(inspect({ a: { b: {} } })).to.equal('{ a: { b: {} } }');
+    expect(inspect({ a: { b: { c: 1 } } })).to.equal('{ a: { b: [Object] } }');
+
     const map = Object.create(null);
     map['a'] = true;
     map['b'] = null;
@@ -125,4 +131,19 @@ describe('inspect', () => {
 
     expect(inspect(object)).to.equal('Hello World!');
   });
+
+  it('Use class names for the shortform of an object', () => {
+    class Foo {
+      foo: string;
+
+      constructor() {
+        this.foo = 'bar';
+      }
+    }
+
+    expect(inspect([[new Foo()]])).to.equal('[[[Foo]]]');
+
+    (Foo.prototype: any)[Symbol.toStringTag] = 'Bar';
+    expect(inspect([[new Foo()]])).to.equal('[[[Bar]]]');
+  });
 });

src/jsutils/inspect.js

@@ -10,15 +10,16 @@
 import nodejsCustomInspectSymbol from './nodejsCustomInspectSymbol';
 
 const MAX_ARRAY_LENGTH = 10;
+const MAX_RECURSIVE_DEPTH = 2;
 
 /**
  * Used to print values in error messages.
  */
 export default function inspect(value: mixed): string {
-  return formatValue(value);
+  return formatValue(value, 0);
 }
 
-function formatValue(value) {
+function formatValue(value, recurseTimes) {
   switch (typeof value) {
     case 'string':
       return JSON.stringify(value);
@@ -33,12 +34,12 @@ function formatValue(value) {
           const customValue = customInspectFn.call(value);
           return typeof customValue === 'string'
             ? customValue
-            : formatValue(customValue);
+            : formatValue(customValue, recurseTimes);
         } else if (Array.isArray(value)) {
-          return formatArray(value);
+          return formatArray(value, recurseTimes);
         }
 
-        return formatObject(value);
+        return formatObject(value, recurseTimes);
       }
 
       return String(value);
@@ -47,31 +48,39 @@ function formatValue(value) {
   }
 }
 
-function formatObject(object) {
+function formatObject(object, recurseTimes) {
   const keys = Object.keys(object);
   if (keys.length === 0) {
     return '{}';
   }
 
+  if (recurseTimes === MAX_RECURSIVE_DEPTH) {
+    return '[' + getObjectTag(object) + ']';
+  }
+
   const properties = keys.map(key => {
-    const value = formatValue(object[key]);
+    const value = formatValue(object[key], recurseTimes + 1);
     return key + ': ' + value;
   });
 
   return '{ ' + properties.join(', ') + ' }';
 }
 
-function formatArray(array) {
+function formatArray(array, recurseTimes) {
   if (array.length === 0) {
     return '[]';
   }
 
+  if (recurseTimes === MAX_RECURSIVE_DEPTH) {
+    return '[Array]';
+  }
+
   const len = Math.min(MAX_ARRAY_LENGTH, array.length);
   const remaining = array.length - len;
   const items = [];
 
   for (let i = 0; i < len; ++i) {
-    items.push(formatValue(array[i]));
+    items.push(formatValue(array[i], recurseTimes + 1));
   }
 
   if (remaining === 1) {
@@ -94,3 +103,19 @@ function getCustomFn(object) {
     return object.inspect;
   }
 }
+
+function getObjectTag(object) {
+  const tag = Object.prototype.toString
+    .call(object)
+    .replace(/^\[object /, '')
+    .replace(/]$/, '');
+
+  if (tag === 'Object' && typeof object.constructor === 'function') {
+    const name = object.constructor.name;
+    if (typeof name === 'string') {
+      return name;
+    }
+  }
+
+  return tag;
+}