inspect: Correctly handle custom inspect returning this

src/jsutils/__tests__/inspect-test.js

@@ -96,6 +96,16 @@ describe('inspect', () => {
     expect(inspect(object)).to.equal('<custom inspect>');
   });
 
+  it('custom inspect that return `this` should work', () => {
+    const object = {
+      inspect() {
+        return this;
+      },
+    };
+
+    expect(inspect(object)).to.equal('{ inspect: [function inspect] }');
+  });
+
   it('custom symbol inspect is take precedence', () => {
     invariant(nodejsCustomInspectSymbol);
 

src/jsutils/inspect.js

@@ -32,9 +32,13 @@ function formatValue(value, recurseTimes) {
         if (customInspectFn) {
           // $FlowFixMe(>=0.90.0)
           const customValue = customInspectFn.call(value);
-          return typeof customValue === 'string'
-            ? customValue
-            : formatValue(customValue, recurseTimes);
+
+          // check for infinite recursion
+          if (customValue !== value) {
+            return typeof customValue === 'string'
+              ? customValue
+              : formatValue(customValue, recurseTimes);
+          }
         } else if (Array.isArray(value)) {
           return formatArray(value, recurseTimes);
         }