From 4a5618e60cdaf5664f269380235db48ef4550fac Mon Sep 17 00:00:00 2001
From: Ivan Goncharov <ivan.goncharov.ua@gmail.com>
Date: Tue, 21 May 2019 12:12:28 +0300
Subject: [PATCH] Enable "sketchy-null-mixed" Flow check

---
 .flowconfig                            | 2 +-
 src/error/GraphQLError.js              | 8 +++++++-
 src/jsutils/inspect.js                 | 2 +-
 src/jsutils/invariant.js               | 3 ++-
 src/language/__tests__/toJSONDeep.js   | 2 +-
 src/language/__tests__/visitor-test.js | 4 ++--
 6 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/.flowconfig b/.flowconfig
index 75fcf47dbe..c7d484ac4c 100644
--- a/.flowconfig
+++ b/.flowconfig
@@ -13,7 +13,7 @@
 sketchy-null-bool=off
 sketchy-null-string=off
 sketchy-null-number=error
-sketchy-null-mixed=off
+sketchy-null-mixed=error
 sketchy-number=error
 untyped-type-import=error
 nonstrict-import=off
diff --git a/src/error/GraphQLError.js b/src/error/GraphQLError.js
index c25c964f95..175eb72b01 100644
--- a/src/error/GraphQLError.js
+++ b/src/error/GraphQLError.js
@@ -138,7 +138,13 @@ export function GraphQLError( // eslint-disable-line no-redeclare
     }, []);
   }
 
-  const _extensions = extensions || (originalError && originalError.extensions);
+  let _extensions = extensions;
+  if (_extensions == null && originalError != null) {
+    const originalExtensions = originalError.extensions;
+    if (originalExtensions != null && typeof originalExtensions === 'object') {
+      _extensions = originalExtensions;
+    }
+  }
 
   Object.defineProperties(this, {
     message: {
diff --git a/src/jsutils/inspect.js b/src/jsutils/inspect.js
index e277dd1504..c5642b4d03 100644
--- a/src/jsutils/inspect.js
+++ b/src/jsutils/inspect.js
@@ -41,7 +41,7 @@ function formatObjectValue(value, previouslySeenValues) {
   if (value) {
     const customInspectFn = getCustomFn(value);
 
-    if (customInspectFn) {
+    if (customInspectFn !== undefined) {
       // $FlowFixMe(>=0.90.0)
       const customValue = customInspectFn.call(value);
 
diff --git a/src/jsutils/invariant.js b/src/jsutils/invariant.js
index a3cf0daf38..350cff5b86 100644
--- a/src/jsutils/invariant.js
+++ b/src/jsutils/invariant.js
@@ -8,8 +8,9 @@
  */
 
 export default function invariant(condition: mixed, message: string) {
+  const booleanCondition = Boolean(condition);
   /* istanbul ignore else */
-  if (!condition) {
+  if (!booleanCondition) {
     throw new Error(message);
   }
 }
diff --git a/src/language/__tests__/toJSONDeep.js b/src/language/__tests__/toJSONDeep.js
index 6b22e842ee..4b0c3042f7 100644
--- a/src/language/__tests__/toJSONDeep.js
+++ b/src/language/__tests__/toJSONDeep.js
@@ -12,7 +12,7 @@
  * on any nested value which defines it.
  */
 export default function toJSONDeep<T>(value: T): T {
-  if (!value || typeof value !== 'object') {
+  if (value == null || typeof value !== 'object') {
     return value;
   }
 
diff --git a/src/language/__tests__/visitor-test.js b/src/language/__tests__/visitor-test.js
index 2bbca5dc33..f14eaf8d91 100644
--- a/src/language/__tests__/visitor-test.js
+++ b/src/language/__tests__/visitor-test.js
@@ -472,7 +472,7 @@ describe('Visitor', () => {
           'enter',
           node.kind,
           key,
-          parent && parent.kind ? parent.kind : undefined,
+          parent && parent.kind != null ? parent.kind : undefined,
         ]);
 
         checkVisitorFnArgs(ast, arguments);
@@ -484,7 +484,7 @@ describe('Visitor', () => {
           'leave',
           node.kind,
           key,
-          parent && parent.kind ? parent.kind : undefined,
+          parent && parent.kind != null ? parent.kind : undefined,
         ]);
 
         expect(argsStack.pop()).to.deep.equal([...arguments]);