From 97256855aceb63d74cf80dfa16c9c3af713e64b8 Mon Sep 17 00:00:00 2001
From: ssube <seansube@gmail.com>
Date: Sat, 2 Nov 2019 11:33:40 -0500
Subject: [PATCH] fix(visitor): handle missing errors gracefully

---
 src/rule/index.ts  |  2 +-
 src/utils/index.ts | 11 ++++++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/rule/index.ts b/src/rule/index.ts
index 1c9dbee..ab5f7ec 100644
--- a/src/rule/index.ts
+++ b/src/rule/index.ts
@@ -189,7 +189,7 @@ export async function visitRules(ctx: VisitorContext, rules: Array<SchemaRule>,
       const itemResult = cloneDeep(item);
       const ruleResult = await rule.visit(ctx, itemResult);
 
-      if (ruleResult.errors.length > 0) {
+      if (hasItems(ruleResult.errors)) {
         ctx.logger.warn({ count: ruleResult.errors.length, rule }, 'rule failed');
         ctx.mergeResult(ruleResult);
         continue;
diff --git a/src/utils/index.ts b/src/utils/index.ts
index 4e80cf0..dcf0d31 100644
--- a/src/utils/index.ts
+++ b/src/utils/index.ts
@@ -4,7 +4,16 @@ export function doesExist<T>(val: T | null | undefined): val is T {
   return !isNil(val);
 }
 
-export function hasItems<T>(val: Array<T> | null | undefined): val is Array<T> {
+/**
+ * Test if a value is an array with some items (length > 0).
+ *
+ * This is not a general replacement for `.length > 0`, since it is also a typeguard:
+ * `if (hasItems(val)) else { val }` will complain that `val` is `never` in the `else`
+ * branch, since it was proven not to be an array by this function.
+ */
+export function hasItems<T>(val: Array<T> | null | undefined): val is Array<T>;
+export function hasItems<T>(val: ReadonlyArray<T> | null | undefined): val is ReadonlyArray<T>;
+export function hasItems<T>(val: ReadonlyArray<T> | null | undefined): val is ReadonlyArray<T> {
   return (Array.isArray(val) && val.length > 0);
 }