From 1959de4ea6e1cdacfac215f2773b4d2cef2d2ccb Mon Sep 17 00:00:00 2001
From: Evgeny Poberezkin <2769109+epoberezkin@users.noreply.github.com>
Date: Tue, 16 Nov 2021 20:04:31 +0000
Subject: [PATCH] fix minContains: 0, closes #1819 (#1820)

---
 lib/vocabularies/applicator/contains.ts |  9 ++++-----
 spec/issues/1819_mincontains.spec.ts    | 19 +++++++++++++++++++
 2 files changed, 23 insertions(+), 5 deletions(-)
 create mode 100644 spec/issues/1819_mincontains.spec.ts

diff --git a/lib/vocabularies/applicator/contains.ts b/lib/vocabularies/applicator/contains.ts
index 0c398d1d6..d88675c6c 100644
--- a/lib/vocabularies/applicator/contains.ts
+++ b/lib/vocabularies/applicator/contains.ts
@@ -63,13 +63,12 @@ const def: CodeKeywordDefinition = {
     const valid = gen.name("valid")
     if (max === undefined && min === 1) {
       validateItems(valid, () => gen.if(valid, () => gen.break()))
+    } else if (min === 0) {
+      gen.let(valid, true)
+      if (max !== undefined) gen.if(_`${data}.length > 0`, validateItemsWithCount)
     } else {
       gen.let(valid, false)
-      if (min === 0) {
-        gen.if(_`${data}.length > 0`, validateItemsWithCount, () => gen.assign(valid, true))
-      } else {
-        validateItemsWithCount()
-      }
+      validateItemsWithCount()
     }
     cxt.result(valid, () => cxt.reset())
 
diff --git a/spec/issues/1819_mincontains.spec.ts b/spec/issues/1819_mincontains.spec.ts
new file mode 100644
index 000000000..3fc454d77
--- /dev/null
+++ b/spec/issues/1819_mincontains.spec.ts
@@ -0,0 +1,19 @@
+import _Ajv from "../ajv2020"
+import * as assert from "assert"
+
+describe("`minContains: 0` without valid items (issue #1819)", () => {
+  const ajv = new _Ajv()
+
+  const schema = {
+    type: "array",
+    minContains: 0,
+    maxContains: 1,
+    contains: {type: "number"},
+  }
+
+  const validate = ajv.compile(schema)
+
+  it("no items valid", () => assert.strictEqual(validate(["foo"]), true))
+  it("1 item valid", () => assert.strictEqual(validate(["foo", 1]), true))
+  it("2 items invalid", () => assert.strictEqual(validate(["foo", 1, 2]), false))
+})