From d33a36dab516bb65a6af408fc883f3ab935883d5 Mon Sep 17 00:00:00 2001
From: Jason Green <jasoniangreen@gmail.com>
Date: Sun, 4 Aug 2024 22:14:58 +0100
Subject: [PATCH] feat: add pattern and path to regexp create errors #2477

---
 lib/vocabularies/code.ts                      | 13 +++-
 lib/vocabularies/validation/pattern.ts        | 11 +++-
 .../2477_informative_pattern_errors.spec.ts   | 61 +++++++++++++++++++
 3 files changed, 80 insertions(+), 5 deletions(-)
 create mode 100644 spec/issues/2477_informative_pattern_errors.spec.ts

diff --git a/lib/vocabularies/code.ts b/lib/vocabularies/code.ts
index 92cdd5b04e..1710b4aa31 100644
--- a/lib/vocabularies/code.ts
+++ b/lib/vocabularies/code.ts
@@ -1,4 +1,4 @@
-import type {AnySchema, SchemaMap} from "../types"
+import type {AnySchema, RegExpLike, SchemaMap} from "../types"
 import type {SchemaCxt} from "../compile"
 import type {KeywordCxt} from "../compile/validate"
 import {CodeGen, _, and, or, not, nil, strConcat, getProperty, Code, Name} from "../compile/codegen"
@@ -92,10 +92,17 @@ export function callValidateCode(
 
 const newRegExp = _`new RegExp`
 
-export function usePattern({gen, it: {opts}}: KeywordCxt, pattern: string): Name {
+export function usePattern({gen, it: {opts, errSchemaPath}}: KeywordCxt, pattern: string): Name {
   const u = opts.unicodeRegExp ? "u" : ""
   const {regExp} = opts.code
-  const rx = regExp(pattern, u)
+
+  let rx: RegExpLike
+  try {
+    rx = new RegExp(pattern, u)
+  } catch (e) {
+    throw new Error(`Invalid regular expression: ${pattern} at ${errSchemaPath}`)
+  }
+  rx = regExp(pattern, u)
 
   return gen.scopeValue("pattern", {
     key: rx.toString(),
diff --git a/lib/vocabularies/validation/pattern.ts b/lib/vocabularies/validation/pattern.ts
index 7b27b7d3c0..947cd72ec6 100644
--- a/lib/vocabularies/validation/pattern.ts
+++ b/lib/vocabularies/validation/pattern.ts
@@ -18,9 +18,16 @@ const def: CodeKeywordDefinition = {
   error,
   code(cxt: KeywordCxt) {
     const {data, $data, schema, schemaCode, it} = cxt
-    // TODO regexp should be wrapped in try/catchs
     const u = it.opts.unicodeRegExp ? "u" : ""
-    const regExp = $data ? _`(new RegExp(${schemaCode}, ${u}))` : usePattern(cxt, schema)
+    const regExp = $data
+      ? _`(function() {
+        try {
+          return new RegExp(${schemaCode}, ${u})
+        } catch (e) {
+          throw new Error('Invalid regular expression: ' + ${schemaCode} + ' at ' + ${it.errSchemaPath})
+        }
+      })()`
+      : usePattern(cxt, schema)
     cxt.fail$data(_`!${regExp}.test(${data})`)
   },
 }
diff --git a/spec/issues/2477_informative_pattern_errors.spec.ts b/spec/issues/2477_informative_pattern_errors.spec.ts
new file mode 100644
index 0000000000..aa19ec4019
--- /dev/null
+++ b/spec/issues/2477_informative_pattern_errors.spec.ts
@@ -0,0 +1,61 @@
+import _Ajv from "../ajv2020"
+import * as assert from "assert"
+
+describe("Invalid regexp patterns should throw more informative errors (issue #2477)", () => {
+  it("throws with pattern and schema path", () => {
+    const ajv = new _Ajv()
+
+    const rootSchema = {
+      type: "string",
+      pattern: "^[0-9]{2-4}",
+    }
+
+    assert.throws(
+      () => ajv.compile(rootSchema),
+      (thrown: unknown) => {
+        assert.equal((thrown as Error).message, "Invalid regular expression: ^[0-9]{2-4} at #")
+        return true
+      }
+    )
+
+    const pathSchema = {
+      type: "object",
+      properties: {
+        foo: rootSchema,
+      },
+    }
+
+    assert.throws(
+      () => ajv.compile(pathSchema),
+      (thrown: unknown) => {
+        assert.equal(
+          (thrown as Error).message,
+          "Invalid regular expression: ^[0-9]{2-4} at #/properties/foo"
+        )
+        return true
+      }
+    )
+  })
+  it("throws with pattern and schema path with $data", () => {
+    const ajv = new _Ajv({$data: true})
+
+    const schema = {
+      properties: {
+        shouldMatch: {},
+        string: {pattern: {$data: "1/shouldMatch"}},
+      },
+    }
+    const validate = ajv.compile(schema)
+
+    assert.throws(
+      () => ajv.compile(validate({shouldMatch: "^[0-9]{2-4}", string: "123"})),
+      (thrown: unknown) => {
+        assert.equal(
+          (thrown as Error).message,
+          "Invalid regular expression: ^[0-9]{2-4} at #/properties/string"
+        )
+        return true
+      }
+    )
+  })
+})