From 5b2ecea52bf01a9af1b8248f3ece243c75ac9594 Mon Sep 17 00:00:00 2001
From: =?utf8?q?J=C3=A9r=C3=B4me=20Benoit?= <jerome.benoit@piment-noir.org>
Date: Sun, 22 Feb 2026 23:51:47 +0100
Subject: [PATCH] test: add custom toMatchObject matcher for @std/expect
 compatibility

Implement custom Vitest matcher that replicates @std/expect's toMatchObject
semantics for arrays. The matcher handles sparse array subset matching where
only defined indices are compared, matching the behavior of @std/expect's
spread-based algorithm in _equal.ts.

This fixes 8 failing tests in queue test files that use toMatchObject with
sparse arrays created via new Array(capacity).
---
 tests/vitest.setup.mjs | 149 +++++++++++++++++++++++++++++++++++++++++
 vitest.config.ts       |   1 +
 2 files changed, 150 insertions(+)
 create mode 100644 tests/vitest.setup.mjs

diff --git a/tests/vitest.setup.mjs b/tests/vitest.setup.mjs
new file mode 100644
index 000000000..29d8468b3
--- /dev/null
+++ b/tests/vitest.setup.mjs
@@ -0,0 +1,149 @@
+import { expect } from 'vitest'
+
+/**
+ * Format a value for display in error messages
+ * @param value
+ * @param indent
+ */
+function formatValue (value, indent = 0) {
+  const spaces = '  '.repeat(indent)
+  if (value === null) return 'null'
+  if (value === undefined) return 'undefined'
+  if (typeof value === 'string') return JSON.stringify(value)
+  if (typeof value === 'number' || typeof value === 'boolean') { return String(value) }
+  if (Array.isArray(value)) {
+    if (value.length === 0) return '[]'
+    const items = value
+      .map((item, index) => {
+        if (!(index in value)) return `${spaces}  <empty>`
+        return `${spaces}  ${formatValue(item, indent + 1)}`
+      })
+      .join(',\n')
+    return `[\n${items}\n${spaces}]`
+  }
+  if (typeof value === 'object') {
+    if (
+      typeof value.asymmetricMatch === 'function' &&
+      value.toString !== Object.prototype.toString
+    ) {
+      return value.toString()
+    }
+    const keys = Object.keys(value)
+    if (keys.length === 0) return '{}'
+    const items = keys
+      .map(key => `${spaces}  ${key}: ${formatValue(value[key], indent + 1)}`)
+      .join(',\n')
+    return `{\n${items}\n${spaces}}`
+  }
+  return String(value)
+}
+
+/**
+ * Custom matcher that replicates @std/expect's toMatchObject semantics for arrays.
+ *
+ * Key difference from Vitest's built-in toMatchObject:
+ * - For arrays: only checks that each element in `expected` matches the corresponding
+ *   element in `received` at the same index. Extra elements in `received` are ignored.
+ * - For objects: checks that all keys in `expected` exist in `received` with matching values.
+ *   Extra keys in `received` are ignored.
+ *
+ * This matches the behavior of @std/expect from Deno which uses subsetEquality.
+ * @param received
+ * @param expected
+ * @param asymmetricMatchers
+ */
+function subsetMatch (received, expected, asymmetricMatchers) {
+  // Handle asymmetric matchers (like expect.any(Number))
+  if (
+    expected != null &&
+    typeof expected === 'object' &&
+    typeof expected.asymmetricMatch === 'function'
+  ) {
+    return expected.asymmetricMatch(received)
+  }
+
+  // Handle null/undefined
+  if (expected === null || expected === undefined) {
+    return received === expected
+  }
+
+  // Handle primitives
+  if (typeof expected !== 'object') {
+    return Object.is(received, expected)
+  }
+
+  // Handle Date objects
+  if (expected instanceof Date) {
+    return received instanceof Date && received.getTime() === expected.getTime()
+  }
+
+  // Handle RegExp objects
+  if (expected instanceof RegExp) {
+    return (
+      received instanceof RegExp &&
+      received.source === expected.source &&
+      received.flags === expected.flags
+    )
+  }
+
+  // Handle arrays - this is the key difference from Vitest's toMatchObject
+  // We only check elements up to expected.length
+  if (Array.isArray(expected)) {
+    if (!Array.isArray(received)) {
+      return false
+    }
+    // Check each element in expected matches the corresponding element in received
+    for (let i = 0; i < expected.length; i++) {
+      // Skip sparse array slots (undefined created by `new Array(n)`)
+      if (!(i in expected)) {
+        continue
+      }
+      if (!(i in received)) {
+        return false
+      }
+      if (!subsetMatch(received[i], expected[i], asymmetricMatchers)) {
+        return false
+      }
+    }
+    return true
+  }
+
+  // Handle plain objects - subset matching
+  if (typeof received !== 'object' || received === null) {
+    return false
+  }
+
+  // Check all keys in expected exist in received with matching values
+  for (const key of Object.keys(expected)) {
+    if (!(key in received)) {
+      return false
+    }
+    if (!subsetMatch(received[key], expected[key], asymmetricMatchers)) {
+      return false
+    }
+  }
+
+  return true
+}
+
+expect.extend({
+  /**
+   * Custom toMatchObject that replicates @std/expect semantics.
+   * This overrides Vitest's built-in toMatchObject for array subset matching.
+   * @param received
+   * @param expected
+   */
+  toMatchObject (received, expected) {
+    const pass = subsetMatch(received, expected)
+
+    return {
+      message: () => {
+        if (pass) {
+          return `expected ${formatValue(received)} not to match object ${formatValue(expected)}`
+        }
+        return `expected ${formatValue(received)} to match object ${formatValue(expected)}`
+      },
+      pass,
+    }
+  },
+})
diff --git a/vitest.config.ts b/vitest.config.ts
index 21c98edaa..e80f9e30d 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -18,6 +18,7 @@ export default defineConfig({
     sequence: {
       hooks: 'list',
     },
+    setupFiles: ['./tests/vitest.setup.mjs'],
     testTimeout: 30000,
   },
 })
-- 
2.43.0