fix: match array fields in where filters

src/app.test.ts

@@ -169,6 +169,20 @@ await test('createApp', async (t) => {
     assert.deepEqual(data, { error: 'Body must be a JSON object' })
   })
 
+  await t.test('GET /businesses?categories.id=... filters on array fields', async () => {
+    const business1 = { id: '1', categories: [{ id: 1 }, { id: 2 }] }
+    const business2 = { id: '2', categories: [{ id: 3 }] }
+    db.data = { businesses: [business1, business2] }
+
+    const matching = await fetch(`http://localhost:${port}/businesses?categories.id=2`)
+    assert.equal(matching.status, 200)
+    assert.deepEqual(await matching.json(), [business1])
+
+    const empty = await fetch(`http://localhost:${port}/businesses?categories.id=10`)
+    assert.equal(empty.status, 200)
+    assert.deepEqual(await empty.json(), [])
+  })
+
   await t.test('PUT /posts/1 with null body returns 400', async () => {
     const response = await fetch(`http://localhost:${port}/posts/1`, {
       method: 'PUT',

src/matches-where.test.ts

@@ -6,7 +6,17 @@ import type { JsonObject } from 'type-fest'
 import { matchesWhere } from './matches-where.ts'
 
 await test('matchesWhere', async (t) => {
-  const obj: JsonObject = { a: 10, b: 20, c: 'x', nested: { a: 10, b: 20 } }
+  const obj: JsonObject = {
+    a: 10,
+    b: 20,
+    c: 'x',
+    nested: { a: 10, b: 20 },
+    items: [
+      { id: 1, name: 'foo' },
+      { id: 2, name: 'bar' },
+    ],
+    tags: ['red', 'blue'],
+  }
   const cases: [JsonObject, boolean][] = [
     [{ a: { eq: 10 } }, true],
     [{ a: { eq: 11 } }, false],
@@ -53,6 +63,21 @@ await test('matchesWhere', async (t) => {
     [{ c: { endsWith: 'z' } }, false],
     [{ a: { endsWith: '1' } }, false],
     [{ c: { endsWith: 1 } }, false],
+    // Array fields match when at least one item matches
+    [{ items: { id: { eq: 1 } } }, true],
+    [{ items: { id: { eq: 2 } } }, true],
+    [{ items: { id: { eq: 10 } } }, false],
+    [{ items: { id: { gt: 1 } } }, true],
+    [{ items: { id: { gt: 2 } } }, false],
+    [{ items: { name: { contains: 'BA' } } }, true],
+    [{ items: { name: { contains: 'baz' } } }, false],
+    // All conditions must be met by the same item
+    [{ items: { id: { eq: 1 }, name: { eq: 'foo' } } }, true],
+    [{ items: { id: { eq: 1 }, name: { eq: 'bar' } } }, false],
+    // Arrays of primitives have no properties to match
+    [{ tags: { id: { eq: 1 } } }, false],
+    [{ or: [{ items: { id: { eq: 10 } } }, { a: { eq: 10 } }] }, true],
+    [{ or: [{ items: { id: { eq: 10 } } }, { a: { eq: 11 } }] }, false],
   ]
 
   for (const [query, expected] of cases) {

src/matches-where.ts

@@ -72,6 +72,13 @@ export function matchesWhere(obj: JsonObject, where: JsonObject): boolean {
         continue
       }
 
+      // An array matches if at least one of its items matches
+      if (Array.isArray(field)) {
+        const matched = field.some((item) => isJSONObject(item) && matchesWhere(item, value))
+        if (!matched) return false
+        continue
+      }
+
       if (isJSONObject(field)) {
         if (!matchesWhere(field, value)) return false
       }