require-field-index: add support for functions in indexes (#774)

I wanted to enable the `require-field-index` in my project when I got an
error message:
```
Error: value is not a string array {"type":"function","name":"endDate","params":[{"type":"keyValue","key":"sort","value":"Desc","location":{"startLine":125,"startColumn":19,"startOffset":4111,"endLine":125,"endColumn":22,"endOffset":4114}}],"location":{"startLine":125,"startColumn":11,"startOffset":4103,"endLine":125,"endColumn":17,"endOffset":4109}}
    at assertValueIsStringArray (file:///Users/<...>/node_modules/prisma-lint/dist/common/prisma.js:83:11)
```

The line that failed the parsing here is an index with a `sort` option
set ([relevant Prisma
docs](https://www.prisma.io/docs/orm/prisma-schema/data-model/indexes#configuring-the-index-sort-order-with-sort)):
```prisma
@@index([endDate(sort: Desc)])
```

I gave a stab at fixing this myself, let me know what you think!

Author: dios-david

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- Add support for index functions (e.g. `@@index(createdAt(sort: Desc))`) in `require-field-index` rule.
+
 ## 0.10.2 (2025-05-24)
 
 - [#683](https://github.com/loop-payments/prisma-lint/issues/683) Stop requiring defaults for `@ignored` relation fields.

src/common/prisma.ts

@@ -4,6 +4,7 @@ import type {
   BlockAttribute,
   Enum as PrismaEnum,
   Field,
+  Func,
   KeyValue,
   Model,
   Schema,
@@ -108,9 +109,15 @@ export function isKeyValue(value: Value | KeyValue): value is KeyValue {
   return false;
 }
 
-export function assertValueIsStringArray(value: Value): Array<string> {
+export function isFunc(value: Value): value is Func {
+  return (
+    typeof value === 'object' && 'type' in value && value.type === 'function'
+  );
+}
+
+export function assertValueIsArray(value: Value): Array<Value> {
   if (Array.isArray(value)) {
-    return value as Array<string>;
+    return value as Array<Value>;
   }
 
   if (typeof value === 'object') {
@@ -119,7 +126,7 @@ export function assertValueIsStringArray(value: Value): Array<string> {
     }
   }
 
-  throw new Error(`value is not a string array ${JSON.stringify(value)}`);
+  throw new Error(`value is not an array ${JSON.stringify(value)}`);
 }
 
 export function looksLikeAssociationFieldType(fieldType: any) {

src/rules/require-field-index.test.ts

@@ -151,6 +151,32 @@ describe('require-field-index', () => {
       });
     });
 
+    describe('with function in @@index', () => {
+      it('returns violation', async () => {
+        const violations = await run(`
+      model Users {
+        tenantQid String
+        createdAt DateTime
+        @@index(tenantQid(sort: Desc))
+      }
+    `);
+        expect(violations.length).toEqual(0);
+      });
+    });
+
+    describe('with function in compound @@index', () => {
+      it('returns violation', async () => {
+        const violations = await run(`
+      model Users {
+        tenantQid String
+        createdAt DateTime
+        @@index([tenantQid(sort: Desc), createdAt])
+      }
+    `);
+        expect(violations.length).toEqual(0);
+      });
+    });
+
     describe('with no index', () => {
       it('returns violation', async () => {
         const violations = await run(`

src/rules/require-field-index.ts

@@ -9,7 +9,8 @@ import { z } from 'zod';
 
 import { getRuleIgnoreParams as listRuleIgnoreParams } from '#src/common/ignore.js';
 import {
-  assertValueIsStringArray,
+  assertValueIsArray,
+  isFunc,
   isKeyValue,
   isValue,
   listAttributes,
@@ -240,13 +241,22 @@ function extractPrimaryFieldNameFromRelationListAttribute(
     return value;
   }
 
+  // @@index(value(sort: Desc))
+  if (isFunc(value)) {
+    return value.name;
+  }
+
   // @@index([value]) or @@unique([value])
-  const [firstFieldValue] = assertValueIsStringArray(value);
+  const [firstFieldValue] = assertValueIsArray(value);
   if (typeof firstFieldValue === 'string') {
-    // it should always be a string
     return firstFieldValue;
   }
 
+  // @@index([value(sort: Desc)])
+  if (isFunc(firstFieldValue)) {
+    return firstFieldValue.name;
+  }
+
   throw new Error('Failed to parse attribute, first value is not a string');
 }
 
@@ -267,5 +277,5 @@ function extractRelationFieldNames(field: Field): Array<string> {
   }
 
   const fieldsArgValue = (fieldsArg.value as KeyValue).value;
-  return assertValueIsStringArray(fieldsArgValue);
+  return assertValueIsArray(fieldsArgValue) as string[];
 }