[FE-3134] fix(studio): handle ALTER TABLE IF EXISTS in RLS detection (#45493)

The SQL Editor was warning about missing RLS even when the same query
enabled it, if the user wrote `ALTER TABLE IF EXISTS ...`. The parser
regex didn't recognise `IF EXISTS` and was capturing `IF` as the table
name, so the RLS event never matched the `CREATE TABLE`.

**Changed:**
- `ALTER TABLE` regex in `sql-event-parser.ts` now accepts the optional
`IF EXISTS` and `ONLY` modifiers, matching Postgres's `ALTER TABLE [ IF
EXISTS ] [ ONLY ] name` grammar.

**Added:**
- Unit tests for `IF EXISTS`, `ONLY`, and both combined.
- Regression test in `SQLEditor.utils.test.ts` using the customer's
exact SQL.

## To test

1. Open the SQL Editor and paste:

```sql
CREATE TABLE IF NOT EXISTS public."Conversations" (id int8 primary key);
ALTER TABLE IF EXISTS public."Conversations" ENABLE ROW LEVEL SECURITY;
```

2. Hit Run – the "table will not have RLS" warning should **not**
appear.
3. Sanity check: a `CREATE TABLE` without any matching `ENABLE ROW LEVEL
SECURITY` still triggers the warning.

Addresses
[FE-3134](https://linear.app/supabase/issue/FE-3134/sql-editor-warns-about-missing-rls-policy-incorrectly).

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Tests**
* Added comprehensive test coverage for Row Level Security detection
across different SQL syntax patterns and clause combinations

* **Bug Fixes**
* Enhanced Row Level Security detection capabilities in the SQL editor
by extending support for additional ALTER TABLE statement syntax
variations, improving the accuracy and completeness of security
configuration recognition

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: Alaister Young <10985857+alaister@users.noreply.github.com>

apps/studio/components/interfaces/SQLEditor/SQLEditor.utils.test.ts

@@ -414,6 +414,15 @@ describe('SQLEditor.utils:getCreateTablesMissingRLS', () => {
     expect(getCreateTablesMissingRLS(sql)).toEqual([])
   })
 
+  it('does not flag when ALTER TABLE IF EXISTS enables RLS', () => {
+    const sql = stripIndent`
+      CREATE TABLE IF NOT EXISTS public."Conversations" (id int8 primary key);
+      ALTER TABLE IF EXISTS public."Conversations" ENABLE ROW LEVEL SECURITY;
+      GRANT ALL ON TABLE public."Conversations" TO postgres, anon, authenticated, service_role;
+    `
+    expect(getCreateTablesMissingRLS(sql)).toEqual([])
+  })
+
   it('flags CREATE TEMP TABLE', () => {
     const result = getCreateTablesMissingRLS('create temp table foo (id int8 primary key);')
     expect(result).toHaveLength(1)

apps/studio/lib/sql-event-parser.test.ts

@@ -288,6 +288,42 @@ describe('SQL Event Parser', () => {
       const results = sqlEventParser.getTableEvents('ALTER TABLE users DISABLE ROW LEVEL SECURITY')
       expect(results).toHaveLength(0)
     })
+
+    it('detects ALTER TABLE IF EXISTS ENABLE ROW LEVEL SECURITY', () => {
+      const results = sqlEventParser.getTableEvents(
+        'ALTER TABLE IF EXISTS public."Conversations" ENABLE ROW LEVEL SECURITY'
+      )
+      expect(results).toHaveLength(1)
+      expect(results[0]).toEqual({
+        type: TABLE_EVENT_ACTIONS.TableRLSEnabled,
+        schema: 'public',
+        tableName: 'Conversations',
+      })
+    })
+
+    it('detects ALTER TABLE ONLY ENABLE ROW LEVEL SECURITY', () => {
+      const results = sqlEventParser.getTableEvents(
+        'ALTER TABLE ONLY public.users ENABLE ROW LEVEL SECURITY'
+      )
+      expect(results).toHaveLength(1)
+      expect(results[0]).toEqual({
+        type: TABLE_EVENT_ACTIONS.TableRLSEnabled,
+        schema: 'public',
+        tableName: 'users',
+      })
+    })
+
+    it('detects ALTER TABLE IF EXISTS ONLY ENABLE ROW LEVEL SECURITY', () => {
+      const results = sqlEventParser.getTableEvents(
+        'ALTER TABLE IF EXISTS ONLY public.users ENABLE ROW LEVEL SECURITY'
+      )
+      expect(results).toHaveLength(1)
+      expect(results[0]).toEqual({
+        type: TABLE_EVENT_ACTIONS.TableRLSEnabled,
+        schema: 'public',
+        tableName: 'users',
+      })
+    })
   })
 
   describe('ReDoS protection', () => {

apps/studio/lib/sql-event-parser.ts

@@ -39,8 +39,8 @@ export class SQLEventParser {
     {
       type: TABLE_EVENT_ACTIONS.TableRLSEnabled,
       patterns: [
-        /ALTER\s+TABLE\s+(?<schema>(?:"[^"]+"|[\w]+)\.)?(?<table>(?:"(?:[^"]|"")+"|`(?:[^`]|``)+`|[\w]+)).*?ENABLE\s+ROW\s+LEVEL\s+SECURITY/i,
-        /ALTER\s+TABLE\s+(?<schema>(?:"[^"]+"|[\w]+)\.)?(?<table>(?:"(?:[^"]|"")+"|`(?:[^`]|``)+`|[\w]+)).*?ENABLE\s+RLS/i,
+        /ALTER\s+TABLE\s+(?:IF\s+EXISTS\s+)?(?:ONLY\s+)?(?<schema>(?:"[^"]+"|[\w]+)\.)?(?<table>(?:"(?:[^"]|"")+"|`(?:[^`]|``)+`|[\w]+)).*?ENABLE\s+ROW\s+LEVEL\s+SECURITY/i,
+        /ALTER\s+TABLE\s+(?:IF\s+EXISTS\s+)?(?:ONLY\s+)?(?<schema>(?:"[^"]+"|[\w]+)\.)?(?<table>(?:"(?:[^"]|"")+"|`(?:[^`]|``)+`|[\w]+)).*?ENABLE\s+RLS/i,
       ],
     },
   ]