From 7771d1afec6a6a1fa024dd0726de69b16f2e7603 Mon Sep 17 00:00:00 2001
From: Konstantin Grachev <me@grachevko.ru>
Date: Tue, 23 Sep 2025 18:44:07 +0300
Subject: [PATCH] fix: properly handle nested parentheses in check constraint
 normalization

- Add balanced parentheses validation before removing outer parentheses
- Prevent incorrect normalization of complex expressions with nested parentheses
- Improve robustness of CHECK constraint parsing logic
---
 internal/ir/normalize.go                      | 12 ++++++---
 testdata/diff/create_table/add_check/diff.sql |  2 ++
 testdata/diff/create_table/add_check/new.sql  |  3 +++
 testdata/diff/create_table/add_check/old.sql  |  3 +++
 .../diff/create_table/add_check/plan.json     | 26 +++++++++++++++++++
 testdata/diff/create_table/add_check/plan.sql |  4 +++
 testdata/diff/create_table/add_check/plan.txt | 16 ++++++++++++
 7 files changed, 63 insertions(+), 3 deletions(-)
 create mode 100644 testdata/diff/create_table/add_check/diff.sql
 create mode 100644 testdata/diff/create_table/add_check/new.sql
 create mode 100644 testdata/diff/create_table/add_check/old.sql
 create mode 100644 testdata/diff/create_table/add_check/plan.json
 create mode 100644 testdata/diff/create_table/add_check/plan.sql
 create mode 100644 testdata/diff/create_table/add_check/plan.txt

diff --git a/internal/ir/normalize.go b/internal/ir/normalize.go
index c2cb6a4d..8a07e5ac 100644
--- a/internal/ir/normalize.go
+++ b/internal/ir/normalize.go
@@ -849,9 +849,15 @@ func normalizeCheckClause(checkClause string) string {
 		clause = after
 	}
 
-	// Remove outer parentheses if present (may be multiple layers)
-	for strings.HasPrefix(clause, "(") && strings.HasSuffix(clause, ")") {
-		clause = strings.TrimSpace(clause[1 : len(clause)-1])
+	// Remove ONLY outer parentheses if they are balanced and not part of complex expression
+	clause = strings.TrimSpace(clause)
+	for len(clause) > 0 && clause[0] == '(' && clause[len(clause)-1] == ')' {
+		// Check if parentheses are balanced
+		if isBalancedParentheses(clause[1 : len(clause)-1]) {
+			clause = strings.TrimSpace(clause[1 : len(clause)-1])
+		} else {
+			break
+		}
 	}
 
 	// First apply legacy conversions to handle PostgreSQL-specific patterns
diff --git a/testdata/diff/create_table/add_check/diff.sql b/testdata/diff/create_table/add_check/diff.sql
new file mode 100644
index 00000000..2b331ac2
--- /dev/null
+++ b/testdata/diff/create_table/add_check/diff.sql
@@ -0,0 +1,2 @@
+ALTER TABLE code
+    ADD CONSTRAINT code_check CHECK (code > 0 AND code < 255);
diff --git a/testdata/diff/create_table/add_check/new.sql b/testdata/diff/create_table/add_check/new.sql
new file mode 100644
index 00000000..305df777
--- /dev/null
+++ b/testdata/diff/create_table/add_check/new.sql
@@ -0,0 +1,3 @@
+CREATE TABLE public.code (
+    code integer PRIMARY KEY CONSTRAINT code_check CHECK (code > 0 AND code < 255)
+);
diff --git a/testdata/diff/create_table/add_check/old.sql b/testdata/diff/create_table/add_check/old.sql
new file mode 100644
index 00000000..83f90eaf
--- /dev/null
+++ b/testdata/diff/create_table/add_check/old.sql
@@ -0,0 +1,3 @@
+CREATE TABLE IF NOT EXISTS code (
+    code integer PRIMARY KEY
+);
diff --git a/testdata/diff/create_table/add_check/plan.json b/testdata/diff/create_table/add_check/plan.json
new file mode 100644
index 00000000..c61b665c
--- /dev/null
+++ b/testdata/diff/create_table/add_check/plan.json
@@ -0,0 +1,26 @@
+{
+  "version": "1.0.0",
+  "pgschema_version": "1.1.0",
+  "created_at": "2025-09-23T18:49:35+03:00",
+  "source_fingerprint": {
+    "hash": "a9d472cd406e27485b570b72906ad224b8282469bd50699bddd6da04acdabaef"
+  },
+  "groups": [
+    {
+      "steps": [
+        {
+          "sql": "ALTER TABLE code\nADD CONSTRAINT code_check CHECK (code > 0 AND code < 255) NOT VALID;",
+          "type": "table.constraint",
+          "operation": "create",
+          "path": "public.code.code_check"
+        },
+        {
+          "sql": "ALTER TABLE code VALIDATE CONSTRAINT code_check;",
+          "type": "table.constraint",
+          "operation": "create",
+          "path": "public.code.code_check"
+        }
+      ]
+    }
+  ]
+}
diff --git a/testdata/diff/create_table/add_check/plan.sql b/testdata/diff/create_table/add_check/plan.sql
new file mode 100644
index 00000000..6254472d
--- /dev/null
+++ b/testdata/diff/create_table/add_check/plan.sql
@@ -0,0 +1,4 @@
+ALTER TABLE code
+ADD CONSTRAINT code_check CHECK (code > 0 AND code < 255) NOT VALID;
+
+ALTER TABLE code VALIDATE CONSTRAINT code_check;
diff --git a/testdata/diff/create_table/add_check/plan.txt b/testdata/diff/create_table/add_check/plan.txt
new file mode 100644
index 00000000..49234554
--- /dev/null
+++ b/testdata/diff/create_table/add_check/plan.txt
@@ -0,0 +1,16 @@
+Plan: 1 to modify.
+
+Summary by type:
+  tables: 1 to modify
+
+Tables:
+  ~ code
+    + code_check (constraint)
+
+DDL to be executed:
+--------------------------------------------------
+
+ALTER TABLE code
+ADD CONSTRAINT code_check CHECK (code > 0 AND code < 255) NOT VALID;
+
+ALTER TABLE code VALIDATE CONSTRAINT code_check;