From 389535a9fd6ed7e0d5d46fafa789121986d5288c Mon Sep 17 00:00:00 2001
From: Naoki Takahashi <lazinelia@gmail.com>
Date: Fri, 6 Feb 2026 22:40:19 +0900
Subject: [PATCH] fix(db): strip MySQL display widths from INTEGER types during
 export
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MySQL's information_schema returns display widths (e.g., 10 for INT,
11 for INT(11)) as numeric_precision. These display widths were being
incorrectly preserved as Strata's semantic precision, causing false
type-change diffs like "INTEGER → INTEGER(10)" during round-trip
operations (export → generate).

Fixes #26

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../src/adapters/type_mapping/mysql_mapper.rs | 83 ++++++++++++++++++-
 1 file changed, 80 insertions(+), 3 deletions(-)

diff --git a/src/db/src/adapters/type_mapping/mysql_mapper.rs b/src/db/src/adapters/type_mapping/mysql_mapper.rs
index 692a73d..f089629 100644
--- a/src/db/src/adapters/type_mapping/mysql_mapper.rs
+++ b/src/db/src/adapters/type_mapping/mysql_mapper.rs
@@ -12,7 +12,9 @@ impl TypeMapper for MySqlTypeMapper {
     fn parse_sql_type(&self, sql_type: &str, metadata: &TypeMetadata) -> Option<ColumnType> {
         match sql_type {
             "int" | "integer" => Some(ColumnType::INTEGER {
-                precision: metadata.numeric_precision,
+                // MySQL の display width（INT(10) 等）はストリップする。
+                // Strata の precision は意味的な精度であり、表示幅ではない。
+                precision: None,
             }),
             "smallint" => Some(ColumnType::INTEGER { precision: Some(2) }),
             "bigint" => Some(ColumnType::INTEGER { precision: Some(8) }),
@@ -31,7 +33,8 @@ impl TypeMapper for MySqlTypeMapper {
                     Some(ColumnType::BOOLEAN)
                 } else {
                     Some(ColumnType::INTEGER {
-                        precision: metadata.numeric_precision,
+                        // MySQL の display width をストリップする
+                        precision: None,
                     })
                 }
             }
@@ -288,7 +291,8 @@ mod tests {
             ..Default::default()
         };
         let result = mapper.parse_sql_type("tinyint", &metadata).unwrap();
-        assert!(matches!(result, ColumnType::INTEGER { precision: Some(1) }));
+        // display width はストリップされるので precision: None になる
+        assert!(matches!(result, ColumnType::INTEGER { precision: None }));
     }
 
     #[test]
@@ -543,6 +547,79 @@ mod tests {
         assert!(matches!(result, ColumnType::TEXT));
     }
 
+    // =========================================================================
+    // Issue #26: MySQL INTEGER display width regression tests
+    // =========================================================================
+
+    #[test]
+    fn test_mysql_parse_int_strips_display_width() {
+        // MySQL の information_schema は INT に numeric_precision=10 を返す。
+        // Strata ではこの display width をストリップして precision: None にすべき。
+        let mapper = MySqlTypeMapper;
+        let metadata = TypeMetadata {
+            numeric_precision: Some(10),
+            ..Default::default()
+        };
+        let result = mapper.parse_sql_type("int", &metadata).unwrap();
+        assert!(matches!(result, ColumnType::INTEGER { precision: None }));
+    }
+
+    #[test]
+    fn test_mysql_parse_integer_strips_display_width() {
+        let mapper = MySqlTypeMapper;
+        let metadata = TypeMetadata {
+            numeric_precision: Some(10),
+            ..Default::default()
+        };
+        let result = mapper.parse_sql_type("integer", &metadata).unwrap();
+        assert!(matches!(result, ColumnType::INTEGER { precision: None }));
+    }
+
+    #[test]
+    fn test_mysql_parse_int_11_strips_display_width() {
+        // INT(11) (signed INT のデフォルト display width) もストリップされる
+        let mapper = MySqlTypeMapper;
+        let metadata = TypeMetadata {
+            numeric_precision: Some(11),
+            ..Default::default()
+        };
+        let result = mapper.parse_sql_type("int", &metadata).unwrap();
+        assert!(matches!(result, ColumnType::INTEGER { precision: None }));
+    }
+
+    #[test]
+    fn test_mysql_parse_tinyint_non_boolean_strips_display_width() {
+        // TINYINT で precision != 3 の場合も display width をストリップする
+        let mapper = MySqlTypeMapper;
+        let metadata = TypeMetadata {
+            numeric_precision: Some(4),
+            ..Default::default()
+        };
+        let result = mapper.parse_sql_type("tinyint", &metadata).unwrap();
+        assert!(matches!(result, ColumnType::INTEGER { precision: None }));
+    }
+
+    #[test]
+    fn test_mysql_int_roundtrip_no_spurious_precision() {
+        // INT → export → re-import で precision が付与されないことを確認
+        let service = TypeMappingService::new(Dialect::MySQL);
+        let mapper = MySqlTypeMapper;
+
+        // MySQL introspection が返す metadata をシミュレート
+        let metadata = TypeMetadata {
+            numeric_precision: Some(10),
+            ..Default::default()
+        };
+
+        // parse: "int" + precision=10 → INTEGER { precision: None }
+        let parsed = mapper.parse_sql_type("int", &metadata).unwrap();
+        assert!(matches!(parsed, ColumnType::INTEGER { precision: None }));
+
+        // format: INTEGER { precision: None } → "INT"
+        let sql = service.to_sql_type(&parsed);
+        assert_eq!(sql, "INT");
+    }
+
     // =========================================================================
     // Issue #25: MySQL dialect-specific type regression tests
     // =========================================================================