feat: generated and identity columns for mssql, sqlite, drizzle, typeorm, bun and gorm readers

- mssql: write computed columns (AS (expr) PERSISTED) and identity; read computed definition and identity
- sqlite: write GENERATED ALWAYS AS (expr) STORED; read generated columns via table_xinfo and parse the expression
- drizzle: generatedAlwaysAs / generated(Always|ByDefault)AsIdentity, read and write
- typeorm: asExpression/generatedType and identity decorators, read and write; decorator scan is now quote-aware
- bun, gorm readers: read generated and identity markers
- readmes updated

pkg/readers/mssql/README.md

@@ -25,6 +25,11 @@ sqlserver://user:pass@192.168.1.100:1433/production
 sqlserver://localhost/testdb?encrypt=disable
 ```
 
+## Computed and Identity Columns
+
+- `sys.computed_columns` -> `Generated` + `GenerationExpression` (outer parentheses removed; persisted or not)
+- Identity columns -> `Identity` + `IdentityGeneration = ALWAYS`
+
 ## Supported Constraints
 
 - Primary Keys

pkg/readers/mssql/queries.go

@@ -104,8 +104,12 @@ func (r *Reader) queryColumns(schemaName string) (map[string]map[string]*models.
 			c.numeric_precision,
 			c.numeric_scale,
 			ISNULL(ep.value, '') as description,
-			COLUMNPROPERTY(OBJECT_ID(QUOTENAME(c.table_schema) + '.' + QUOTENAME(c.table_name)), c.column_name, 'IsIdentity') as is_identity
+			COLUMNPROPERTY(OBJECT_ID(QUOTENAME(c.table_schema) + '.' + QUOTENAME(c.table_name)), c.column_name, 'IsIdentity') as is_identity,
+			cc.definition as computed_definition
 		FROM information_schema.columns c
+		LEFT JOIN sys.computed_columns cc
+			ON cc.object_id = OBJECT_ID(QUOTENAME(c.table_schema) + '.' + QUOTENAME(c.table_name))
+			AND cc.name = c.column_name
 		LEFT JOIN sys.extended_properties ep
 			ON ep.major_id = OBJECT_ID(QUOTENAME(c.table_schema) + '.' + QUOTENAME(c.table_name))
 			AND ep.minor_id = COLUMNPROPERTY(OBJECT_ID(QUOTENAME(c.table_schema) + '.' + QUOTENAME(c.table_name)), c.column_name, 'ColumnId')
@@ -127,8 +131,9 @@ func (r *Reader) queryColumns(schemaName string) (map[string]map[string]*models.
 		var schema, tableName, columnName, isNullable, dataType, description string
 		var ordinalPosition int
 		var columnDefault, charMaxLength, numPrecision, numScale, isIdentity *int
+		var computedDefinition *string
 
-		if err := rows.Scan(&schema, &tableName, &columnName, &ordinalPosition, &columnDefault, &isNullable, &dataType, &charMaxLength, &numPrecision, &numScale, &description, &isIdentity); err != nil {
+		if err := rows.Scan(&schema, &tableName, &columnName, &ordinalPosition, &columnDefault, &isNullable, &dataType, &charMaxLength, &numPrecision, &numScale, &description, &isIdentity, &computedDefinition); err != nil {
 			return nil, err
 		}
 
@@ -144,6 +149,14 @@ func (r *Reader) queryColumns(schemaName string) (map[string]map[string]*models.
 		// Check if this is an identity column (auto-increment)
 		if isIdentity != nil && *isIdentity == 1 {
 			column.AutoIncrement = true
+			column.Identity = true
+			column.IdentityGeneration = "ALWAYS"
+		}
+
+		// Computed columns report their expression wrapped in an extra pair of parentheses
+		if computedDefinition != nil && strings.TrimSpace(*computedDefinition) != "" {
+			column.Generated = true
+			column.GenerationExpression = trimOuterParens(*computedDefinition)
 		}
 
 		if charMaxLength != nil && *charMaxLength > 0 {
@@ -414,3 +427,25 @@ func (r *Reader) queryIndexes(schemaName string) (map[string][]*models.Index, er
 
 	return indexes, rows.Err()
 }
+
+// trimOuterParens removes one pair of parentheses wrapping the whole expression, as
+// SQL Server stores computed column definitions.
+func trimOuterParens(expr string) string {
+	expr = strings.TrimSpace(expr)
+	if len(expr) < 2 || expr[0] != '(' || expr[len(expr)-1] != ')' {
+		return expr
+	}
+	depth := 0
+	for i := 0; i < len(expr); i++ {
+		switch expr[i] {
+		case '(':
+			depth++
+		case ')':
+			depth--
+			if depth == 0 && i != len(expr)-1 {
+				return expr
+			}
+		}
+	}
+	return strings.TrimSpace(expr[1 : len(expr)-1])
+}

pkg/readers/mssql/reader_test.go

@@ -85,3 +85,18 @@ func TestConvertMSSQLToCanonical(t *testing.T) {
 		})
 	}
 }
+
+func TestTrimOuterParens(t *testing.T) {
+	tests := map[string]string{
+		"(([a])+([b]))":   "([a])+([b])",
+		"([a]+[b])":       "[a]+[b]",
+		"([a])+([b])":     "([a])+([b])",
+		"[a]+[b]":         "[a]+[b]",
+		"  (upper([a])) ": "upper([a])",
+	}
+	for in, want := range tests {
+		if got := trimOuterParens(in); got != want {
+			t.Errorf("trimOuterParens(%q) = %q, want %q", in, got, want)
+		}
+	}
+}