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/writers/drizzle/README.md

@@ -113,6 +113,7 @@ export const postsRelations = relations(posts, ({ one }) => ({
 
 ## Notes
 
+- Generated columns: `.generatedAlwaysAs(sql`expr`)`; identity columns: `.generatedAlwaysAsIdentity()` / `.generatedByDefaultAsIdentity()`
 - Table names and column names are preserved as-is
 - Relationships are generated as separate relation definitions
 - Constraint actions (CASCADE, etc.) are included in references

pkg/writers/drizzle/generated_columns_test.go

@@ -0,0 +1,71 @@
+package drizzle
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+	"git.warky.dev/wdevs/relspecgo/pkg/readers"
+	drizzlereader "git.warky.dev/wdevs/relspecgo/pkg/readers/drizzle"
+	"git.warky.dev/wdevs/relspecgo/pkg/writers"
+)
+
+func TestGeneratedAndIdentityColumnsRoundTrip(t *testing.T) {
+	table := models.InitTable("people", "public")
+
+	id := models.InitColumn("id", "people", "public")
+	id.Type = "bigint"
+	id.IsPrimaryKey = true
+	id.AutoIncrement = true
+	id.Identity = true
+	id.IdentityGeneration = "ALWAYS"
+	table.Columns["id"] = id
+
+	seq := models.InitColumn("seq", "people", "public")
+	seq.Type = "integer"
+	seq.AutoIncrement = true
+	seq.Identity = true
+	seq.IdentityGeneration = "BY DEFAULT"
+	table.Columns["seq"] = seq
+
+	first := models.InitColumn("first", "people", "public")
+	first.Type = "text"
+	table.Columns["first"] = first
+
+	full := models.InitColumn("full_name", "people", "public")
+	full.Type = "text"
+	full.Generated = true
+	full.GenerationExpression = "first || ' ' || upper(first)"
+	table.Columns["full_name"] = full
+
+	schema := models.InitSchema("public")
+	schema.Tables = append(schema.Tables, table)
+	db := models.InitDatabase("testdb")
+	db.Schemas = append(db.Schemas, schema)
+
+	out := filepath.Join(t.TempDir(), "schema.ts")
+	require.NoError(t, NewWriter(&writers.WriterOptions{OutputPath: out}).WriteDatabase(db))
+
+	content, err := os.ReadFile(out)
+	require.NoError(t, err)
+	assert.Contains(t, string(content), "generatedAlwaysAs(sql`first || ' ' || upper(first)`)")
+	assert.Contains(t, string(content), "generatedAlwaysAsIdentity()")
+	assert.Contains(t, string(content), "generatedByDefaultAsIdentity()")
+
+	got, err := drizzlereader.NewReader(&readers.ReaderOptions{FilePath: out}).ReadDatabase()
+	require.NoError(t, err)
+	cols := got.Schemas[0].Tables[0].Columns
+
+	assert.True(t, cols["id"].Identity)
+	assert.Equal(t, "ALWAYS", cols["id"].IdentityGeneration)
+	assert.True(t, cols["seq"].Identity)
+	assert.Equal(t, "BY DEFAULT", cols["seq"].IdentityGeneration)
+	assert.True(t, cols["full_name"].Generated)
+	assert.Equal(t, "first || ' ' || upper(first)", cols["full_name"].GenerationExpression)
+	assert.False(t, cols["first"].Generated)
+	assert.False(t, cols["first"].Identity)
+}

pkg/writers/drizzle/type_mapper.go

@@ -140,7 +140,13 @@ func (tm *TypeMapper) buildColumnModifiers(col *models.Column, table *models.Tab
 	}
 
 	// Default value
-	if col.AutoIncrement {
+	if col.Generated && col.GenerationExpression != "" {
+		// GENERATED ALWAYS AS (expr) STORED
+		expr := strings.ReplaceAll(col.GenerationExpression, "`", "\\`")
+		modifiers = append(modifiers, fmt.Sprintf("generatedAlwaysAs(sql`%s`)", expr))
+	} else if col.Identity && strings.EqualFold(col.IdentityGeneration, "BY DEFAULT") {
+		modifiers = append(modifiers, "generatedByDefaultAsIdentity()")
+	} else if col.AutoIncrement || col.Identity {
 		// For auto-increment, use generatedAlwaysAsIdentity()
 		modifiers = append(modifiers, "generatedAlwaysAsIdentity()")
 	} else if col.Default != nil {