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/sqlite/generated_test.go

@@ -0,0 +1,64 @@
+package sqlite
+
+import (
+	"database/sql"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/readers"
+)
+
+func TestParseGeneratedExpression(t *testing.T) {
+	createSQL := `CREATE TABLE people (
+		id INTEGER PRIMARY KEY,
+		"first" TEXT,
+		last TEXT,
+		full_name TEXT GENERATED ALWAYS AS (coalesce("first", '') || ' ' || last) STORED,
+		initials TEXT AS (substr("first", 1, 1) || substr(last, 1, 1)),
+		plain TEXT NOT NULL
+	)`
+
+	tests := []struct {
+		column string
+		want   string
+	}{
+		{"full_name", `coalesce("first", '') || ' ' || last`},
+		{"initials", `substr("first", 1, 1) || substr(last, 1, 1)`},
+		{"plain", ""},
+		{"missing", ""},
+	}
+	for _, tt := range tests {
+		t.Run(tt.column, func(t *testing.T) {
+			assert.Equal(t, tt.want, parseGeneratedExpression(createSQL, tt.column))
+		})
+	}
+}
+
+func TestReader_GeneratedColumns(t *testing.T) {
+	dbPath := filepath.Join(t.TempDir(), "gen.db")
+	db, err := sql.Open("sqlite", dbPath)
+	require.NoError(t, err)
+	_, err = db.Exec(`CREATE TABLE people (
+		id INTEGER PRIMARY KEY,
+		first TEXT,
+		last TEXT,
+		full_name TEXT GENERATED ALWAYS AS (first || ' ' || last) STORED,
+		initials TEXT AS (substr(first, 1, 1) || substr(last, 1, 1))
+	)`)
+	require.NoError(t, err)
+	require.NoError(t, db.Close())
+
+	got, err := NewReader(&readers.ReaderOptions{FilePath: dbPath}).ReadDatabase()
+	require.NoError(t, err)
+
+	cols := got.Schemas[0].Tables[0].Columns
+	require.Contains(t, cols, "full_name", "generated columns must be read")
+	assert.True(t, cols["full_name"].Generated)
+	assert.Equal(t, "first || ' ' || last", cols["full_name"].GenerationExpression)
+	assert.True(t, cols["initials"].Generated)
+	assert.Equal(t, "substr(first, 1, 1) || substr(last, 1, 1)", cols["initials"].GenerationExpression)
+	assert.False(t, cols["first"].Generated)
+}