feat(reader): 🎉 Add support for multi-file DBML loading

* Implement directory reading for DBML files.
* Merge schemas and tables from multiple files.
* Add tests for multi-file loading and merging behavior.
* Enhance file discovery and sorting logic.

.github/workflows/integration-tests.yml

@@ -46,6 +46,11 @@ jobs:
     - name: Download dependencies
       run: go mod download
 
+    - name: Install PostgreSQL client
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y postgresql-client
+
     - name: Initialize test database
       env:
         PGPASSWORD: relspec_test_password

pkg/readers/bun/reader.go

@@ -632,6 +632,9 @@ func (r *Reader) parseColumn(fieldName string, fieldType ast.Expr, tag string, s
 		column.Name = parts[0]
 	}
 
+	// Track if we found explicit nullability markers
+	hasExplicitNullableMarker := false
+
 	// Parse tag attributes
 	for _, part := range parts[1:] {
 		kv := strings.SplitN(part, ":", 2)
@@ -649,6 +652,10 @@ func (r *Reader) parseColumn(fieldName string, fieldType ast.Expr, tag string, s
 			column.IsPrimaryKey = true
 		case "notnull":
 			column.NotNull = true
+			hasExplicitNullableMarker = true
+		case "nullzero":
+			column.NotNull = false
+			hasExplicitNullableMarker = true
 		case "autoincrement":
 			column.AutoIncrement = true
 		case "default":
@@ -664,17 +671,15 @@ func (r *Reader) parseColumn(fieldName string, fieldType ast.Expr, tag string, s
 
 	// Determine if nullable based on Go type and bun tags
 	// In Bun:
-	// - nullzero tag means the field is nullable (can be NULL in DB)
+	// - explicit "notnull" tag means NOT NULL
-	// - absence of nullzero means the field is NOT NULL
+	// - explicit "nullzero" tag means nullable
-	// - primitive types (int64, bool, string) are NOT NULL by default
+	// - absence of explicit markers: infer from Go type
-	column.NotNull = true
+	if !hasExplicitNullableMarker {
-	// Primary keys are always NOT NULL
+		// Infer from Go type if no explicit marker found
-
-	if strings.Contains(bunTag, "nullzero") {
-		column.NotNull = false
-	} else {
 		column.NotNull = !r.isNullableGoType(fieldType)
 	}
+
+	// Primary keys are always NOT NULL
 	if column.IsPrimaryKey {
 		column.NotNull = true
 	}

pkg/readers/dbml/reader.go

@@ -4,7 +4,9 @@ import (
 	"bufio"
 	"fmt"
 	"os"
+	"path/filepath"
 	"regexp"
+	"sort"
 	"strings"
 
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
@@ -24,11 +26,23 @@ func NewReader(options *readers.ReaderOptions) *Reader {
 }
 
 // ReadDatabase reads and parses DBML input, returning a Database model
+// If FilePath points to a directory, all .dbml files are loaded and merged
 func (r *Reader) ReadDatabase() (*models.Database, error) {
 	if r.options.FilePath == "" {
 		return nil, fmt.Errorf("file path is required for DBML reader")
 	}
 
+	// Check if path is a directory
+	info, err := os.Stat(r.options.FilePath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to stat path: %w", err)
+	}
+
+	if info.IsDir() {
+		return r.readDirectoryDBML(r.options.FilePath)
+	}
+
+	// Single file - existing logic
 	content, err := os.ReadFile(r.options.FilePath)
 	if err != nil {
 		return nil, fmt.Errorf("failed to read file: %w", err)
@@ -67,6 +81,53 @@ func (r *Reader) ReadTable() (*models.Table, error) {
 	return schema.Tables[0], nil
 }
 
+// readDirectoryDBML processes all .dbml files in directory
+// Returns merged Database model
+func (r *Reader) readDirectoryDBML(dirPath string) (*models.Database, error) {
+	// Discover and sort DBML files
+	files, err := r.discoverDBMLFiles(dirPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to discover DBML files: %w", err)
+	}
+
+	// If no files found, return empty database
+	if len(files) == 0 {
+		db := models.InitDatabase("database")
+		if r.options.Metadata != nil {
+			if name, ok := r.options.Metadata["name"].(string); ok {
+				db.Name = name
+			}
+		}
+		return db, nil
+	}
+
+	// Initialize database (will be merged with files)
+	var db *models.Database
+
+	// Process each file in sorted order
+	for _, filePath := range files {
+		content, err := os.ReadFile(filePath)
+		if err != nil {
+			return nil, fmt.Errorf("failed to read file %s: %w", filePath, err)
+		}
+
+		fileDB, err := r.parseDBML(string(content))
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse file %s: %w", filePath, err)
+		}
+
+		// First file initializes the database
+		if db == nil {
+			db = fileDB
+		} else {
+			// Subsequent files are merged
+			mergeDatabase(db, fileDB)
+		}
+	}
+
+	return db, nil
+}
+
 // stripQuotes removes surrounding quotes from an identifier
 func stripQuotes(s string) string {
 	s = strings.TrimSpace(s)
@@ -76,6 +137,235 @@ func stripQuotes(s string) string {
 	return s
 }
 
+// parseFilePrefix extracts numeric prefix from filename
+// Examples: "1_schema.dbml" -> (1, true), "tables.dbml" -> (0, false)
+func parseFilePrefix(filename string) (int, bool) {
+	base := filepath.Base(filename)
+	re := regexp.MustCompile(`^(\d+)[_-]`)
+	matches := re.FindStringSubmatch(base)
+	if len(matches) > 1 {
+		var prefix int
+		_, err := fmt.Sscanf(matches[1], "%d", &prefix)
+		if err == nil {
+			return prefix, true
+		}
+	}
+	return 0, false
+}
+
+// hasCommentedRefs scans file content for commented-out Ref statements
+// Returns true if file contains lines like: // Ref: table.col > other.col
+func hasCommentedRefs(filePath string) (bool, error) {
+	content, err := os.ReadFile(filePath)
+	if err != nil {
+		return false, err
+	}
+
+	scanner := bufio.NewScanner(strings.NewReader(string(content)))
+	commentedRefRegex := regexp.MustCompile(`^\s*//.*Ref:\s+`)
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		if commentedRefRegex.MatchString(line) {
+			return true, nil
+		}
+	}
+
+	return false, nil
+}
+
+// discoverDBMLFiles finds all .dbml files in directory and returns them sorted
+func (r *Reader) discoverDBMLFiles(dirPath string) ([]string, error) {
+	pattern := filepath.Join(dirPath, "*.dbml")
+	files, err := filepath.Glob(pattern)
+	if err != nil {
+		return nil, fmt.Errorf("failed to glob .dbml files: %w", err)
+	}
+
+	return sortDBMLFiles(files), nil
+}
+
+// sortDBMLFiles sorts files by:
+// 1. Files without commented refs (by numeric prefix, then alphabetically)
+// 2. Files with commented refs (by numeric prefix, then alphabetically)
+func sortDBMLFiles(files []string) []string {
+	// Create a slice to hold file info for sorting
+	type fileInfo struct {
+		path         string
+		hasCommented bool
+		prefix       int
+		hasPrefix    bool
+		basename     string
+	}
+
+	fileInfos := make([]fileInfo, 0, len(files))
+
+	for _, file := range files {
+		hasCommented, err := hasCommentedRefs(file)
+		if err != nil {
+			// If we can't read the file, treat it as not having commented refs
+			hasCommented = false
+		}
+
+		prefix, hasPrefix := parseFilePrefix(file)
+		basename := filepath.Base(file)
+
+		fileInfos = append(fileInfos, fileInfo{
+			path:         file,
+			hasCommented: hasCommented,
+			prefix:       prefix,
+			hasPrefix:    hasPrefix,
+			basename:     basename,
+		})
+	}
+
+	// Sort by: hasCommented (false first), hasPrefix (true first), prefix, basename
+	sort.Slice(fileInfos, func(i, j int) bool {
+		// First, sort by commented refs (files without commented refs come first)
+		if fileInfos[i].hasCommented != fileInfos[j].hasCommented {
+			return !fileInfos[i].hasCommented
+		}
+
+		// Then by presence of prefix (files with prefix come first)
+		if fileInfos[i].hasPrefix != fileInfos[j].hasPrefix {
+			return fileInfos[i].hasPrefix
+		}
+
+		// If both have prefix, sort by prefix value
+		if fileInfos[i].hasPrefix && fileInfos[j].hasPrefix {
+			if fileInfos[i].prefix != fileInfos[j].prefix {
+				return fileInfos[i].prefix < fileInfos[j].prefix
+			}
+		}
+
+		// Finally, sort alphabetically by basename
+		return fileInfos[i].basename < fileInfos[j].basename
+	})
+
+	// Extract sorted paths
+	sortedFiles := make([]string, len(fileInfos))
+	for i, info := range fileInfos {
+		sortedFiles[i] = info.path
+	}
+
+	return sortedFiles
+}
+
+// mergeTable combines two table definitions
+// Merges: Columns (map), Constraints (map), Indexes (map), Relationships (map)
+// Uses first non-empty Description
+func mergeTable(baseTable, fileTable *models.Table) {
+	// Merge columns (map naturally merges - later keys overwrite)
+	for key, col := range fileTable.Columns {
+		baseTable.Columns[key] = col
+	}
+
+	// Merge constraints
+	for key, constraint := range fileTable.Constraints {
+		baseTable.Constraints[key] = constraint
+	}
+
+	// Merge indexes
+	for key, index := range fileTable.Indexes {
+		baseTable.Indexes[key] = index
+	}
+
+	// Merge relationships
+	for key, rel := range fileTable.Relationships {
+		baseTable.Relationships[key] = rel
+	}
+
+	// Use first non-empty description
+	if baseTable.Description == "" && fileTable.Description != "" {
+		baseTable.Description = fileTable.Description
+	}
+
+	// Merge metadata maps
+	if baseTable.Metadata == nil {
+		baseTable.Metadata = make(map[string]any)
+	}
+	for key, val := range fileTable.Metadata {
+		baseTable.Metadata[key] = val
+	}
+}
+
+// mergeSchema finds or creates schema and merges tables
+func mergeSchema(baseDB *models.Database, fileSchema *models.Schema) {
+	// Find existing schema by name (normalize names by stripping quotes)
+	var existingSchema *models.Schema
+	fileSchemaName := stripQuotes(fileSchema.Name)
+	for _, schema := range baseDB.Schemas {
+		if stripQuotes(schema.Name) == fileSchemaName {
+			existingSchema = schema
+			break
+		}
+	}
+
+	// If schema doesn't exist, add it and return
+	if existingSchema == nil {
+		baseDB.Schemas = append(baseDB.Schemas, fileSchema)
+		return
+	}
+
+	// Merge tables from fileSchema into existingSchema
+	for _, fileTable := range fileSchema.Tables {
+		// Find existing table by name (normalize names by stripping quotes)
+		var existingTable *models.Table
+		fileTableName := stripQuotes(fileTable.Name)
+		for _, table := range existingSchema.Tables {
+			if stripQuotes(table.Name) == fileTableName {
+				existingTable = table
+				break
+			}
+		}
+
+		// If table doesn't exist, add it
+		if existingTable == nil {
+			existingSchema.Tables = append(existingSchema.Tables, fileTable)
+		} else {
+			// Merge table properties - tables are identical, skip
+			mergeTable(existingTable, fileTable)
+		}
+	}
+
+	// Merge other schema properties
+	existingSchema.Views = append(existingSchema.Views, fileSchema.Views...)
+	existingSchema.Sequences = append(existingSchema.Sequences, fileSchema.Sequences...)
+	existingSchema.Scripts = append(existingSchema.Scripts, fileSchema.Scripts...)
+
+	// Merge permissions
+	if existingSchema.Permissions == nil {
+		existingSchema.Permissions = make(map[string]string)
+	}
+	for key, val := range fileSchema.Permissions {
+		existingSchema.Permissions[key] = val
+	}
+
+	// Merge metadata
+	if existingSchema.Metadata == nil {
+		existingSchema.Metadata = make(map[string]any)
+	}
+	for key, val := range fileSchema.Metadata {
+		existingSchema.Metadata[key] = val
+	}
+}
+
+// mergeDatabase merges schemas from fileDB into baseDB
+func mergeDatabase(baseDB, fileDB *models.Database) {
+	// Merge each schema from fileDB
+	for _, fileSchema := range fileDB.Schemas {
+		mergeSchema(baseDB, fileSchema)
+	}
+
+	// Merge domains
+	baseDB.Domains = append(baseDB.Domains, fileDB.Domains...)
+
+	// Use first non-empty description
+	if baseDB.Description == "" && fileDB.Description != "" {
+		baseDB.Description = fileDB.Description
+	}
+}
+
 // parseDBML parses DBML content and returns a Database model
 func (r *Reader) parseDBML(content string) (*models.Database, error) {
 	db := models.InitDatabase("database")
@@ -332,27 +622,31 @@ func (r *Reader) parseIndex(line, tableName, schemaName string) *models.Index {
 	// Format: (columns) [attributes] OR columnname [attributes]
 	var columns []string
 
-	if strings.Contains(line, "(") && strings.Contains(line, ")") {
+	// Find the attributes section to avoid parsing parentheses in notes/attributes
+	attrStart := strings.Index(line, "[")
+	columnPart := line
+	if attrStart > 0 {
+		columnPart = line[:attrStart]
+	}
+
+	if strings.Contains(columnPart, "(") && strings.Contains(columnPart, ")") {
 		// Multi-column format: (col1, col2) [attributes]
-		colStart := strings.Index(line, "(")
+		colStart := strings.Index(columnPart, "(")
-		colEnd := strings.Index(line, ")")
+		colEnd := strings.Index(columnPart, ")")
 		if colStart >= colEnd {
 			return nil
 		}
 
-		columnsStr := line[colStart+1 : colEnd]
+		columnsStr := columnPart[colStart+1 : colEnd]
 		for _, col := range strings.Split(columnsStr, ",") {
 			columns = append(columns, stripQuotes(strings.TrimSpace(col)))
 		}
-	} else if strings.Contains(line, "[") {
+	} else if attrStart > 0 {
 		// Single column format: columnname [attributes]
 		// Extract column name before the bracket
-		idx := strings.Index(line, "[")
+		colName := strings.TrimSpace(columnPart)
-		if idx > 0 {
+		if colName != "" {
-			colName := strings.TrimSpace(line[:idx])
+			columns = []string{stripQuotes(colName)}
-			if colName != "" {
-				columns = []string{stripQuotes(colName)}
-			}
 		}
 	}
 

pkg/readers/dbml/reader_test.go

@@ -1,6 +1,7 @@
 package dbml
 
 import (
+	"os"
 	"path/filepath"
 	"testing"
 
@@ -517,3 +518,286 @@ func TestGetForeignKeys(t *testing.T) {
 		t.Error("Expected foreign key constraint type")
 	}
 }
+
+// Tests for multi-file directory loading
+
+func TestReadDirectory_MultipleFiles(t *testing.T) {
+	opts := &readers.ReaderOptions{
+		FilePath: filepath.Join("..", "..", "..", "tests", "assets", "dbml", "multifile"),
+	}
+
+	reader := NewReader(opts)
+	db, err := reader.ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() error = %v", err)
+	}
+
+	if db == nil {
+		t.Fatal("ReadDatabase() returned nil database")
+	}
+
+	// Should have public schema
+	if len(db.Schemas) == 0 {
+		t.Fatal("Expected at least one schema")
+	}
+
+	var publicSchema *models.Schema
+	for _, schema := range db.Schemas {
+		if schema.Name == "public" {
+			publicSchema = schema
+			break
+		}
+	}
+
+	if publicSchema == nil {
+		t.Fatal("Public schema not found")
+	}
+
+	// Should have 3 tables: users, posts, comments
+	if len(publicSchema.Tables) != 3 {
+		t.Fatalf("Expected 3 tables, got %d", len(publicSchema.Tables))
+	}
+
+	// Find tables
+	var usersTable, postsTable, commentsTable *models.Table
+	for _, table := range publicSchema.Tables {
+		switch table.Name {
+		case "users":
+			usersTable = table
+		case "posts":
+			postsTable = table
+		case "comments":
+			commentsTable = table
+		}
+	}
+
+	if usersTable == nil {
+		t.Fatal("Users table not found")
+	}
+	if postsTable == nil {
+		t.Fatal("Posts table not found")
+	}
+	if commentsTable == nil {
+		t.Fatal("Comments table not found")
+	}
+
+	// Verify users table has merged columns from 1_users.dbml and 3_add_columns.dbml
+	expectedUserColumns := []string{"id", "email", "name", "created_at"}
+	if len(usersTable.Columns) != len(expectedUserColumns) {
+		t.Errorf("Expected %d columns in users table, got %d", len(expectedUserColumns), len(usersTable.Columns))
+	}
+
+	for _, colName := range expectedUserColumns {
+		if _, exists := usersTable.Columns[colName]; !exists {
+			t.Errorf("Expected column '%s' in users table", colName)
+		}
+	}
+
+	// Verify posts table columns
+	expectedPostColumns := []string{"id", "user_id", "title", "content", "created_at"}
+	for _, colName := range expectedPostColumns {
+		if _, exists := postsTable.Columns[colName]; !exists {
+			t.Errorf("Expected column '%s' in posts table", colName)
+		}
+	}
+}
+
+func TestReadDirectory_TableMerging(t *testing.T) {
+	opts := &readers.ReaderOptions{
+		FilePath: filepath.Join("..", "..", "..", "tests", "assets", "dbml", "multifile"),
+	}
+
+	reader := NewReader(opts)
+	db, err := reader.ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() error = %v", err)
+	}
+
+	// Find users table
+	var usersTable *models.Table
+	for _, schema := range db.Schemas {
+		for _, table := range schema.Tables {
+			if table.Name == "users" && schema.Name == "public" {
+				usersTable = table
+				break
+			}
+		}
+	}
+
+	if usersTable == nil {
+		t.Fatal("Users table not found")
+	}
+
+	// Verify columns from file 1 (id, email)
+	if _, exists := usersTable.Columns["id"]; !exists {
+		t.Error("Column 'id' from 1_users.dbml not found")
+	}
+	if _, exists := usersTable.Columns["email"]; !exists {
+		t.Error("Column 'email' from 1_users.dbml not found")
+	}
+
+	// Verify columns from file 3 (name, created_at)
+	if _, exists := usersTable.Columns["name"]; !exists {
+		t.Error("Column 'name' from 3_add_columns.dbml not found")
+	}
+	if _, exists := usersTable.Columns["created_at"]; !exists {
+		t.Error("Column 'created_at' from 3_add_columns.dbml not found")
+	}
+
+	// Verify column properties from file 1
+	emailCol := usersTable.Columns["email"]
+	if !emailCol.NotNull {
+		t.Error("Email column should be not null (from 1_users.dbml)")
+	}
+	if emailCol.Type != "varchar(255)" {
+		t.Errorf("Expected email type 'varchar(255)', got '%s'", emailCol.Type)
+	}
+}
+
+func TestReadDirectory_CommentedRefsLast(t *testing.T) {
+	// This test verifies that files with commented refs are processed last
+	// by checking that the file discovery returns them in the correct order
+	dirPath := filepath.Join("..", "..", "..", "tests", "assets", "dbml", "multifile")
+
+	opts := &readers.ReaderOptions{
+		FilePath: dirPath,
+	}
+
+	reader := NewReader(opts)
+	files, err := reader.discoverDBMLFiles(dirPath)
+	if err != nil {
+		t.Fatalf("discoverDBMLFiles() error = %v", err)
+	}
+
+	if len(files) < 2 {
+		t.Skip("Not enough files to test ordering")
+	}
+
+	// Check that 9_refs.dbml (which has commented refs) comes last
+	lastFile := filepath.Base(files[len(files)-1])
+	if lastFile != "9_refs.dbml" {
+		t.Errorf("Expected last file to be '9_refs.dbml' (has commented refs), got '%s'", lastFile)
+	}
+
+	// Check that numbered files without commented refs come first
+	firstFile := filepath.Base(files[0])
+	if firstFile != "1_users.dbml" {
+		t.Errorf("Expected first file to be '1_users.dbml', got '%s'", firstFile)
+	}
+}
+
+func TestReadDirectory_EmptyDirectory(t *testing.T) {
+	// Create a temporary empty directory
+	tmpDir := filepath.Join("..", "..", "..", "tests", "assets", "dbml", "empty_test_dir")
+	err := os.MkdirAll(tmpDir, 0755)
+	if err != nil {
+		t.Fatalf("Failed to create temp directory: %v", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	opts := &readers.ReaderOptions{
+		FilePath: tmpDir,
+	}
+
+	reader := NewReader(opts)
+	db, err := reader.ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() should not error on empty directory, got: %v", err)
+	}
+
+	if db == nil {
+		t.Fatal("ReadDatabase() returned nil database")
+	}
+
+	// Empty directory should return empty database
+	if len(db.Schemas) != 0 {
+		t.Errorf("Expected 0 schemas for empty directory, got %d", len(db.Schemas))
+	}
+}
+
+func TestReadDatabase_BackwardCompat(t *testing.T) {
+	// Test that single file loading still works
+	opts := &readers.ReaderOptions{
+		FilePath: filepath.Join("..", "..", "..", "tests", "assets", "dbml", "simple.dbml"),
+	}
+
+	reader := NewReader(opts)
+	db, err := reader.ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() error = %v", err)
+	}
+
+	if db == nil {
+		t.Fatal("ReadDatabase() returned nil database")
+	}
+
+	if len(db.Schemas) == 0 {
+		t.Fatal("Expected at least one schema")
+	}
+
+	schema := db.Schemas[0]
+	if len(schema.Tables) != 1 {
+		t.Fatalf("Expected 1 table, got %d", len(schema.Tables))
+	}
+
+	table := schema.Tables[0]
+	if table.Name != "users" {
+		t.Errorf("Expected table name 'users', got '%s'", table.Name)
+	}
+}
+
+func TestParseFilePrefix(t *testing.T) {
+	tests := []struct {
+		filename   string
+		wantPrefix int
+		wantHas    bool
+	}{
+		{"1_schema.dbml", 1, true},
+		{"2_tables.dbml", 2, true},
+		{"10_relationships.dbml", 10, true},
+		{"99_data.dbml", 99, true},
+		{"schema.dbml", 0, false},
+		{"tables_no_prefix.dbml", 0, false},
+		{"/path/to/1_file.dbml", 1, true},
+		{"/path/to/file.dbml", 0, false},
+		{"1-file.dbml", 1, true},
+		{"2-another.dbml", 2, true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.filename, func(t *testing.T) {
+			gotPrefix, gotHas := parseFilePrefix(tt.filename)
+			if gotPrefix != tt.wantPrefix {
+				t.Errorf("parseFilePrefix(%s) prefix = %d, want %d", tt.filename, gotPrefix, tt.wantPrefix)
+			}
+			if gotHas != tt.wantHas {
+				t.Errorf("parseFilePrefix(%s) hasPrefix = %v, want %v", tt.filename, gotHas, tt.wantHas)
+			}
+		})
+	}
+}
+
+func TestHasCommentedRefs(t *testing.T) {
+	// Test with the actual multifile test fixtures
+	tests := []struct {
+		filename string
+		wantHas  bool
+	}{
+		{filepath.Join("..", "..", "..", "tests", "assets", "dbml", "multifile", "1_users.dbml"), false},
+		{filepath.Join("..", "..", "..", "tests", "assets", "dbml", "multifile", "2_posts.dbml"), false},
+		{filepath.Join("..", "..", "..", "tests", "assets", "dbml", "multifile", "3_add_columns.dbml"), false},
+		{filepath.Join("..", "..", "..", "tests", "assets", "dbml", "multifile", "9_refs.dbml"), true},
+	}
+
+	for _, tt := range tests {
+		t.Run(filepath.Base(tt.filename), func(t *testing.T) {
+			gotHas, err := hasCommentedRefs(tt.filename)
+			if err != nil {
+				t.Fatalf("hasCommentedRefs() error = %v", err)
+			}
+			if gotHas != tt.wantHas {
+				t.Errorf("hasCommentedRefs(%s) = %v, want %v", filepath.Base(tt.filename), gotHas, tt.wantHas)
+			}
+		})
+	}
+}

pkg/writers/bun/type_mapper.go

@@ -192,8 +192,11 @@ func (tm *TypeMapper) BuildBunTag(column *models.Column, table *models.Table) st
 	}
 
 	// Nullable (Bun uses nullzero for nullable fields)
+	// and notnull tag for explicitly non-nullable fields
 	if !column.NotNull && !column.IsPrimaryKey {
 		parts = append(parts, "nullzero")
+	} else if column.NotNull && !column.IsPrimaryKey {
+		parts = append(parts, "notnull")
 	}
 
 	// Check for indexes (unique indexes should be added to tag)

pkg/writers/dbml/writer.go

@@ -126,7 +126,15 @@ func (w *Writer) tableToDBML(t *models.Table) string {
 			attrs = append(attrs, "increment")
 		}
 		if column.Default != nil {
-			attrs = append(attrs, fmt.Sprintf("default: `%v`", column.Default))
+			// Check if default value contains backticks (DBML expressions like `now()`)
+			defaultStr := fmt.Sprintf("%v", column.Default)
+			if strings.HasPrefix(defaultStr, "`") && strings.HasSuffix(defaultStr, "`") {
+				// Already an expression with backticks, use as-is
+				attrs = append(attrs, fmt.Sprintf("default: %s", defaultStr))
+			} else {
+				// Regular value, wrap in single quotes
+				attrs = append(attrs, fmt.Sprintf("default: '%v'", column.Default))
+			}
 		}
 
 		if len(attrs) > 0 {

tests/assets/dbml/multifile/1_users.dbml

@@ -0,0 +1,5 @@
+// First file - users table basic structure
+Table public.users {
+  id bigint [pk, increment]
+  email varchar(255) [unique, not null]
+}

tests/assets/dbml/multifile/2_posts.dbml

@@ -0,0 +1,8 @@
+// Second file - posts table
+Table public.posts {
+  id bigint [pk, increment]
+  user_id bigint [not null]
+  title varchar(200) [not null]
+  content text
+  created_at timestamp [not null]
+}

tests/assets/dbml/multifile/3_add_columns.dbml

@@ -0,0 +1,5 @@
+// Third file - adds more columns to users table (tests merging)
+Table public.users {
+  name varchar(100)
+  created_at timestamp [not null]
+}

tests/assets/dbml/multifile/9_refs.dbml

@@ -0,0 +1,10 @@
+// File with commented-out refs - should load last
+// Contains relationships that depend on earlier tables
+
+// Ref: public.posts.user_id > public.users.id [ondelete: CASCADE]
+
+Table public.comments {
+  id bigint [pk, increment]
+  post_id bigint [not null]
+  content text [not null]
+}