Small refactor for addreference (yoyo-project#8)

The Migrator.AddReference signature was set up to expect a db, but that
puts too much burden on the concretions to do  business logic outside of
normal dbms-specific implementation work.

This change updates the interface, migrator logic,  and mysql implementation
to clean up the implementation.

internal/dbms/base/dialect.go

@@ -19,7 +19,7 @@ func (d *Base) TypeString(dt datatype.Datatype) (string, error) {
 	return s, nil
 }
 
-func (d *Base) AddReference(table, reference string, db schema.Database, i schema.Reference) (string, error) {
+func (d *Base) AddReference(table, reference string, rt schema.Table, i schema.Reference) (string, error) {
 	panic("implement me")
 }
 

internal/dbms/base/dialect_test.go

@@ -75,7 +75,7 @@ func TestBase_Panics(t *testing.T) {
 
 	t.Run("AddReference", func(t *testing.T) {
 		panicked := didPanic(func() {
-			_, _ = b.AddReference("", "", schema.Database{}, schema.Reference{})
+			_, _ = b.AddReference("", "", schema.Table{}, schema.Reference{})
 		})
 		if !panicked {
 			t.Errorf("Expected a panic but didn't see one")

internal/dbms/mysql/migrator.go

@@ -97,27 +97,17 @@ func (m *migrator) AddIndex(tName, iName string, i schema.Index) string {
 	return fmt.Sprintf("ALTER TABLE `%s` ADD %s `%s` (%s);", tName, indexType, iName, cols.String())
 }
 
-func (m *migrator) AddReference(table, referencedTable string, db schema.Database, r schema.Reference) (string, error) {
-	sw := strings.Builder{}
-
-	if r.HasMany { // swap the tables if it's a HasMany
-		table, referencedTable = referencedTable, table
-	}
-
-	rt, ok := db.Tables[referencedTable]
-	if !ok { // This should technically be caught by validation, but still
-		return "", fmt.Errorf("referenced table `%s` does not exist in dbms definition", referencedTable)
-	}
+func (m *migrator) AddReference(table, referencedTable string, refTable schema.Table, ref schema.Reference) (string, error) {
 	var (
 		fcols       []string
 		fknames     []string
 		fkname      string
-		refColNames = r.ColumnNames
+		hasPK       bool
+		refColNames = ref.ColumnNames
+		sw          = strings.Builder{}
 	)
 
-	var hasPK bool
-
-	for cname, col := range rt.Columns {
+	for cname, col := range refTable.Columns {
 		if !col.PrimaryKey {
 			continue
 		}
@@ -127,8 +117,8 @@ func (m *migrator) AddReference(table, referencedTable string, db schema.Databas
 		switch {
 		case len(refColNames) > 0:
 			fkname, refColNames = refColNames[0], refColNames[1:len(refColNames)]
-		case len(r.ColumnName) > 0:
-			fkname = r.ColumnName
+		case len(ref.ColumnName) > 0:
+			fkname = ref.ColumnName
 		default:
 			fkname = fmt.Sprintf("fk_%s_%s", referencedTable, cname)
 		}
@@ -140,7 +130,7 @@ func (m *migrator) AddReference(table, referencedTable string, db schema.Databas
 		sw.WriteRune('\n')
 	}
 
-	if len(r.ColumnNames) > 0 && len(r.ColumnNames) != len(fcols) {
+	if len(ref.ColumnNames) > 0 && len(ref.ColumnNames) != len(fcols) {
 		return "", fmt.Errorf("cannot add reference from `%s` to `%s`: length of column_names does not match length of primary keys", table, referencedTable)
 	}
 
@@ -152,12 +142,12 @@ func (m *migrator) AddReference(table, referencedTable string, db schema.Databas
 		table, referencedTable, strings.Join(fknames, ", "), referencedTable, strings.Join(fcols, ", "),
 	))
 
-	if r.OnDelete != "" {
-		sw.WriteString(fmt.Sprintf(" ON DELETE %s", r.OnDelete))
+	if ref.OnDelete != "" {
+		sw.WriteString(fmt.Sprintf(" ON DELETE %s", ref.OnDelete))
 	}
 
-	if r.OnUpdate != "" {
-		sw.WriteString(fmt.Sprintf(" ON UPDATE %s", r.OnUpdate))
+	if ref.OnUpdate != "" {
+		sw.WriteString(fmt.Sprintf(" ON UPDATE %s", ref.OnUpdate))
 	}
 
 	return sw.String(), nil

internal/dbms/mysql/reverser_test.go

@@ -1010,7 +1010,7 @@ func Test_reverser_GetReference(t *testing.T) {
 				t.Errorf("ListTables() error = %v, wantErr %v", err, tt.wantErr)
 				return
 			}
-			if  tt.wantErr == "" && !reflect.DeepEqual(got, tt.want) {
+			if tt.wantErr == "" && !reflect.DeepEqual(got, tt.want) {
 				t.Errorf("ListTables() got = %v, want %v", got, tt.want)
 			}
 		})

internal/migration/dialect.go

@@ -20,7 +20,7 @@ type Dialect interface {
 	AddIndex(table, index string, i schema.Index) string
 
 	// AddReference returns a string query which adds the specified index to a table
-	AddReference(table, referencedTable string, db schema.Database, i schema.Reference) (string, error)
+	AddReference(table, referencedTable string, dt schema.Table, i schema.Reference) (string, error)
 }
 
 func LoadDialect(name string) (d Dialect, err error) {

internal/migration/generator.go

@@ -147,6 +147,11 @@ func NewRefAdder(
 ) RefGenerator {
 	return func(localTable string, refs map[string]schema.Reference, sw io.StringWriter) error {
 		for foreignTable, ref := range refs {
+			if ref.HasMany { // swap the tables if it's a HasMany
+				localTable, foreignTable = foreignTable, localTable
+			}
+			ft, ok := db.Tables[foreignTable]
+
 			if options&AddMissing > 0 {
 				exists, err := hasReference(localTable, foreignTable)
 				if err != nil {
@@ -157,7 +162,11 @@ func NewRefAdder(
 					continue
 				}
 			}
-			s, err := d.AddReference(localTable, foreignTable, db, ref)
+
+			if !ok { // This should technically be caught by validation, but still
+				return fmt.Errorf("referenced table `%s` does not exist in dbms definition", foreignTable)
+			}
+			s, err := d.AddReference(localTable, foreignTable, ft, ref)
 			if err != nil {
 				return fmt.Errorf("unable to generate migration: %w", err)
 			}

internal/migration/generator_dialect_test.go

@@ -16,7 +16,7 @@ func (d *mockDialect) DataSourceName(host, username, schema, password, port stri
 	return ""
 }
 
-func (d *mockDialect) AddReference(table, referencedTable string, db schema.Database, i schema.Reference) (string, error) {
+func (d *mockDialect) AddReference(table, referencedTable string, rt schema.Table, i schema.Reference) (string, error) {
 	return "", nil
 }