refactor(ast): rename Formatter interface to Dialect (#4208)

Renames the Formatter interface to Dialect and refactors Format methods
to accept the dialect as a parameter instead of storing it in TrackedBuffer.

**Interface Changes:**
- Rename `format.Formatter` to `format.Dialect`
- Change Format signature from `Format(buf *TrackedBuffer)` to
  `Format(buf *TrackedBuffer, d format.Dialect)`

**TrackedBuffer Simplification:**
- Remove `formatter` field from TrackedBuffer struct
- TrackedBuffer is now a simple strings.Builder wrapper
- NewTrackedBuffer() no longer takes a dialect parameter

**Method Call Updates:**
- `buf.astFormat(x)` → `buf.astFormat(x, d)`
- `buf.join(x, sep)` → `buf.join(x, d, sep)`
- Helper methods now called directly on dialect:
  - `buf.QuoteIdent(x)` → `d.QuoteIdent(x)`
  - `buf.TypeName(ns, name)` → `d.TypeName(ns, name)`
  - `buf.Param(n)` → `d.Param(n)`
  - `buf.Cast(arg, t)` → `d.Cast(arg, t)`
  - `buf.NamedParam(name)` → `d.NamedParam(name)`

This change makes the dialect dependency explicit in Format methods
and simplifies TrackedBuffer to be purely a buffer utility.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: kyleconroy

internal/endtoend/fmt_test.go

@@ -25,7 +25,7 @@ type sqlParser interface {
 
 // sqlFormatter is an interface for formatters
 type sqlFormatter interface {
-	format.Formatter
+	format.Dialect
 }
 
 func TestFormat(t *testing.T) {

internal/engine/postgresql/reserved.go

@@ -17,7 +17,7 @@ func hasMixedCase(s string) bool {
 }
 
 // QuoteIdent returns a quoted identifier if it needs quoting.
-// This implements the format.Formatter interface.
+// This implements the format.Dialect interface.
 func (p *Parser) QuoteIdent(s string) string {
 	if p.IsReservedKeyword(s) || hasMixedCase(s) {
 		return `"` + s + `"`
@@ -26,7 +26,7 @@ func (p *Parser) QuoteIdent(s string) string {
 }
 
 // TypeName returns the SQL type name for the given namespace and name.
-// This implements the format.Formatter interface.
+// This implements the format.Dialect interface.
 func (p *Parser) TypeName(ns, name string) string {
 	if ns == "pg_catalog" {
 		switch name {

internal/sql/ast/CLAUDE.md

@@ -17,13 +17,14 @@ The `TrackedBuffer` type (`pg_query.go`) handles SQL formatting with dialect-spe
 - `QuoteIdent(name string)` - quotes identifiers (dialect-specific)
 - `TypeName(ns, name string)` - formats type names (dialect-specific)
 
-### Formatter Interface
-Dialect-specific formatting is handled via the `Formatter` interface:
+### Dialect Interface
+Dialect-specific formatting is handled via the `Dialect` interface:
 ```go
-type Formatter interface {
+type Dialect interface {
     QuoteIdent(string) string
     TypeName(ns, name string) string
     Param(int) string      // $1 for PostgreSQL, ? for MySQL
+    NamedParam(string) string // @name for PostgreSQL, :name for SQLite
     Cast(string) string
 }
 ```

internal/sql/ast/a_array_expr.go

@@ -1,5 +1,7 @@
 package ast
 
+import "github.com/sqlc-dev/sqlc/internal/sql/format"
+
 type A_ArrayExpr struct {
 	Elements *List
 	Location int
@@ -9,11 +11,11 @@ func (n *A_ArrayExpr) Pos() int {
 	return n.Location
 }
 
-func (n *A_ArrayExpr) Format(buf *TrackedBuffer) {
+func (n *A_ArrayExpr) Format(buf *TrackedBuffer, d format.Dialect) {
 	if n == nil {
 		return
 	}
 	buf.WriteString("ARRAY[")
-	buf.join(n.Elements, ", ")
+	buf.join(n.Elements, d, ", ")
 	buf.WriteString("]")
 }

internal/sql/ast/a_const.go

@@ -1,5 +1,7 @@
 package ast
 
+import "github.com/sqlc-dev/sqlc/internal/sql/format"
+
 type A_Const struct {
 	Val      Node
 	Location int
@@ -9,15 +11,15 @@ func (n *A_Const) Pos() int {
 	return n.Location
 }
 
-func (n *A_Const) Format(buf *TrackedBuffer) {
+func (n *A_Const) Format(buf *TrackedBuffer, d format.Dialect) {
 	if n == nil {
 		return
 	}
 	if _, ok := n.Val.(*String); ok {
 		buf.WriteString("'")
-		buf.astFormat(n.Val)
+		buf.astFormat(n.Val, d)
 		buf.WriteString("'")
 	} else {
-		buf.astFormat(n.Val)
+		buf.astFormat(n.Val, d)
 	}
 }

internal/sql/ast/a_expr.go

@@ -1,5 +1,7 @@
 package ast
 
+import "github.com/sqlc-dev/sqlc/internal/sql/format"
+
 type A_Expr struct {
 	Kind     A_Expr_Kind
 	Name     *List
@@ -31,75 +33,75 @@ func (n *A_Expr) isNamedParam() (string, bool) {
 	return "", false
 }
 
-func (n *A_Expr) Format(buf *TrackedBuffer) {
+func (n *A_Expr) Format(buf *TrackedBuffer, d format.Dialect) {
 	if n == nil {
 		return
 	}
 
 	// Check for named parameter first (works regardless of Kind)
 	if name, ok := n.isNamedParam(); ok {
-		buf.WriteString(buf.NamedParam(name))
+		buf.WriteString(d.NamedParam(name))
 		return
 	}
 
 	switch n.Kind {
 	case A_Expr_Kind_IN:
-		buf.astFormat(n.Lexpr)
+		buf.astFormat(n.Lexpr, d)
 		buf.WriteString(" IN (")
-		buf.astFormat(n.Rexpr)
+		buf.astFormat(n.Rexpr, d)
 		buf.WriteString(")")
 	case A_Expr_Kind_LIKE:
-		buf.astFormat(n.Lexpr)
+		buf.astFormat(n.Lexpr, d)
 		buf.WriteString(" LIKE ")
-		buf.astFormat(n.Rexpr)
+		buf.astFormat(n.Rexpr, d)
 	case A_Expr_Kind_ILIKE:
-		buf.astFormat(n.Lexpr)
+		buf.astFormat(n.Lexpr, d)
 		buf.WriteString(" ILIKE ")
-		buf.astFormat(n.Rexpr)
+		buf.astFormat(n.Rexpr, d)
 	case A_Expr_Kind_SIMILAR:
-		buf.astFormat(n.Lexpr)
+		buf.astFormat(n.Lexpr, d)
 		buf.WriteString(" SIMILAR TO ")
-		buf.astFormat(n.Rexpr)
+		buf.astFormat(n.Rexpr, d)
 	case A_Expr_Kind_BETWEEN:
-		buf.astFormat(n.Lexpr)
+		buf.astFormat(n.Lexpr, d)
 		buf.WriteString(" BETWEEN ")
 		if l, ok := n.Rexpr.(*List); ok && len(l.Items) == 2 {
-			buf.astFormat(l.Items[0])
+			buf.astFormat(l.Items[0], d)
 			buf.WriteString(" AND ")
-			buf.astFormat(l.Items[1])
+			buf.astFormat(l.Items[1], d)
 		}
 	case A_Expr_Kind_NOT_BETWEEN:
-		buf.astFormat(n.Lexpr)
+		buf.astFormat(n.Lexpr, d)
 		buf.WriteString(" NOT BETWEEN ")
 		if l, ok := n.Rexpr.(*List); ok && len(l.Items) == 2 {
-			buf.astFormat(l.Items[0])
+			buf.astFormat(l.Items[0], d)
 			buf.WriteString(" AND ")
-			buf.astFormat(l.Items[1])
+			buf.astFormat(l.Items[1], d)
 		}
 	case A_Expr_Kind_DISTINCT:
-		buf.astFormat(n.Lexpr)
+		buf.astFormat(n.Lexpr, d)
 		buf.WriteString(" IS DISTINCT FROM ")
-		buf.astFormat(n.Rexpr)
+		buf.astFormat(n.Rexpr, d)
 	case A_Expr_Kind_NOT_DISTINCT:
-		buf.astFormat(n.Lexpr)
+		buf.astFormat(n.Lexpr, d)
 		buf.WriteString(" IS NOT DISTINCT FROM ")
-		buf.astFormat(n.Rexpr)
+		buf.astFormat(n.Rexpr, d)
 	case A_Expr_Kind_NULLIF:
 		buf.WriteString("NULLIF(")
-		buf.astFormat(n.Lexpr)
+		buf.astFormat(n.Lexpr, d)
 		buf.WriteString(", ")
-		buf.astFormat(n.Rexpr)
+		buf.astFormat(n.Rexpr, d)
 		buf.WriteString(")")
 	default:
 		// Standard operator (including A_Expr_Kind_OP)
 		if set(n.Lexpr) {
-			buf.astFormat(n.Lexpr)
+			buf.astFormat(n.Lexpr, d)
 			buf.WriteString(" ")
 		}
-		buf.astFormat(n.Name)
+		buf.astFormat(n.Name, d)
 		if set(n.Rexpr) {
 			buf.WriteString(" ")
-			buf.astFormat(n.Rexpr)
+			buf.astFormat(n.Rexpr, d)
 		}
 	}
 }

internal/sql/ast/a_indices.go

@@ -1,5 +1,7 @@
 package ast
 
+import "github.com/sqlc-dev/sqlc/internal/sql/format"
+
 type A_Indices struct {
 	IsSlice bool
 	Lidx    Node
@@ -10,21 +12,21 @@ func (n *A_Indices) Pos() int {
 	return 0
 }
 
-func (n *A_Indices) Format(buf *TrackedBuffer) {
+func (n *A_Indices) Format(buf *TrackedBuffer, d format.Dialect) {
 	if n == nil {
 		return
 	}
 	buf.WriteString("[")
 	if n.IsSlice {
 		if set(n.Lidx) {
-			buf.astFormat(n.Lidx)
+			buf.astFormat(n.Lidx, d)
 		}
 		buf.WriteString(":")
 		if set(n.Uidx) {
-			buf.astFormat(n.Uidx)
+			buf.astFormat(n.Uidx, d)
 		}
 	} else {
-		buf.astFormat(n.Uidx)
+		buf.astFormat(n.Uidx, d)
 	}
 	buf.WriteString("]")
 }

internal/sql/ast/a_star.go

@@ -1,13 +1,15 @@
 package ast
 
+import "github.com/sqlc-dev/sqlc/internal/sql/format"
+
 type A_Star struct {
 }
 
 func (n *A_Star) Pos() int {
 	return 0
 }
 
-func (n *A_Star) Format(buf *TrackedBuffer) {
+func (n *A_Star) Format(buf *TrackedBuffer, d format.Dialect) {
 	if n == nil {
 		return
 	}

internal/sql/ast/alias.go

@@ -1,5 +1,7 @@
 package ast
 
+import "github.com/sqlc-dev/sqlc/internal/sql/format"
+
 type Alias struct {
 	Aliasname *string
 	Colnames  *List
@@ -9,7 +11,7 @@ func (n *Alias) Pos() int {
 	return 0
 }
 
-func (n *Alias) Format(buf *TrackedBuffer) {
+func (n *Alias) Format(buf *TrackedBuffer, d format.Dialect) {
 	if n == nil {
 		return
 	}
@@ -18,7 +20,7 @@ func (n *Alias) Format(buf *TrackedBuffer) {
 	}
 	if items(n.Colnames) {
 		buf.WriteString("(")
-		buf.astFormat((n.Colnames))
+		buf.astFormat(n.Colnames, d)
 		buf.WriteString(")")
 	}
 }

internal/sql/ast/alter_table_cmd.go

@@ -1,5 +1,7 @@
 package ast
 
+import "github.com/sqlc-dev/sqlc/internal/sql/format"
+
 const (
 	AT_AddColumn AlterTableType = iota
 	AT_AlterColumnType
@@ -40,7 +42,7 @@ func (n *AlterTableCmd) Pos() int {
 	return 0
 }
 
-func (n *AlterTableCmd) Format(buf *TrackedBuffer) {
+func (n *AlterTableCmd) Format(buf *TrackedBuffer, d format.Dialect) {
 	if n == nil {
 		return
 	}
@@ -51,5 +53,5 @@ func (n *AlterTableCmd) Format(buf *TrackedBuffer) {
 		buf.WriteString(" DROP COLUMN ")
 	}
 
-	buf.astFormat(n.Def)
+	buf.astFormat(n.Def, d)
 }