Pool EmitContext (#1287)

Author: jakebailey

internal/compiler/emitter.go

@@ -133,7 +133,9 @@ func (e *emitter) emitJSFile(sourceFile *ast.SourceFile, jsFilePath string, sour
 		return
 	}
 
-	emitContext := printer.NewEmitContext()
+	emitContext, putEmitContext := printer.GetEmitContext()
+	defer putEmitContext()
+
 	for _, transformer := range getScriptTransformers(emitContext, e.host, sourceFile) {
 		sourceFile = transformer.TransformSourceFile(sourceFile)
 	}
@@ -175,7 +177,8 @@ func (e *emitter) emitDeclarationFile(sourceFile *ast.SourceFile, declarationFil
 	}
 
 	var diags []*ast.Diagnostic
-	emitContext := printer.NewEmitContext()
+	emitContext, putEmitContext := printer.GetEmitContext()
+	defer putEmitContext()
 	for _, transformer := range e.getDeclarationTransformers(emitContext, sourceFile, declarationFilePath, declarationMapPath) {
 		sourceFile = transformer.TransformSourceFile(sourceFile)
 		diags = append(diags, transformer.GetDiagnostics()...)

internal/printer/emitcontext.go

@@ -3,6 +3,7 @@ package printer
 import (
 	"maps"
 	"slices"
+	"sync"
 	"sync/atomic"
 
 	"github.com/microsoft/typescript-go/internal/ast"
@@ -37,6 +38,20 @@ func NewEmitContext() *EmitContext {
 	return c
 }
 
+var emitContextPool = sync.Pool{
+	New: func() any {
+		return NewEmitContext()
+	},
+}
+
+func GetEmitContext() (*EmitContext, func()) {
+	c := emitContextPool.Get().(*EmitContext)
+	return c, func() {
+		c.Reset()
+		emitContextPool.Put(c)
+	}
+}
+
 func (c *EmitContext) Reset() {
 	*c = EmitContext{
 		Factory: c.Factory,

internal/testutil/tsbaseline/type_symbol_baseline.go

@@ -347,7 +347,8 @@ func (walker *typeWriterWalker) writeTypeOrSymbol(node *ast.Node, isSymbolWalk b
 	fileChecker, done := walker.getTypeCheckerForCurrentFile()
 	defer done()
 
-	ctx := printer.NewEmitContext()
+	ctx, putCtx := printer.GetEmitContext()
+	defer putCtx()
 
 	if !isSymbolWalk {
 		// Don't try to get the type of something that's already a type.