performance_test.go

Documentation: go/printer

		 1  // Copyright 2009 The Go Authors. All rights reserved.
		 2  // Use of this source code is governed by a BSD-style
		 3  // license that can be found in the LICENSE file.
		 4  
		 5  // This file implements a simple printer performance benchmark:
		 6  // go test -bench=BenchmarkPrint
		 7  
		 8  package printer
		 9  
		10  import (
		11  	"bytes"
		12  	"go/ast"
		13  	"go/parser"
		14  	"io"
		15  	"log"
		16  	"os"
		17  	"testing"
		18  )
		19  
		20  var testfile *ast.File
		21  
		22  func testprint(out io.Writer, file *ast.File) {
		23  	if err := (&Config{TabIndent | UseSpaces | normalizeNumbers, 8, 0}).Fprint(out, fset, file); err != nil {
		24  		log.Fatalf("print error: %s", err)
		25  	}
		26  }
		27  
		28  // cannot initialize in init because (printer) Fprint launches goroutines.
		29  func initialize() {
		30  	const filename = "testdata/parser.go"
		31  
		32  	src, err := os.ReadFile(filename)
		33  	if err != nil {
		34  		log.Fatalf("%s", err)
		35  	}
		36  
		37  	file, err := parser.ParseFile(fset, filename, src, parser.ParseComments)
		38  	if err != nil {
		39  		log.Fatalf("%s", err)
		40  	}
		41  
		42  	var buf bytes.Buffer
		43  	testprint(&buf, file)
		44  	if !bytes.Equal(buf.Bytes(), src) {
		45  		log.Fatalf("print error: %s not idempotent", filename)
		46  	}
		47  
		48  	testfile = file
		49  }
		50  
		51  func BenchmarkPrint(b *testing.B) {
		52  	if testfile == nil {
		53  		initialize()
		54  	}
		55  	for i := 0; i < b.N; i++ {
		56  		testprint(io.Discard, testfile)
		57  	}
		58  }
		59
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