1 files changed, 194 insertions, 0 deletions
diff --git a/src/pkg/go/printer/printer_test.go b/src/pkg/go/printer/printer_test.go
new file mode 100644
index 000000000..ff2d906b5
--- /dev/null
+++ b/src/pkg/go/printer/printer_test.go
@@ -0,0 +1,194 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package printer
+
+import (
+	"bytes"
+	"flag"
+	"io/ioutil"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"path/filepath"
+	"testing"
+	"time"
+)
+
+const (
+	dataDir  = "testdata"
+	tabwidth = 8
+)
+
+var update = flag.Bool("update", false, "update golden files")
+
+var fset = token.NewFileSet()
+
+func lineString(text []byte, i int) string {
+	i0 := i
+	for i < len(text) && text[i] != '\n' {
+		i++
+	}
+	return string(text[i0:i])
+}
+
+type checkMode uint
+
+const (
+	export checkMode = 1 << iota
+	rawFormat
+)
+
+func runcheck(t *testing.T, source, golden string, mode checkMode) {
+	// parse source
+	prog, err := parser.ParseFile(fset, source, nil, parser.ParseComments)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	// filter exports if necessary
+	if mode&export != 0 {
+		ast.FileExports(prog) // ignore result
+		prog.Comments = nil   // don't print comments that are not in AST
+	}
+
+	// determine printer configuration
+	cfg := Config{Tabwidth: tabwidth}
+	if mode&rawFormat != 0 {
+		cfg.Mode |= RawFormat
+	}
+
+	// format source
+	var buf bytes.Buffer
+	if _, err := cfg.Fprint(&buf, fset, prog); err != nil {
+		t.Error(err)
+	}
+	res := buf.Bytes()
+
+	// update golden files if necessary
+	if *update {
+		if err := ioutil.WriteFile(golden, res, 0644); err != nil {
+			t.Error(err)
+		}
+		return
+	}
+
+	// get golden
+	gld, err := ioutil.ReadFile(golden)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+
+	// compare lengths
+	if len(res) != len(gld) {
+		t.Errorf("len = %d, expected %d (= len(%s))", len(res), len(gld), golden)
+	}
+
+	// compare contents
+	for i, line, offs := 0, 1, 0; i < len(res) && i < len(gld); i++ {
+		ch := res[i]
+		if ch != gld[i] {
+			t.Errorf("%s:%d:%d: %s", source, line, i-offs+1, lineString(res, offs))
+			t.Errorf("%s:%d:%d: %s", golden, line, i-offs+1, lineString(gld, offs))
+			t.Error()
+			return
+		}
+		if ch == '\n' {
+			line++
+			offs = i + 1
+		}
+	}
+}
+
+func check(t *testing.T, source, golden string, mode checkMode) {
+	// start a timer to produce a time-out signal
+	tc := make(chan int)
+	go func() {
+		time.Sleep(10e9) // plenty of a safety margin, even for very slow machines
+		tc <- 0
+	}()
+
+	// run the test
+	cc := make(chan int)
+	go func() {
+		runcheck(t, source, golden, mode)
+		cc <- 0
+	}()
+
+	// wait for the first finisher
+	select {
+	case <-tc:
+		// test running past time out
+		t.Errorf("%s: running too slowly", source)
+	case <-cc:
+		// test finished within alloted time margin
+	}
+}
+
+type entry struct {
+	source, golden string
+	mode           checkMode
+}
+
+// Use gotest -update to create/update the respective golden files.
+var data = []entry{
+	{"empty.input", "empty.golden", 0},
+	{"comments.input", "comments.golden", 0},
+	{"comments.input", "comments.x", export},
+	{"linebreaks.input", "linebreaks.golden", 0},
+	{"expressions.input", "expressions.golden", 0},
+	{"expressions.input", "expressions.raw", rawFormat},
+	{"declarations.input", "declarations.golden", 0},
+	{"statements.input", "statements.golden", 0},
+	{"slow.input", "slow.golden", 0},
+}
+
+func TestFiles(t *testing.T) {
+	for i, e := range data {
+		source := filepath.Join(dataDir, e.source)
+		golden := filepath.Join(dataDir, e.golden)
+		check(t, source, golden, e.mode)
+		// TODO(gri) check that golden is idempotent
+		//check(t, golden, golden, e.mode)
+		if testing.Short() && i >= 3 {
+			break
+		}
+	}
+}
+
+// TestLineComments, using a simple test case, checks that consequtive line
+// comments are properly terminated with a newline even if the AST position
+// information is incorrect.
+//
+func TestLineComments(t *testing.T) {
+	const src = `// comment 1
+	// comment 2
+	// comment 3
+	package main
+	`
+
+	fset := token.NewFileSet()
+	ast1, err1 := parser.ParseFile(fset, "", src, parser.ParseComments)
+	if err1 != nil {
+		panic(err1)
+	}
+
+	var buf bytes.Buffer
+	fset = token.NewFileSet() // use the wrong file set
+	Fprint(&buf, fset, ast1)
+
+	nlines := 0
+	for _, ch := range buf.Bytes() {
+		if ch == '\n' {
+			nlines++
+		}
+	}
+
+	const expected = 3
+	if nlines < expected {
+		t.Errorf("got %d, expected %d\n", nlines, expected)
+	}
+}