code review 6458091: go/build: correct shouldBuild bug reading whole content...

src/pkg/go/build/build_test.go

 // Copyright 2011 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 build
 
 import (
         "os"
         "path/filepath"
         "runtime"
@@ skipping 57 matching lines @@
         }
 
         p, err := ImportDir(cwd, 0)
         if err != nil {
                 t.Fatal(err)
         }
         if p.ImportPath != "go/build" {
                 t.Fatalf("ImportPath=%q, want %q", p.ImportPath, "go/build")
         }
 }
+
+func TestShouldBuild(t *testing.T) {
+        const file1 = "// +build tag1\n\n" +
+                "package main\n"
+
+        const file2 = "// +build cgo\n\n" +
+                "// This package implements parsing of tags like\n" +
+                "// +build tag1\n" +
+                "package build"
+
+        const file3 = "// Copyright The Go Authors.\n\n" +
+                "package build\n\n" +
+                "// shouldBuild checks tags given by lines of the form\n" +
+                "// +build tag\n" +
+                "func shouldBuild(content []byte)\n"
+
+        ctx := &Context{BuildTags: []string{"tag1"}}
+        if !ctx.shouldBuild([]byte(file1)) {
+                t.Errorf("should not build file1, expected the contrary")
+        }
+        if ctx.shouldBuild([]byte(file2)) {
+                t.Errorf("should build file2, expected the contrary")
+        }
+
+        ctx = &Context{BuildTags: nil}
+        if !ctx.shouldBuild([]byte(file3)) {
+                t.Errorf("should not build file3, expected the contrary")
+        }
+}