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

src/pkg/go/build/build_test.go

Index: src/pkg/go/build/build_test.go
===================================================================
--- a/src/pkg/go/build/build_test.go
+++ b/src/pkg/go/build/build_test.go
@@ -75,3 +75,32 @@
 		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")
+	}
+}