go/types: automatically ignore $GOROOT/test files that contain build tags

These files were already ignored via a hard-coded list of excluded files.
Instead of trying to interpret the build tags for these (few) files,
recognize the tags automatically and continue to exclude them.

Fixes #10370.

Change-Id: If7a112ede02e3fa90afe303473d9ea51c5c6609d
Reviewed-on: https://go-review.googlesource.com/c/144457
Reviewed-by: Alan Donovan <adonovan@google.com>

diff --git a/src/go/types/stdlib_test.go b/src/go/types/stdlib_test.go
index 229d2030995b6a270e93e1513ea689a8463853b1..84908fd190c4eedb6a709423e59ae3339ac8b8ab 100644 (file)
--- a/src/go/types/stdlib_test.go
+++ b/src/go/types/stdlib_test.go
@@ -46,8 +46,11 @@ func TestStdlib(t *testing.T) {
        }
 }
 
-// firstComment returns the contents of the first comment in
-// the given file, assuming there's one within the first KB.
+// firstComment returns the contents of the first non-empty comment in
+// the given file, "skip", or the empty string. No matter the present
+// comments, if any of them contains a build tag, the result is always
+// "skip". Only comments before the "package" token and within the first
+// 4K of the file are considered.
 func firstComment(filename string) string {
        f, err := os.Open(filename)
        if err != nil {
@@ -55,11 +58,12 @@ func firstComment(filename string) string {
        }
        defer f.Close()
 
-       var src [1 << 10]byte // read at most 1KB
+       var src [4 << 10]byte // read at most 4KB
        n, _ := f.Read(src[:])
 
+       var first string
        var s scanner.Scanner
-       s.Init(fset.AddFile("", fset.Base(), n), src[:n], nil, scanner.ScanComments)
+       s.Init(fset.AddFile("", fset.Base(), n), src[:n], nil /* ignore errors */, scanner.ScanComments)
        for {
                _, tok, lit := s.Scan()
                switch tok {
@@ -68,9 +72,17 @@ func firstComment(filename string) string {
                        if lit[1] == '*' {
                                lit = lit[:len(lit)-2]
                        }
-                       return strings.TrimSpace(lit[2:])
-               case token.EOF:
-                       return ""
+                       contents := strings.TrimSpace(lit[2:])
+                       if strings.HasPrefix(contents, "+build ") {
+                               return "skip"
+                       }
+                       if first == "" {
+                               first = contents // contents may be "" but that's ok
+                       }
+                       // continue as we may still see build tags
+
+               case token.PACKAGE, token.EOF:
+                       return first
                }
        }
 }
@@ -142,15 +154,8 @@ func TestStdTest(t *testing.T) {
                t.Skip("skipping in short mode")
        }
 
-       // test/recover4.go is only built for Linux and Darwin.
-       // TODO(gri) Remove once tests consider +build tags (issue 10370).
-       if runtime.GOOS != "linux" && runtime.GOOS != "darwin" {
-               return
-       }
-
        testTestDir(t, filepath.Join(runtime.GOROOT(), "test"),
                "cmplxdivide.go", // also needs file cmplxdivide1.go - ignore
-               "sigchld.go",     // don't work on Windows; testTestDir should consult build tags
        )
 }
 
@@ -166,7 +171,6 @@ func TestStdFixed(t *testing.T) {
                "issue6889.go",   // gc-specific test
                "issue7746.go",   // large constants - consumes too much memory
                "issue11362.go",  // canonical import path check
-               "issue15002.go",  // uses Mmap; testTestDir should consult build tags
                "issue16369.go",  // go/types handles this correctly - not an issue
                "issue18459.go",  // go/types doesn't check validity of //go:xxx directives
                "issue18882.go",  // go/types doesn't check validity of //go:xxx directives