cmd/go: merge module support from x/vgo repo

This CL corresponds to CL 123361, the final manual CL in that repo,
making this the final manual sync.

All future commits will happen in this repo (the main Go repo),
and we'll update x/vgo automatically with a fixed patch+script.

Change-Id: I572243309c1809727604fd704705a23c30e85d1a
Reviewed-on: https://go-review.googlesource.com/123576
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

1 files changed, 106 insertions, 0 deletions

diff --git a/src/cmd/go/internal/modload/search.go b/src/cmd/go/internal/modload/search.go
new file mode 100644
index 0000000000..9ce65f0511
--- /dev/null
+++ b/src/cmd/go/internal/modload/search.go
@@ -0,0 +1,106 @@
+// Copyright 2018 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 modload
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"cmd/go/internal/base"
+	"cmd/go/internal/cfg"
+	"cmd/go/internal/imports"
+	"cmd/go/internal/module"
+	"cmd/go/internal/search"
+)
+
+// matchPackages returns a list of packages in the list of modules
+// matching the pattern. Package loading assumes the given set of tags.
+func matchPackages(pattern string, tags map[string]bool, modules []module.Version) []string {
+	match := func(string) bool { return true }
+	treeCanMatch := func(string) bool { return true }
+	if !search.IsMetaPackage(pattern) {
+		match = search.MatchPattern(pattern)
+		treeCanMatch = search.TreeCanMatchPattern(pattern)
+	}
+
+	have := map[string]bool{
+		"builtin": true, // ignore pseudo-package that exists only for documentation
+	}
+	if !cfg.BuildContext.CgoEnabled {
+		have["runtime/cgo"] = true // ignore during walk
+	}
+	var pkgs []string
+
+	for _, mod := range modules {
+		if !treeCanMatch(mod.Path) {
+			continue
+		}
+		var root string
+		if mod.Version == "" {
+			root = ModRoot
+		} else {
+			var err error
+			root, _, err = fetch(mod)
+			if err != nil {
+				base.Errorf("go: %v", err)
+				continue
+			}
+		}
+		root = filepath.Clean(root)
+
+		filepath.Walk(root, func(path string, fi os.FileInfo, err error) error {
+			if err != nil {
+				return nil
+			}
+
+			want := true
+			// Avoid .foo, _foo, and testdata directory trees.
+			_, elem := filepath.Split(path)
+			if strings.HasPrefix(elem, ".") || strings.HasPrefix(elem, "_") || elem == "testdata" {
+				want = false
+			}
+
+			name := mod.Path + filepath.ToSlash(path[len(root):])
+			if !treeCanMatch(name) {
+				want = false
+			}
+
+			if !fi.IsDir() {
+				if fi.Mode()&os.ModeSymlink != 0 && want {
+					if target, err := os.Stat(path); err == nil && target.IsDir() {
+						fmt.Fprintf(os.Stderr, "warning: ignoring symlink %s\n", path)
+					}
+				}
+				return nil
+			}
+
+			if !want {
+				return filepath.SkipDir
+			}
+			if path != root {
+				if _, err := os.Stat(filepath.Join(path, "go.mod")); err == nil {
+					return filepath.SkipDir
+				}
+			}
+
+			if !have[name] {
+				have[name] = true
+				if match(name) {
+					if _, _, err := scanDir(path, tags); err != imports.ErrNoGo {
+						pkgs = append(pkgs, name)
+					}
+				}
+			}
+
+			if elem == "vendor" {
+				return filepath.SkipDir
+			}
+			return nil
+		})
+	}
+	return pkgs
+}