go/buildutil: call ReadDir via the build.Context's file system interface

LGTM=gri
R=gri, crawshaw
CC=golang-codereviews
https://golang.org/cl/171920043

go/buildutil/allpackages.go

@@ -4,11 +4,13 @@
 
 // Package buildutil provides utilities related to the go/build
 // package in the standard library.
+//
+// All I/O is done via the build.Context file system interface, which must
+// be concurrency-safe.
 package buildutil
 
 import (
 	"go/build"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"sort"
@@ -23,7 +25,7 @@ import (
 // The result may include import paths for directories that contain no
 // *.go files, such as "archive" (in $GOROOT/src).
 //
-// All I/O is via the build.Context virtual file system,
+// All I/O is done via the build.Context file system interface,
 // which must be concurrency-safe.
 //
 func AllPackages(ctxt *build.Context) []string {
@@ -45,7 +47,7 @@ func AllPackages(ctxt *build.Context) []string {
 // If the package directory exists but could not be read, the second
 // argument to the found function provides the error.
 //
-// The found function and the build.Context virtual file system
+// The found function and the build.Context file system interface
 // accessors must be concurrency safe.
 //
 func ForEachPackage(ctxt *build.Context, found func(importPath string, err error)) {
@@ -66,11 +68,6 @@ func ForEachPackage(ctxt *build.Context, found func(importPath string, err error
 }
 
 func allPackages(ctxt *build.Context, sema chan bool, root string, found func(string, error)) {
-	ReadDir := ctxt.ReadDir
-	if ReadDir == nil {
-		ReadDir = ioutil.ReadDir
-	}
-
 	root = filepath.Clean(root) + string(os.PathSeparator)
 
 	var wg sync.WaitGroup
@@ -92,7 +89,7 @@ func allPackages(ctxt *build.Context, sema chan bool, root string, found func(st
 		}
 
 		sema <- true
-		files, err := ReadDir(dir)
+		files, err := ReadDir(ctxt, dir)
 		<-sema
 		if pkg != "" || err != nil {
 			found(pkg, err)

go/buildutil/util.go

@@ -11,6 +11,7 @@ import (
 	"go/parser"
 	"go/token"
 	"io"
+	"io/ioutil"
 	"os"
 	"path"
 	"path/filepath"
@@ -18,7 +19,7 @@ import (
 )
 
 // ParseFile behaves like parser.ParseFile,
-// but uses the build context's virtual file system, if any.
+// but uses the build context's file system interface, if any.
 //
 // If file is not absolute (as defined by IsAbsPath), the (dir, file)
 // components are joined using JoinPath; dir must be absolute.
@@ -46,7 +47,7 @@ func ParseFile(fset *token.FileSet, ctxt *build.Context, displayPath func(string
 // ContainingPackage returns the package containing filename.
 //
 // If filename is not absolute, it is interpreted relative to working directory dir.
-// All I/O is via the build context's virtual file system, if any.
+// All I/O is via the build context's file system interface, if any.
 //
 // The '...Files []string' fields of the resulting build.Package are not
 // populated (build.FindOnly mode).
@@ -58,12 +59,12 @@ func ContainingPackage(ctxt *build.Context, dir, filename string) (*build.Packag
 		filename = JoinPath(ctxt, dir, filename)
 	}
 
-	// We must not assume the virtualized file tree uses
+	// We must not assume the file tree uses
 	// "/" always,
 	// `\` always,
 	// or os.PathSeparator (which varies by platform),
 	// but to make any progress, we are forced to assume that
-	// virtualized paths will not use `\` unless the PathSeparator
+	// paths will not use `\` unless the PathSeparator
 	// is also `\`, thus we can rely on filepath.ToSlash for some sanity.
 
 	dirSlash := path.Dir(filepath.ToSlash(filename)) + "/"
@@ -80,10 +81,14 @@ func ContainingPackage(ctxt *build.Context, dir, filename string) (*build.Packag
 	return nil, fmt.Errorf("can't find package containing %s", filename)
 }
 
-// -- Effective methods of virtual file system -------------------------
+// -- Effective methods of file system interface -------------------------
+
+// (go/build.Context defines these as methods, but does not export them.)
+
+// TODO(adonovan): HasSubdir?
 
 // FileExists returns true if the specified file exists,
-// using the build context's virtual file system.
+// using the build context's file system interface.
 func FileExists(ctxt *build.Context, path string) bool {
 	if ctxt.OpenFile != nil {
 		r, err := ctxt.OpenFile(path)
@@ -98,7 +103,7 @@ func FileExists(ctxt *build.Context, path string) bool {
 }
 
 // OpenFile behaves like os.Open,
-// but uses the build context's virtual file system, if any.
+// but uses the build context's file system interface, if any.
 func OpenFile(ctxt *build.Context, path string) (io.ReadCloser, error) {
 	if ctxt.OpenFile != nil {
 		return ctxt.OpenFile(path)
@@ -107,7 +112,7 @@ func OpenFile(ctxt *build.Context, path string) (io.ReadCloser, error) {
 }
 
 // IsAbsPath behaves like filepath.IsAbs,
-// but uses the build context's virtual file system, if any.
+// but uses the build context's file system interface, if any.
 func IsAbsPath(ctxt *build.Context, path string) bool {
 	if ctxt.IsAbsPath != nil {
 		return ctxt.IsAbsPath(path)
@@ -116,7 +121,7 @@ func IsAbsPath(ctxt *build.Context, path string) bool {
 }
 
 // JoinPath behaves like filepath.Join,
-// but uses the build context's virtual file system.
+// but uses the build context's file system interface, if any.
 func JoinPath(ctxt *build.Context, path ...string) string {
 	if ctxt.JoinPath != nil {
 		return ctxt.JoinPath(path...)
@@ -124,4 +129,30 @@ func JoinPath(ctxt *build.Context, path ...string) string {
 	return filepath.Join(path...)
 }
 
-// TODO(adonovan): SplitPathList, IsDir, HasSubdir, ReadDir?
+// IsDir behaves like os.Stat plus IsDir,
+// but uses the build context's file system interface, if any.
+func IsDir(ctxt *build.Context, path string) bool {
+	if ctxt.IsDir != nil {
+		return ctxt.IsDir(path)
+	}
+	fi, err := os.Stat(path)
+	return err == nil && fi.IsDir()
+}
+
+// ReadDir behaves like ioutil.ReadDir,
+// but uses the build context's file system interface, if any.
+func ReadDir(ctxt *build.Context, path string) ([]os.FileInfo, error) {
+	if ctxt.ReadDir != nil {
+		return ctxt.ReadDir(path)
+	}
+	return ioutil.ReadDir(path)
+}
+
+// SplitPathList behaves like filepath.SplitList,
+// but uses the build context's file system interface, if any.
+func SplitPathList(ctxt *build.Context, s string) []string {
+	if ctxt.SplitPathList != nil {
+		return ctxt.SplitPathList(s)
+	}
+	return filepath.SplitList(s)
+}