Add readFile template func

This also includes a refactor of the hugofs package and its usage.

The motivation for that is:

The Afero filesystems are brilliant. Hugo's way of adding a dozen of global variables for the different filesystems was a mistake. In readFile (and also in some other places in Hugo today) we need a way to restrict the access inside the working dir. We could use ioutil.ReadFile and implement the path checking, checking the base path and the dots ("..") etc. But it is obviously better to use an Afero BasePathFs combined witha ReadOnlyFs. We could create a use-once-filesystem and handle the initialization ourselves, but since this is also useful to others and the initialization depends on some other global state (which would mean to create a new file system on every invocation), we might as well do it properly and encapsulate the predefined set of filesystems. This change also leads the way, if needed, to encapsulate the file systems in a struct, making it possible to have several file system sets in action at once (parallel multilanguage site building? With Moore's law and all...)

Fixes #1551

1 files changed, 78 insertions, 5 deletions

diff --git a/hugofs/fs.go b/hugofs/fs.go
index 7807bf935..a3cb55ea1 100644
--- a/hugofs/fs.go
+++ b/hugofs/fs.go
@@ -1,4 +1,4 @@
-// Copyright 2015 The Hugo Authors. All rights reserved.
+// Copyright 2016 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -13,8 +13,81 @@
 
 package hugofs
 
-import "github.com/spf13/afero"
+import (
+	"github.com/spf13/afero"
+	"github.com/spf13/viper"
+)
 
-var SourceFs afero.Fs = new(afero.OsFs)
-var DestinationFS afero.Fs = new(afero.OsFs)
-var OsFs afero.Fs = new(afero.OsFs)
+var (
+	sourceFs      afero.Fs
+	destinationFs afero.Fs
+	osFs          afero.Fs = &afero.OsFs{}
+	workingDirFs  *afero.BasePathFs
+)
+
+// Source returns Hugo's source file system.
+func Source() afero.Fs {
+	return sourceFs
+}
+
+// SetSource sets Hugo's source file system
+// and re-initializes dependent file systems.
+func SetSource(fs afero.Fs) {
+	sourceFs = fs
+	initSourceDependencies()
+}
+
+// Destination returns Hugo's destionation file system.
+func Destination() afero.Fs {
+	return destinationFs
+}
+
+// SetDestination sets Hugo's destionation file system
+func SetDestination(fs afero.Fs) {
+	destinationFs = fs
+}
+
+// Os returns an OS file system.
+func Os() afero.Fs {
+	return osFs
+}
+
+// WorkingDir returns a read-only file system
+// restricted to the project working dir.
+func WorkingDir() *afero.BasePathFs {
+	return workingDirFs
+}
+
+// InitFs initializes with the OS file system
+// as source and destination file systems.
+func InitDefaultFs() {
+	InitFs(&afero.OsFs{})
+}
+
+// InitMemFs initializes with a MemMapFs as source and destination file systems.
+// Useful for testing.
+func InitMemFs() {
+	InitFs(&afero.MemMapFs{})
+}
+
+// InitFs initializes with the given file system
+// as source and destination file systems.
+func InitFs(fs afero.Fs) {
+	sourceFs = fs
+	destinationFs = fs
+
+	initSourceDependencies()
+}
+
+func initSourceDependencies() {
+	workingDir := viper.GetString("WorkingDir")
+
+	if workingDir != "" {
+		workingDirFs = afero.NewBasePathFs(afero.NewReadOnlyFs(sourceFs), workingDir).(*afero.BasePathFs)
+	}
+
+}
+
+func init() {
+	InitDefaultFs()
+}