util: safepath: Add a new safe path helper library

This is a new path manipulation library that is designed to be safer
than using simple strings for everything. It is more work to use, but it
can help you keep track of the different path types.

It has been sitting unused in a git branch for too long, and I figured
it should see the light of day in case someone wants to start using it.

util/safepath/interface_test.go

@@ -0,0 +1,116 @@
+// Mgmt
+// Copyright (C) 2013-2021+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package safepath_test
+
+import (
+	"testing"
+
+	"github.com/purpleidea/mgmt/util/safepath"
+)
+
+type badPath struct{}
+
+func (obj badPath) String() string { return "" }
+func (obj badPath) Path() string   { return "" }
+func (obj badPath) IsDir() bool    { return false }
+func (obj badPath) IsAbs() bool    { return false }
+func (obj badPath) isPath()        {} // can't be the same as in the Path interface!
+
+func TestInterfaces(t *testing.T) {
+
+	absFile, err := safepath.ParseIntoAbsFile("/foo/bar/abs/file")
+	if err != nil {
+		t.Errorf("err: %+v", err)
+		return
+	}
+
+	absDir, err := safepath.ParseIntoAbsDir("/foo/bar/abs/dir/")
+	if err != nil {
+		t.Errorf("err: %+v", err)
+		return
+	}
+
+	relFile, err := safepath.ParseIntoRelFile("foo/bar/rel/file")
+	if err != nil {
+		t.Errorf("err: %+v", err)
+		return
+	}
+
+	relDir, err := safepath.ParseIntoRelDir("foo/bar/rel/dir/")
+	if err != nil {
+		t.Errorf("err: %+v", err)
+		return
+	}
+
+	var p safepath.Path
+	p = absFile
+	p = absDir
+	p = relFile
+	p = relDir
+	//p = badPath{} // nope
+	_ = p
+
+	var f safepath.File
+	f = absFile
+	//f = absDir // nope
+	f = relFile
+	//f = relDir // nope
+	_ = f
+
+	var d safepath.Dir
+	//d = absFile // nope
+	d = absDir
+	//d = relFile // nope
+	d = relDir
+	_ = d
+
+	var a safepath.Abs
+	a = absFile
+	a = absDir
+	//a = relFile // nope
+	//a = relDir // nope
+	_ = a
+
+	var r safepath.Rel
+	//r = absFile // nope
+	//r = absDir // nope
+	r = relFile
+	r = relDir
+	_ = r
+}
+
+func TestParse(t *testing.T) {
+	path, err := safepath.ParseIntoPath("/foo/bar/abs/file", false)
+	if err != nil {
+		t.Errorf("err: %+v", err)
+		return
+	}
+
+	if _, ok := path.(safepath.AbsFile); !ok {
+		t.Errorf("expected AbsFile, got: %T", path)
+	}
+	if _, ok := path.(safepath.AbsDir); ok {
+		t.Errorf("unexpected AbsDir")
+	}
+	if _, ok := path.(safepath.RelFile); ok {
+		t.Errorf("unexpected RelFile")
+	}
+	if _, ok := path.(safepath.RelDir); ok {
+		t.Errorf("unexpected RelDir")
+	}
+}