lang: Initial implementation of the mgmt language

This is an initial implementation of the mgmt language. It is a
declarative (immutable) functional, reactive, domain specific
programming language. It is intended to be a language that is:

* safe
* powerful
* easy to reason about

With these properties, we hope this language, and the mgmt engine will
allow you to model the real-time systems that you'd like to automate.

This also includes a number of other associated changes. Sorry for the
large size of this patch.

lang/funcs/facts/func_test.go

@@ -0,0 +1,97 @@
+// Mgmt
+// Copyright (C) 2013-2018+ 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 facts
+
+import (
+	"log"
+	"testing"
+	"time"
+
+	"github.com/purpleidea/mgmt/lang/funcs"
+	"github.com/purpleidea/mgmt/pgraph"
+)
+
+const Debug = false // switch on for more interactive log messages when testing!
+
+// logf switches messages to use realtime logging when debugging tests, and the
+// quiet logging which is not shown until test failures, when debug mode is off.
+func logf(t *testing.T, format string, args ...interface{}) {
+	if Debug {
+		log.Printf(format, args...)
+	} else {
+		t.Logf(format, args...)
+	}
+}
+
+func TestFuncGraph0(t *testing.T) {
+	logf(t, "Hello!")
+	g, _ := pgraph.NewGraph("empty") // empty graph
+
+	obj := &funcs.Engine{
+		Graph: g,
+	}
+
+	logf(t, "Init...")
+	if err := obj.Init(); err != nil {
+		t.Errorf("could not init: %+v", err)
+		return
+	}
+
+	logf(t, "Validate...")
+	if err := obj.Validate(); err != nil {
+		t.Errorf("could not validate: %+v", err)
+		return
+	}
+
+	logf(t, "Run...")
+	if err := obj.Run(); err != nil {
+		t.Errorf("could not run: %+v", err)
+		return
+	}
+
+	// wait for some activity
+	logf(t, "Stream...")
+	stream := obj.Stream()
+	logf(t, "Loop...")
+	br := time.After(time.Duration(5) * time.Second)
+Loop:
+	for {
+		select {
+		case err, ok := <-stream:
+			if !ok {
+				logf(t, "Stream break...")
+				break Loop
+			}
+			if err != nil {
+				logf(t, "Error: %+v", err)
+				continue
+			}
+
+		case <-br:
+			logf(t, "Break...")
+			t.Errorf("empty graph should have closed stream")
+			break Loop
+		}
+	}
+
+	logf(t, "Closing...")
+	if err := obj.Close(); err != nil {
+		t.Errorf("could not close: %+v", err)
+		return
+	}
+}