lang: funcs: core: test: Add a new test functions package

This adds a new test functions package and also a new "fastcount"
function which counts up from zero as fast as is possible. You probably
don't want to use this in production, but it is useful for performance
and deadlock testing the resource and function engines.

examples/lang/fastcount.mcl

@@ -0,0 +1,32 @@
+import "fmt"
+import "test"
+
+# XXX: Because our function engine is not synchronous, absurdly-fast function
+# changing will result in these four files having vastly different values after
+# a certain amount of time. We probably want to fix this eventually.
+$count = test.fastcount()
+
+file "/tmp/mgmt-count0" {
+	content => fmt.printf("count is: %d\n", $count + 0),
+	state => $const.res.file.state.exists,
+}
+
+file "/tmp/mgmt-count1" {
+	content => fmt.printf("count is: %d\n", $count + 1),
+	state => $const.res.file.state.exists,
+}
+
+file "/tmp/mgmt-count2" {
+	content => fmt.printf("count is: %d\n", $count + 2),
+	state => $const.res.file.state.exists,
+}
+
+file "/tmp/mgmt-count" {
+	content => fmt.printf("count is: %d\n", $count),
+	state => $const.res.file.state.exists,
+}
+
+File["/tmp/mgmt-count0"] -> File["/tmp/mgmt-count1"]
+File["/tmp/mgmt-count0"] -> File["/tmp/mgmt-count2"]
+File["/tmp/mgmt-count1"] -> File["/tmp/mgmt-count"]
+File["/tmp/mgmt-count2"] -> File["/tmp/mgmt-count"]

lang/funcs/core/core.go

@@ -35,6 +35,7 @@ import (
 	_ "github.com/purpleidea/mgmt/lang/funcs/core/regexp"
 	_ "github.com/purpleidea/mgmt/lang/funcs/core/strings"
 	_ "github.com/purpleidea/mgmt/lang/funcs/core/sys"
+	_ "github.com/purpleidea/mgmt/lang/funcs/core/test"
 	_ "github.com/purpleidea/mgmt/lang/funcs/core/world"
 )
 

lang/funcs/core/test/fastcount_fact.go

@@ -0,0 +1,83 @@
+// Mgmt
+// Copyright (C) 2013-2023+ 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 coretest
+
+import (
+	"context"
+
+	"github.com/purpleidea/mgmt/lang/funcs/facts"
+	"github.com/purpleidea/mgmt/lang/types"
+)
+
+const (
+	// FastCountFuncName is the name this fact is registered as. It's still a
+	// Func Name because this is the name space the fact is actually using.
+	FastCountFuncName = "fastcount"
+)
+
+func init() {
+	facts.ModuleRegister(ModuleName, FastCountFuncName, func() facts.Fact { return &FastCountFact{} }) // must register the fact and name
+}
+
+// FastCountFact is a fact that counts up as fast as possible from zero forever.
+type FastCountFact struct {
+	init *facts.Init
+}
+
+// String returns a simple name for this fact. This is needed so this struct can
+// satisfy the pgraph.Vertex interface.
+func (obj *FastCountFact) String() string {
+	return FastCountFuncName
+}
+
+// Validate makes sure we've built our struct properly. It is usually unused for
+// normal facts that users can use directly.
+//func (obj *FastCountFact) Validate() error {
+//	return nil
+//}
+
+// Info returns some static info about itself.
+func (obj *FastCountFact) Info() *facts.Info {
+	return &facts.Info{
+		Output: types.NewType("int"),
+	}
+}
+
+// Init runs some startup code for this fact.
+func (obj *FastCountFact) Init(init *facts.Init) error {
+	obj.init = init
+	return nil
+}
+
+// Stream returns the changing values that this fact has over time.
+func (obj *FastCountFact) Stream(ctx context.Context) error {
+	defer close(obj.init.Output) // always signal when we're done
+
+	count := int64(0)
+
+	// streams must generate an initial event on startup
+	for {
+		select {
+		case obj.init.Output <- &types.IntValue{V: count}:
+			count++
+
+		case <-ctx.Done():
+			return nil
+		}
+	}
+}

lang/funcs/core/test/test.go

@@ -0,0 +1,23 @@
+// Mgmt
+// Copyright (C) 2013-2023+ 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 coretest
+
+const (
+	// ModuleName is the prefix given to all the functions in this module.
+	ModuleName = "test"
+)