lang: Add a test for duplicate functions called

We should not call either of these functions more than once for their
values. If we do, it means we have made a mistake with a compiler
optimization.

This is important, because otherwise if you had code like:

$x = random_password()

Then this would obviously be a problem. Thankfully, the situations where
functions generate unique data is rare, but it's probably something we
should take care of.

lang/funcs/core/test/oneinstance_fact.go

@@ -0,0 +1,123 @@
+// 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"
+	"sync"
+
+	"github.com/purpleidea/mgmt/lang/funcs/facts"
+	"github.com/purpleidea/mgmt/lang/funcs/simple"
+	"github.com/purpleidea/mgmt/lang/types"
+)
+
+const (
+	// OneInstanceAFuncName 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.
+	OneInstanceAFuncName = "one_instance_a"
+
+	// OneInstanceBFuncName 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.
+	OneInstanceBFuncName = "one_instance_b"
+
+	msg = "hello"
+)
+
+func init() {
+	oneInstanceAMutex = &sync.Mutex{}
+	oneInstanceBMutex = &sync.Mutex{}
+
+	facts.ModuleRegister(ModuleName, OneInstanceAFuncName, func() facts.Fact { return &OneInstanceFact{} }) // must register the fact and name
+
+	simple.ModuleRegister(ModuleName, OneInstanceBFuncName, &types.FuncValue{
+		T: types.NewType("func() str"),
+		V: func([]types.Value) (types.Value, error) {
+			oneInstanceBMutex.Lock()
+			if oneInstanceBFlag {
+				panic("should not get called twice")
+			}
+			oneInstanceBFlag = true
+			oneInstanceBMutex.Unlock()
+			return &types.StrValue{V: msg}, nil
+		},
+	})
+}
+
+var (
+	oneInstanceAFlag  bool
+	oneInstanceBFlag  bool
+	oneInstanceAMutex *sync.Mutex
+	oneInstanceBMutex *sync.Mutex
+)
+
+// OneInstanceFact is a fact which flips a bool repeatedly. This is an example
+// fact and is not meant for serious computing. This would be better served by a
+// flip function which you could specify an interval for.
+type OneInstanceFact 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 *OneInstanceFact) String() string {
+	return OneInstanceAFuncName
+}
+
+// Validate makes sure we've built our struct properly. It is usually unused for
+// normal facts that users can use directly.
+//func (obj *OneInstanceFact) Validate() error {
+//	return nil
+//}
+
+// Info returns some static info about itself.
+func (obj *OneInstanceFact) Info() *facts.Info {
+	return &facts.Info{
+		Output: types.NewType("str"),
+	}
+}
+
+// Init runs some startup code for this fact.
+func (obj *OneInstanceFact) Init(init *facts.Init) error {
+	obj.init = init
+	obj.init.Logf("Init of `%s` @ %p", OneInstanceAFuncName, obj)
+
+	oneInstanceAMutex.Lock()
+	if oneInstanceAFlag {
+		panic("should not get called twice")
+	}
+	oneInstanceAFlag = true
+	oneInstanceAMutex.Unlock()
+	return nil
+}
+
+// Stream returns the changing values that this fact has over time.
+func (obj *OneInstanceFact) Stream(ctx context.Context) error {
+	obj.init.Logf("Stream of `%s` @ %p", OneInstanceAFuncName, obj)
+	defer close(obj.init.Output) // always signal when we're done
+	select {
+	case obj.init.Output <- &types.StrValue{
+		V: msg,
+	}:
+	case <-ctx.Done():
+		return nil
+	}
+
+	return nil
+}

lang/interpret_test/TestAstFunc2/test-one-instance.txtar

@@ -0,0 +1,24 @@
+-- main.mcl --
+import "test"
+# one_instance_a should only produce one value, and will error if initialized twice
+$x = test.one_instance_a()
+test "test1" {
+	anotherstr => $x,
+}
+test "test2" {
+	anotherstr => $x,
+}
+
+# one_instance_b should only produce one value, and will error if initialized twice
+$y = test.one_instance_b()
+test "test3" {
+	anotherstr => $y,
+}
+test "test4" {
+	anotherstr => $y,
+}
+-- OUTPUT --
+Vertex: test[test1]
+Vertex: test[test2]
+Vertex: test[test3]
+Vertex: test[test4]