commit 71514c07d2dae1dfb1f8a88ff42d229288ddfc81
author Cole Faust <colefaust@google.com> Thu Jan 27 17:21:41 2022 -0800
committer Cole Faust <colefaust@google.com> Fri Jan 28 19:47:34 2022 +0000
tree b6e3f8a94f1ea37655ab43aeab8493841ffab7b9
parent 54f311d0fbbfcef663518bdca7a4b066486562f0

Remove variableDefinedExpr

VariableDefinedExpr was under-developed, and would not
take into account if a variable was from the globals
or product config dictionary.

It also always emitted `g.get("VARIABLE") != None`, which
is not correct behavior. In this example makefile:

```
MY_VAR :=

ifdef MY_VAR
$(info MY_VAR is defined)
else
$(info MY_VAR is not defined)
endif

ifdef MY_UNDEFINED_VAR
$(info MY_UNDEFINED_VAR is defined)
else
$(info MY_UNDEFINED_VAR is not defined)
endif

MY_VAR ?= true
MY_UNDEFINED_VAR ?= true


$(info MY_VAR after ?= is $(MY_VAR))
$(info MY_UNDEFINED_VAR after ?= is $(MY_UNDEFINED_VAR))


.PHONY: all
all:
	@:
```

We get the output:

MY_VAR is not defined
MY_UNDEFINED_VAR is not defined
MY_VAR after ?= is
MY_UNDEFINED_VAR after ?= is true

So we can see that even if a variable was set, it's considered
not defined if it was set to an empty value. However, ?= works
differently, and does require the != None, so that was left
as is.

Just use a variableRefExpr and rely on the fact
that variables will be truthy if they're defined.

Fixes: 216700361
Test: go test
Change-Id: If8944da2579e8658e3fc4f666b1f3b2815f8c8b1

mk2rbc/mk2rbc.go

diff --git a/mk2rbc/mk2rbc.go b/mk2rbc/mk2rbc.go
index e317cad..17d3c21 100644
--- a/mk2rbc/mk2rbc.go
+++ b/mk2rbc/mk2rbc.go
@@ -1003,19 +1003,14 @@
 	ctx.popReceiver()
 }
 
-func (ctx *parseContext) newIfDefinedNode(check *mkparser.Directive) (starlarkExpr, bool) {
-	if !check.Args.Const() {
-		return ctx.newBadExpr(check, "ifdef variable ref too complex: %s", check.Args.Dump()), false
-	}
-	v := ctx.addVariable(check.Args.Strings[0])
-	return &variableDefinedExpr{v}, true
-}
-
 func (ctx *parseContext) parseCondition(check *mkparser.Directive) starlarkNode {
 	switch check.Name {
 	case "ifdef", "ifndef", "elifdef", "elifndef":
-		v, ok := ctx.newIfDefinedNode(check)
-		if ok && strings.HasSuffix(check.Name, "ndef") {
+		if !check.Args.Const() {
+			return &exprNode{expr: ctx.newBadExpr(check, "ifdef variable ref too complex: %s", check.Args.Dump())}
+		}
+		v := NewVariableRefExpr(ctx.addVariable(check.Args.Strings[0]), false)
+		if strings.HasSuffix(check.Name, "ndef") {
 			v = &notExpr{v}
 		}
 		return &ifNode{