From 816e080c4daff4c82fc41afd369c0c250cac540f Mon Sep 17 00:00:00 2001
From: Cole Faust <colefaust@google.com>
Date: Fri, 4 Mar 2022 12:04:31 -0800
Subject: [PATCH] Call rblf.setDefault() when appending to a variable without
 +=

Bug: 222737841
Test: go test
Change-Id: I10e9e994fb1979e2e06ad30bbe66a21657d1e3db
---
 mk2rbc/mk2rbc_test.go |  1 +
 mk2rbc/variable.go    | 29 +++++++++++++++++++++--------
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/mk2rbc/mk2rbc_test.go b/mk2rbc/mk2rbc_test.go
index a162021b4..ce1a1f9b1 100644
--- a/mk2rbc/mk2rbc_test.go
+++ b/mk2rbc/mk2rbc_test.go
@@ -985,6 +985,7 @@ endif
 def init(g, handle):
   cfg = rblf.cfg(handle)
   if "hwaddress" not in cfg.get("PRODUCT_PACKAGES", []):
+    rblf.setdefault(handle, "PRODUCT_PACKAGES")
     cfg["PRODUCT_PACKAGES"] = (rblf.mkstrip("%s hwaddress" % " ".join(cfg.get("PRODUCT_PACKAGES", [])))).split()
 `,
 	},
diff --git a/mk2rbc/variable.go b/mk2rbc/variable.go
index f7adca568..73afd1923 100644
--- a/mk2rbc/variable.go
+++ b/mk2rbc/variable.go
@@ -88,20 +88,33 @@ func (pcv productConfigVariable) emitSet(gctx *generationContext, asgn *assignme
 		}
 		value.emit(gctx)
 	}
-
-	switch asgn.flavor {
-	case asgnSet:
-		emitAssignment()
-	case asgnAppend:
-		emitAppend()
-	case asgnMaybeAppend:
-		// If we are not sure variable has been assigned before, emit setdefault
+	emitSetDefault := func() {
 		if pcv.typ == starlarkTypeList {
 			gctx.writef("%s(handle, %q)", cfnSetListDefault, pcv.name())
 		} else {
 			gctx.writef("cfg.setdefault(%q, %s)", pcv.name(), pcv.defaultValueString())
 		}
 		gctx.newLine()
+	}
+
+	switch asgn.flavor {
+	case asgnSet:
+		isSelfReferential := false
+		asgn.value.transform(func(expr starlarkExpr) starlarkExpr {
+			if ref, ok := expr.(*variableRefExpr); ok && ref.ref.name() == pcv.name() {
+				isSelfReferential = true
+			}
+			return nil
+		})
+		if isSelfReferential {
+			emitSetDefault()
+		}
+		emitAssignment()
+	case asgnAppend:
+		emitAppend()
+	case asgnMaybeAppend:
+		// If we are not sure variable has been assigned before, emit setdefault
+		emitSetDefault()
 		emitAppend()
 	case asgnMaybeSet:
 		gctx.writef("if cfg.get(%q) == None:", pcv.nam)