Fix "unknown binary op: string + list" errors

Convert lists to strings when adding them to a string.

Bug: 201700692
Test: go test
Change-Id: Iefb68f48191136e7115a6d6bfa0608c73d5afdac

2 files changed, 36 insertions, 3 deletions

diff --git a/mk2rbc/mk2rbc_test.go b/mk2rbc/mk2rbc_test.go
index 94c4fe6fa..b06ae88f4 100644
--- a/mk2rbc/mk2rbc_test.go
+++ b/mk2rbc/mk2rbc_test.go
@@ -1180,6 +1180,33 @@ def init(g, handle):
   g["BOOT_KERNEL_MODULES_FILTER_2"] = ["%%/%s" % m for m in g["BOOT_KERNEL_MODULES_LIST"]]
 `,
 	},
+	{
+		desc:   "List appended to string",
+		mkname: "product.mk",
+		in: `
+NATIVE_BRIDGE_PRODUCT_PACKAGES := \
+    libnative_bridge_vdso.native_bridge \
+    native_bridge_guest_app_process.native_bridge \
+    native_bridge_guest_linker.native_bridge
+
+NATIVE_BRIDGE_MODIFIED_GUEST_LIBS := \
+    libaaudio \
+    libamidi \
+    libandroid \
+    libandroid_runtime
+
+NATIVE_BRIDGE_PRODUCT_PACKAGES += \
+    $(addsuffix .native_bridge,$(NATIVE_BRIDGE_ORIG_GUEST_LIBS))
+`,
+		expected: `load("//build/make/core:product_config.rbc", "rblf")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+  g["NATIVE_BRIDGE_PRODUCT_PACKAGES"] = "libnative_bridge_vdso.native_bridge      native_bridge_guest_app_process.native_bridge      native_bridge_guest_linker.native_bridge"
+  g["NATIVE_BRIDGE_MODIFIED_GUEST_LIBS"] = "libaaudio      libamidi      libandroid      libandroid_runtime"
+  g["NATIVE_BRIDGE_PRODUCT_PACKAGES"] += " " + " ".join(rblf.addsuffix(".native_bridge", g.get("NATIVE_BRIDGE_ORIG_GUEST_LIBS", "")))
+`,
+	},
 }
 
 var known_variables = []struct {
diff --git a/mk2rbc/variable.go b/mk2rbc/variable.go
index 6b67a7cb9..f7adca568 100644
--- a/mk2rbc/variable.go
+++ b/mk2rbc/variable.go
@@ -81,10 +81,12 @@ func (pcv productConfigVariable) emitSet(gctx *generationContext, asgn *assignme
 	emitAppend := func() {
 		pcv.emitGet(gctx, true)
 		gctx.write(" += ")
+		value := asgn.value
 		if pcv.valueType() == starlarkTypeString {
 			gctx.writef(`" " + `)
+			value = &toStringExpr{expr: value}
 		}
-		asgn.value.emit(gctx)
+		value.emit(gctx)
 	}
 
 	switch asgn.flavor {
@@ -136,10 +138,12 @@ func (scv otherGlobalVariable) emitSet(gctx *generationContext, asgn *assignment
 	emitAppend := func() {
 		scv.emitGet(gctx, true)
 		gctx.write(" += ")
+		value := asgn.value
 		if scv.valueType() == starlarkTypeString {
 			gctx.writef(`" " + `)
+			value = &toStringExpr{expr: value}
 		}
-		asgn.value.emit(gctx)
+		value.emit(gctx)
 	}
 
 	switch asgn.flavor {
@@ -193,10 +197,12 @@ func (lv localVariable) emitSet(gctx *generationContext, asgn *assignmentNode) {
 	case asgnAppend:
 		lv.emitGet(gctx, false)
 		gctx.write(" += ")
+		value := asgn.value
 		if lv.valueType() == starlarkTypeString {
 			gctx.writef(`" " + `)
+			value = &toStringExpr{expr: value}
 		}
-		asgn.value.emit(gctx)
+		value.emit(gctx)
 	case asgnMaybeAppend:
 		gctx.writef("%s(%q, ", cfnLocalAppend, lv)
 		asgn.value.emit(gctx)