From 72374fc62865152da43a02da8a1b8e6a4a7fd612 Mon Sep 17 00:00:00 2001
From: Cole Faust <colefaust@google.com>
Date: Thu, 5 May 2022 11:45:04 -0700
Subject: [PATCH] Flatten foreach calls that produce 2d lists

In make, the result of $(foreach $(x),$(y),$(foreach $(z),(w),a))
is a regular list, but in Starlark it's a list of lists. Flatten
the results of foreach expressions where each element is a list
so that they're regular lists of strings again.

Bug: 226974242
Test: go test
Change-Id: I3210d409aba0d807a5890e341ab1e0c0478f5930
---
 mk2rbc/mk2rbc.go      | 12 +++++++++++-
 mk2rbc/mk2rbc_test.go | 10 +++++++---
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/mk2rbc/mk2rbc.go b/mk2rbc/mk2rbc.go
index 1eae63f11..f36d4f741 100644
--- a/mk2rbc/mk2rbc.go
+++ b/mk2rbc/mk2rbc.go
@@ -1574,11 +1574,21 @@ func (p *foreachCallParser) parse(ctx *parseContext, node mkparser.Node, args *m
 		}
 	}
 
-	return &foreachExpr{
+	var result starlarkExpr = &foreachExpr{
 		varName: loopVarName,
 		list:    list,
 		action:  action,
 	}
+
+	if action.typ() == starlarkTypeList {
+		result = &callExpr{
+			name:       baseName + ".flatten_2d_list",
+			args:       []starlarkExpr{result},
+			returnType: starlarkTypeList,
+		}
+	}
+
+	return result
 }
 
 func transformNode(node starlarkNode, transformer func(expr starlarkExpr) starlarkExpr) {
diff --git a/mk2rbc/mk2rbc_test.go b/mk2rbc/mk2rbc_test.go
index 7f236bbc7..b812b617d 100644
--- a/mk2rbc/mk2rbc_test.go
+++ b/mk2rbc/mk2rbc_test.go
@@ -579,7 +579,7 @@ def init(g, handle):
     pass
   if rblf.expand_wildcard("foo*.mk"):
     pass
-  if rblf.expand_wildcard("foo*.mk bar*.mk") == ["foo1.mk", "foo2.mk", "barxyz.mk"]:␤
+  if rblf.expand_wildcard("foo*.mk bar*.mk") == ["foo1.mk", "foo2.mk", "barxyz.mk"]:
     pass
 `,
 	},
@@ -1363,6 +1363,8 @@ BOOT_KERNEL_MODULES_FILTER := $(foreach m,$(BOOT_KERNEL_MODULES),%/$(m))
 BOOT_KERNEL_MODULES_LIST := foo.ko
 BOOT_KERNEL_MODULES_LIST += bar.ko
 BOOT_KERNEL_MODULES_FILTER_2 := $(foreach m,$(BOOT_KERNEL_MODULES_LIST),%/$(m))
+NESTED_LISTS := $(foreach m,$(SOME_VAR),$(BOOT_KERNEL_MODULES_LIST))
+NESTED_LISTS_2 := $(foreach x,$(SOME_VAR),$(foreach y,$(x),prefix$(y)))
 
 FOREACH_WITH_IF := $(foreach module,\
   $(BOOT_KERNEL_MODULES_LIST),\
@@ -1382,6 +1384,8 @@ def init(g, handle):
   g["BOOT_KERNEL_MODULES_LIST"] = ["foo.ko"]
   g["BOOT_KERNEL_MODULES_LIST"] += ["bar.ko"]
   g["BOOT_KERNEL_MODULES_FILTER_2"] = ["%%/%s" % m for m in g["BOOT_KERNEL_MODULES_LIST"]]
+  g["NESTED_LISTS"] = rblf.flatten_2d_list([g["BOOT_KERNEL_MODULES_LIST"] for m in rblf.words(g.get("SOME_VAR", ""))])
+  g["NESTED_LISTS_2"] = rblf.flatten_2d_list([["prefix%s" % y for y in rblf.words(x)] for x in rblf.words(g.get("SOME_VAR", ""))])
   g["FOREACH_WITH_IF"] = [("" if rblf.filter(module, "foo.ko") else rblf.mkerror("product.mk", "module \"%s\" has an error!" % module)) for module in g["BOOT_KERNEL_MODULES_LIST"]]
   # Same as above, but not assigning it to a variable allows it to be converted to statements
   for module in g["BOOT_KERNEL_MODULES_LIST"]:
@@ -1574,10 +1578,10 @@ def init(g, handle):
   for x in rblf.words(g.get("MY_LIST_VAR", "")):
     _entry = {
       "foo/font.mk": ("foo/font", _font_init),
-    }.get("foo/%s.mk" % _x)
+    }.get("foo/%s.mk" % x)
     (_varmod, _varmod_init) = _entry if _entry else (None, None)
     if not _varmod_init:
-      rblf.mkerror("product.mk", "Cannot find %s" % ("foo/%s.mk" % _x))
+      rblf.mkerror("product.mk", "Cannot find %s" % ("foo/%s.mk" % x))
     _varmod_init(g, handle)
 `,
 	},