Fix include paths that match one file being included unconditionally

In aosp/1962181 an "optimization" was added where if an include
path with a variable only matches one file, that file would be
called directly instead of going through the whole _entry
variable.

This doesn't work when there is an inherit-product-if-exists call
that matches one file, but that file isn't the one that is specified
at runtime. In reality, the inherit-product-if-exists call should
see that the file doesn't exist and not include anything.

Fixes: 222341691
Test: go test
Change-Id: If8789de0013726137683078355161eecdec009b1
diff --git a/mk2rbc/mk2rbc.go b/mk2rbc/mk2rbc.go
index 7c1176b..74053fe 100644
--- a/mk2rbc/mk2rbc.go
+++ b/mk2rbc/mk2rbc.go
@@ -807,20 +807,16 @@
 	if len(matchingPaths) > maxMatchingFiles {
 		return []starlarkNode{ctx.newBadNode(v, "there are >%d files matching the pattern, please rewrite it", maxMatchingFiles)}
 	}
-	if len(matchingPaths) == 1 {
-		res := inheritedStaticModule{ctx.newDependentModule(matchingPaths[0], loadAlways && ctx.ifNestLevel == 0), loadAlways}
-		return []starlarkNode{processModule(res)}
-	} else {
-		needsWarning := pathPattern[0] == "" && len(ctx.includeTops) == 0
-		res := inheritedDynamicModule{*varPath, []*moduleInfo{}, loadAlways, ctx.errorLocation(v), needsWarning}
-		for _, p := range matchingPaths {
-			// A product configuration files discovered dynamically may attempt to inherit
-			// from another one which does not exist in this source tree. Prevent load errors
-			// by always loading the dynamic files as optional.
-			res.candidateModules = append(res.candidateModules, ctx.newDependentModule(p, true))
-		}
-		return []starlarkNode{processModule(res)}
+
+	needsWarning := pathPattern[0] == "" && len(ctx.includeTops) == 0
+	res := inheritedDynamicModule{*varPath, []*moduleInfo{}, loadAlways, ctx.errorLocation(v), needsWarning}
+	for _, p := range matchingPaths {
+		// A product configuration files discovered dynamically may attempt to inherit
+		// from another one which does not exist in this source tree. Prevent load errors
+		// by always loading the dynamic files as optional.
+		res.candidateModules = append(res.candidateModules, ctx.newDependentModule(p, true))
 	}
+	return []starlarkNode{processModule(res)}
 }
 
 func (ctx *parseContext) findMatchingPaths(pattern []string) []string {
diff --git a/mk2rbc/mk2rbc_test.go b/mk2rbc/mk2rbc_test.go
index a162021..55d48ff 100644
--- a/mk2rbc/mk2rbc_test.go
+++ b/mk2rbc/mk2rbc_test.go
@@ -1081,7 +1081,13 @@
 def init(g, handle):
   cfg = rblf.cfg(handle)
   g["MY_PATH"] = "foo"
-  rblf.inherit(handle, "vendor/foo1/cfg", _cfg_init)
+  _entry = {
+    "vendor/foo1/cfg.mk": ("vendor/foo1/cfg", _cfg_init),
+  }.get("%s/cfg.mk" % g["MY_PATH"])
+  (_varmod, _varmod_init) = _entry if _entry else (None, None)
+  if not _varmod_init:
+    rblf.mkerror("product.mk", "Cannot find %s" % ("%s/cfg.mk" % g["MY_PATH"]))
+  rblf.inherit(handle, _varmod, _varmod_init)
 `,
 	},
 	{
@@ -1101,8 +1107,20 @@
 def init(g, handle):
   cfg = rblf.cfg(handle)
   g["MY_PATH"] = "foo"
-  rblf.inherit(handle, "vendor/foo1/cfg", _cfg_init)
-  rblf.inherit(handle, "vendor/foo1/cfg", _cfg_init)
+  _entry = {
+    "vendor/foo1/cfg.mk": ("vendor/foo1/cfg", _cfg_init),
+  }.get("%s/cfg.mk" % g["MY_PATH"])
+  (_varmod, _varmod_init) = _entry if _entry else (None, None)
+  if not _varmod_init:
+    rblf.mkerror("product.mk", "Cannot find %s" % ("%s/cfg.mk" % g["MY_PATH"]))
+  rblf.inherit(handle, _varmod, _varmod_init)
+  _entry = {
+    "vendor/foo1/cfg.mk": ("vendor/foo1/cfg", _cfg_init),
+  }.get("%s/cfg.mk" % g["MY_PATH"])
+  (_varmod, _varmod_init) = _entry if _entry else (None, None)
+  if not _varmod_init:
+    rblf.mkerror("product.mk", "Cannot find %s" % ("%s/cfg.mk" % g["MY_PATH"]))
+  rblf.inherit(handle, _varmod, _varmod_init)
 `,
 	},
 	{
@@ -1126,9 +1144,21 @@
 
 def init(g, handle):
   cfg = rblf.cfg(handle)
-  rblf.inherit(handle, "foo/font", _font_init)
+  _entry = {
+    "foo/font.mk": ("foo/font", _font_init),
+  }.get("%s/font.mk" % g.get("MY_VAR", ""))
+  (_varmod, _varmod_init) = _entry if _entry else (None, None)
+  if not _varmod_init:
+    rblf.mkerror("product.mk", "Cannot find %s" % ("%s/font.mk" % g.get("MY_VAR", "")))
+  rblf.inherit(handle, _varmod, _varmod_init)
   # There's some space and even this comment between the include_top and the inherit-product
-  rblf.inherit(handle, "foo/font", _font_init)
+  _entry = {
+    "foo/font.mk": ("foo/font", _font_init),
+  }.get("%s/font.mk" % g.get("MY_VAR", ""))
+  (_varmod, _varmod_init) = _entry if _entry else (None, None)
+  if not _varmod_init:
+    rblf.mkerror("product.mk", "Cannot find %s" % ("%s/font.mk" % g.get("MY_VAR", "")))
+  rblf.inherit(handle, _varmod, _varmod_init)
   rblf.mkwarning("product.mk:11", "Please avoid starting an include path with a variable. See https://source.android.com/setup/build/bazel/product_config/issues/includes for details.")
   _entry = {
     "foo/font.mk": ("foo/font", _font_init),