Fix package boundary in glob expansion with checked in BUILD files.

For directories without an Android.bp file, if they contain a merged
checked in BUILD file, it becomes a package boundary in the symlink
forest. However, the current glob expansion is only aware of Android.bp
files, but not merged BUILD files, so it generates glob expansions
incorrectly for files that cross the package boundary.

This CL fixes that by making the package boundary function aware of the
keepExistingBuildFile allowlist. See the new test cases for example.

Also stop using the same global bp2buildConfig for every test case to
allow each test to define their own bp2build allowlists.

Bug: 185358476
Test: new unit tests

Change-Id: Ifcd1283480a09a642ef4343e5bbc599583524577

bp2build/testing.go

@@ -30,13 +30,6 @@ import (
 )
 
 var (
-	// A default configuration for tests to not have to specify bp2build_available on top level targets.
-	bp2buildConfig = android.NewBp2BuildAllowlist().SetDefaultConfig(
-		allowlists.Bp2BuildConfig{
-			android.Bp2BuildTopLevel: allowlists.Bp2BuildDefaultTrueRecursively,
-		},
-	)
-
 	buildDir string
 )
 
@@ -87,6 +80,11 @@ type Bp2buildTestCase struct {
 	// An error with a string contained within the string of the expected error
 	ExpectedErr         error
 	UnconvertedDepsMode unconvertedDepsMode
+
+	// For every directory listed here, the BUILD file for that directory will
+	// be merged with the generated BUILD file. This allows custom BUILD targets
+	// to be used in tests, or use BUILD files to draw package boundaries.
+	KeepBuildFileForDirs []string
 }
 
 func RunBp2BuildTestCase(t *testing.T, registerModuleTypes func(ctx android.RegistrationContext), tc Bp2buildTestCase) {
@@ -107,6 +105,18 @@ func RunBp2BuildTestCase(t *testing.T, registerModuleTypes func(ctx android.Regi
 
 	registerModuleTypes(ctx)
 	ctx.RegisterModuleType(tc.ModuleTypeUnderTest, tc.ModuleTypeUnderTestFactory)
+
+	// A default configuration for tests to not have to specify bp2build_available on top level targets.
+	bp2buildConfig := android.NewBp2BuildAllowlist().SetDefaultConfig(
+		allowlists.Bp2BuildConfig{
+			android.Bp2BuildTopLevel: allowlists.Bp2BuildDefaultTrueRecursively,
+		},
+	)
+	for _, f := range tc.KeepBuildFileForDirs {
+		bp2buildConfig.SetKeepExistingBuildFile(map[string]bool{
+			f: /*recursive=*/ false,
+		})
+	}
 	ctx.RegisterBp2BuildConfig(bp2buildConfig)
 	ctx.RegisterForBazelConversion()