From df298b3bed98232773a99c8ba5b913e221525c64 Mon Sep 17 00:00:00 2001
From: Martin Stjernholm <mast@google.com>
Date: Fri, 21 May 2021 20:57:29 +0100
Subject: [PATCH] Fix indexing bug when config.Arches() returns an empty array.

This happens when com.android.art.host is not disabled in
prebuilts/build-tools/build-prebuilts.sh.

Test: m nothing
Test: env OUT_DIR=out prebuilts/build-tools/build-prebuilts.sh
  on the aosp-build-tools branch
Bug: 188922057
Change-Id: Ib21d17bb627e4cf7faee320febe65e1bb4566d4e
---
 apex/apex.go      | 26 ++++++++++++++------------
 apex/apex_test.go | 22 ++++++++++++++++++++++
 2 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/apex/apex.go b/apex/apex.go
index da4f472d1..34483272e 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -741,20 +741,22 @@ func (a *apexBundle) DepsMutator(ctx android.BottomUpMutatorContext) {
 		}
 	}
 
-	// For prebuilt_etc, use the first variant (64 on 64/32bit device, 32 on 32bit device)
-	// regardless of the TARGET_PREFER_* setting. See b/144532908
-	archForPrebuiltEtc := config.Arches()[0]
-	for _, arch := range config.Arches() {
-		// Prefer 64-bit arch if there is any
-		if arch.ArchType.Multilib == "lib64" {
-			archForPrebuiltEtc = arch
-			break
+	if prebuilts := a.properties.Prebuilts; len(prebuilts) > 0 {
+		// For prebuilt_etc, use the first variant (64 on 64/32bit device, 32 on 32bit device)
+		// regardless of the TARGET_PREFER_* setting. See b/144532908
+		archForPrebuiltEtc := config.Arches()[0]
+		for _, arch := range config.Arches() {
+			// Prefer 64-bit arch if there is any
+			if arch.ArchType.Multilib == "lib64" {
+				archForPrebuiltEtc = arch
+				break
+			}
 		}
+		ctx.AddFarVariationDependencies([]blueprint.Variation{
+			{Mutator: "os", Variation: ctx.Os().String()},
+			{Mutator: "arch", Variation: archForPrebuiltEtc.String()},
+		}, prebuiltTag, prebuilts...)
 	}
-	ctx.AddFarVariationDependencies([]blueprint.Variation{
-		{Mutator: "os", Variation: ctx.Os().String()},
-		{Mutator: "arch", Variation: archForPrebuiltEtc.String()},
-	}, prebuiltTag, a.properties.Prebuilts...)
 
 	// Common-arch dependencies come next
 	commonVariation := ctx.Config().AndroidCommonTarget.Variations()
diff --git a/apex/apex_test.go b/apex/apex_test.go
index 68182a712..364013fbe 100644
--- a/apex/apex_test.go
+++ b/apex/apex_test.go
@@ -7589,6 +7589,28 @@ func TestPrebuiltStubLibDep(t *testing.T) {
 	}
 }
 
+func TestHostApexInHostOnlyBuild(t *testing.T) {
+	testApex(t, `
+		apex {
+			name: "myapex",
+			host_supported: true,
+			key: "myapex.key",
+			updatable: false,
+			payload_type: "zip",
+		}
+		apex_key {
+			name: "myapex.key",
+			public_key: "testkey.avbpubkey",
+			private_key: "testkey.pem",
+		}
+	`,
+		android.FixtureModifyConfig(func(config android.Config) {
+			// We may not have device targets in all builds, e.g. in
+			// prebuilts/build-tools/build-prebuilts.sh
+			config.Targets[android.Android] = []android.Target{}
+		}))
+}
+
 func TestMain(m *testing.M) {
 	os.Exit(m.Run())
 }