Remove support for unused env vars from sdk snapshot generation

The following environment variables are no longer used when generating
sdk snapshots:

* SOONG_SDK_SNAPSHOT_PREFER - we can control the modules that are
  preferred at build time now.

* SOONG_SDK_SNAPSHOT_USE_SOURCE_CONFIG_VAR - this is done as a
  post-processing step by the mainline_module_sdks.sh script to avoid
  having to regenerate the ninja files for every module.

* SOONG_SDK_SNAPSHOT_VERSION - support for this was removed a long time
  ago but was still referenced from dumpvars.go.

Bug: 259095197
Test: m nothing
      # Searched for uses of these variables but could not find any
      # outside the build.
Change-Id: Id2b32b29ff6f09faffea43292f549ba13acd956d
(cherry picked from commit 82d75ade2a7dd0dbcd483c46e833ce697a443a34)
Merged-In: Id2b32b29ff6f09faffea43292f549ba13acd956d

3 files changed, 1 insertions, 110 deletions

diff --git a/sdk/sdk_test.go b/sdk/sdk_test.go
index 2f9aee9da..108a664ea 100644
--- a/sdk/sdk_test.go
+++ b/sdk/sdk_test.go
@@ -409,60 +409,6 @@ java_import {
 		)
 	})
 
-	t.Run("SOONG_SDK_SNAPSHOT_PREFER=true", func(t *testing.T) {
-		result := android.GroupFixturePreparers(
-			preparer,
-			android.FixtureMergeEnv(map[string]string{
-				"SOONG_SDK_SNAPSHOT_PREFER": "true",
-			}),
-		).RunTest(t)
-
-		checkZipFile(t, result, "out/soong/.intermediates/mysdk/common_os/mysdk-current.zip")
-
-		CheckSnapshot(t, result, "mysdk", "",
-			checkAndroidBpContents(`
-// This is auto-generated. DO NOT EDIT.
-
-java_import {
-    name: "myjavalib",
-    prefer: true,
-    visibility: ["//visibility:public"],
-    apex_available: ["//apex_available:platform"],
-    jars: ["java/myjavalib.jar"],
-}
-			`),
-		)
-	})
-
-	t.Run("SOONG_SDK_SNAPSHOT_USE_SOURCE_CONFIG_VAR=module:build_from_source", func(t *testing.T) {
-		result := android.GroupFixturePreparers(
-			preparer,
-			android.FixtureMergeEnv(map[string]string{
-				"SOONG_SDK_SNAPSHOT_USE_SOURCE_CONFIG_VAR": "module:build_from_source",
-			}),
-		).RunTest(t)
-
-		checkZipFile(t, result, "out/soong/.intermediates/mysdk/common_os/mysdk-current.zip")
-
-		CheckSnapshot(t, result, "mysdk", "",
-			checkAndroidBpContents(`
-// This is auto-generated. DO NOT EDIT.
-
-java_import {
-    name: "myjavalib",
-    prefer: false,
-    use_source_config_var: {
-        config_namespace: "module",
-        var_name: "build_from_source",
-    },
-    visibility: ["//visibility:public"],
-    apex_available: ["//apex_available:platform"],
-    jars: ["java/myjavalib.jar"],
-}
-			`),
-		)
-	})
-
 	t.Run("SOONG_SDK_SNAPSHOT_TARGET_BUILD_RELEASE=S", func(t *testing.T) {
 		result := android.GroupFixturePreparers(
 			prepareForSdkTestWithJava,
diff --git a/sdk/update.go b/sdk/update.go
index 92a13fa7f..baa203302 100644
--- a/sdk/update.go
+++ b/sdk/update.go
@@ -34,41 +34,6 @@ import (
 // Environment variables that affect the generated snapshot
 // ========================================================
 //
-// SOONG_SDK_SNAPSHOT_PREFER
-//     By default every module in the generated snapshot has prefer: false. Building it
-//     with SOONG_SDK_SNAPSHOT_PREFER=true will force them to use prefer: true.
-//
-// SOONG_SDK_SNAPSHOT_USE_SOURCE_CONFIG_VAR
-//     If set this specifies the Soong config var that can be used to control whether the prebuilt
-//     modules from the generated snapshot or the original source modules. Values must be a colon
-//     separated pair of strings, the first of which is the Soong config namespace, and the second
-//     is the name of the variable within that namespace.
-//
-//     The config namespace and var name are used to set the `use_source_config_var` property. That
-//     in turn will cause the generated prebuilts to use the soong config variable to select whether
-//     source or the prebuilt is used.
-//     e.g. If an sdk snapshot is built using:
-//       m SOONG_SDK_SNAPSHOT_USE_SOURCE_CONFIG_VAR=acme:build_from_source sdkextensions-sdk
-//     Then the resulting snapshot will include:
-//       use_source_config_var: {
-//         config_namespace: "acme",
-//         var_name: "build_from_source",
-//       }
-//
-//     Assuming that the config variable is defined in .mk using something like:
-//       $(call add_soong_config_namespace,acme)
-//       $(call add_soong_config_var_value,acme,build_from_source,true)
-//
-//     Then when the snapshot is unpacked in the repository it will have the following behavior:
-//       m droid - will use the sdkextensions-sdk prebuilts if present. Otherwise, it will use the
-//           sources.
-//       m SOONG_CONFIG_acme_build_from_source=true droid - will use the sdkextensions-sdk
-//            sources, if present. Otherwise, it will use the prebuilts.
-//
-//     This is a temporary mechanism to control the prefer flags and will be removed once a more
-//     maintainable solution has been implemented.
-//     TODO(b/174997203): Remove when no longer necessary.
-//
 // SOONG_SDK_SNAPSHOT_TARGET_BUILD_RELEASE
 //     This allows the target build release (i.e. the release version of the build within which
 //     the snapshot will be used) of the snapshot to be specified. If unspecified then it defaults
@@ -2019,29 +1984,12 @@ func (s *sdk) createMemberSnapshot(ctx *memberContext, member *sdkMember, bpModu
 
 	// Do not add the prefer property if the member snapshot module is a source module type.
 	moduleCtx := ctx.sdkMemberContext
-	config := moduleCtx.Config()
 	if !memberType.UsesSourceModuleTypeInSnapshot() {
-		// Set the prefer based on the environment variable. This is a temporary work around to allow a
-		// snapshot to be created that sets prefer: true.
-		// TODO(b/174997203): Remove once the ability to select the modules to prefer can be done
-		//  dynamically at build time not at snapshot generation time.
-		prefer := config.IsEnvTrue("SOONG_SDK_SNAPSHOT_PREFER")
-
 		// Set prefer. Setting this to false is not strictly required as that is the default but it does
 		// provide a convenient hook to post-process the generated Android.bp file, e.g. in tests to
 		// check the behavior when a prebuilt is preferred. It also makes it explicit what the default
 		// behavior is for the module.
-		bpModule.insertAfter("name", "prefer", prefer)
-
-		configVar := config.Getenv("SOONG_SDK_SNAPSHOT_USE_SOURCE_CONFIG_VAR")
-		if configVar != "" {
-			parts := strings.Split(configVar, ":")
-			cfp := android.ConfigVarProperties{
-				Config_namespace: proptools.StringPtr(parts[0]),
-				Var_name:         proptools.StringPtr(parts[1]),
-			}
-			bpModule.insertAfter("prefer", "use_source_config_var", cfp)
-		}
+		bpModule.insertAfter("name", "prefer", false)
 	}
 
 	variants := selectApexVariantsWhereAvailable(ctx, member.variants)
diff --git a/ui/build/dumpvars.go b/ui/build/dumpvars.go
index 285f1569b..45bfe5dfa 100644
--- a/ui/build/dumpvars.go
+++ b/ui/build/dumpvars.go
@@ -162,10 +162,7 @@ var BannerVars = []string{
 	"OUT_DIR",
 	"AUX_OS_VARIANT_LIST",
 	"PRODUCT_SOONG_NAMESPACES",
-	"SOONG_SDK_SNAPSHOT_PREFER",
 	"SOONG_SDK_SNAPSHOT_TARGET_BUILD_RELEASE",
-	"SOONG_SDK_SNAPSHOT_USE_SOURCE_CONFIG_VAR",
-	"SOONG_SDK_SNAPSHOT_VERSION",
 }
 
 func Banner(make_vars map[string]string) string {