Add flag for enabling only new storage and use in aflags

Change-Id: I73218de38d005d77987d5103364a102cec3abc07
Test: m && cargo t
Bug: 324436145

tools/aconfig/aconfig_flags/Android.bp

@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+rust_library {
+    name: "libaconfig_flags",
+    crate_name: "aconfig_flags",
+    srcs: [
+        "src/lib.rs",
+    ],
+    rustlibs: [
+        "libaconfig_flags_rust",
+    ],
+    host_supported: true,
+}
+
+aconfig_declarations {
+    name: "aconfig_flags",
+    package: "com.android.aconfig.flags",
+    container: "system",
+    srcs: ["flags.aconfig"],
+}
+
+rust_aconfig_library {
+    name: "libaconfig_flags_rust",
+    crate_name: "aconfig_flags_rust",
+    aconfig_declarations: "aconfig_flags",
+    host_supported: true,
+}
+
+cc_aconfig_library {
+    name: "libaconfig_flags_cc",
+    aconfig_declarations: "aconfig_flags",
+}

tools/aconfig/aconfig_flags/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "aconfig_flags"
+version = "0.1.0"
+edition = "2021"
+
+[features]
+default = ["cargo"]
+cargo = []
+
+[dependencies]

tools/aconfig/aconfig_flags/flags.aconfig

@@ -0,0 +1,9 @@
+package: "com.android.aconfig.flags"
+container: "system"
+
+flag {
+  name: "enable_only_new_storage"
+  namespace: "core_experiments_team_internal"
+  bug: "312235596"
+  description: "When enabled, aconfig flags are read from the new aconfig storage only."
+}

tools/aconfig/aconfig_flags/src/lib.rs

@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//! `aconfig_flags` is a crate for reading aconfig flags from Rust
+// When building with the Android tool-chain
+//
+//   - the flag functions will read from aconfig_flags_inner
+//   - the feature "cargo" will be disabled
+//
+// When building with cargo
+//
+//   - the flag functions will all return some trivial value, like true
+//   - the feature "cargo" will be enabled
+//
+// This module hides these differences from the rest of aconfig.
+
+/// Module used when building with the Android tool-chain
+#[cfg(not(feature = "cargo"))]
+pub mod auto_generated {
+    /// Returns the value for the enable_only_new_storage flag.
+    pub fn enable_only_new_storage() -> bool {
+        aconfig_flags_rust::enable_only_new_storage()
+    }
+}
+
+/// Module used when building with cargo
+#[cfg(feature = "cargo")]
+pub mod auto_generated {
+    /// Returns a placeholder value for the enable_only_new_storage flag.
+    pub fn enable_only_new_storage() -> bool {
+        // Used only to enable typechecking and testing with cargo
+        true
+    }
+}

tools/aconfig/aflags/Android.bp

@@ -10,6 +10,7 @@ rust_defaults {
     srcs: ["src/main.rs"],
     rustlibs: [
         "libaconfig_device_paths",
+        "libaconfig_flags",
         "libaconfig_protos",
         "libaconfigd_protos",
         "libaconfig_storage_read_api",
@@ -24,6 +25,7 @@ rust_defaults {
 
 rust_binary {
     name: "aflags",
+    host_supported: true,
     defaults: ["aflags.defaults"],
 }
 

tools/aconfig/aflags/Cargo.toml

@@ -15,3 +15,4 @@ aconfig_storage_file = { version = "0.1.0", path = "../aconfig_storage_file" }
 aconfig_storage_read_api = { version = "0.1.0", path = "../aconfig_storage_read_api" }
 clap = {version = "4.5.2" }
 aconfig_device_paths = { version = "0.1.0", path = "../aconfig_device_paths" }
+aconfig_flags = { version = "0.1.0", path = "../aconfig_flags" }

tools/aconfig/aflags/src/main.rs

@@ -164,10 +164,6 @@ struct Cli {
 enum Command {
     /// List all aconfig flags on this device.
     List {
-        /// Read from the new flag storage.
-        #[clap(long)]
-        use_new_storage: bool,
-
         /// Optionally filter by container name.
         #[clap(short = 'c', long = "container")]
         container: Option<String>,
@@ -184,6 +180,9 @@ enum Command {
         /// <package>.<flag_name>
         qualified_name: String,
     },
+
+    /// Display which flag storage backs aconfig flags.
+    WhichBacking,
 }
 
 struct PaddingInfo {
@@ -282,21 +281,31 @@ fn list(source_type: FlagSourceType, container: Option<String>) -> Result<String
     Ok(result)
 }
 
+fn display_which_backing() -> String {
+    if aconfig_flags::auto_generated::enable_only_new_storage() {
+        "aconfig_storage".to_string()
+    } else {
+        "device_config".to_string()
+    }
+}
+
 fn main() -> Result<()> {
     ensure!(nix::unistd::Uid::current().is_root(), "must be root");
 
     let cli = Cli::parse();
     let output = match cli.command {
-        Command::List { use_new_storage: true, container } => {
+        Command::List { container } => {
-            list(FlagSourceType::AconfigStorage, container)
+            if aconfig_flags::auto_generated::enable_only_new_storage() {
-                .map_err(|err| anyhow!("storage may not be enabled: {err}"))
+                list(FlagSourceType::AconfigStorage, container)
-                .map(Some)
+                    .map_err(|err| anyhow!("storage may not be enabled: {err}"))
-        }
+                    .map(Some)
-        Command::List { use_new_storage: false, container } => {
+            } else {
-            list(FlagSourceType::DeviceConfig, container).map(Some)
+                list(FlagSourceType::DeviceConfig, container).map(Some)
+            }
         }
         Command::Enable { qualified_name } => set_flag(&qualified_name, "true").map(|_| None),
         Command::Disable { qualified_name } => set_flag(&qualified_name, "false").map(|_| None),
+        Command::WhichBacking => Ok(Some(display_which_backing())),
     };
     match output {
         Ok(Some(text)) => println!("{text}"),