aconfig: add namespace field to flag_declaration and parsed_flag

Add a new field to the proto messages flag_declaration and parsed_flag.

The new field will be used verbatim as a parameter when calling
DeviceConfig.getBoolean to read the value of a READ_WRITE flag. See the
DeviceConfig API for more info.

Note: not to be confused with the old namespace field, which has been
renamed to package.

Bug: 285211724
Test: atest aconfig.test
Change-Id: I2181be7b5e98fc334e5277fb5f7e386f1fe0b550

tools/aconfig/src/codegen.rs

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+use anyhow::{ensure, Result};
+
 pub fn is_valid_name_ident(s: &str) -> bool {
     // Identifiers must match [a-z][a-z0-9_]*
     let mut chars = s.chars();
@@ -30,6 +32,12 @@ pub fn is_valid_package_ident(s: &str) -> bool {
     s.split('.').all(is_valid_name_ident)
 }
 
+pub fn create_device_config_ident(package: &str, flag_name: &str) -> Result<String> {
+    ensure!(is_valid_package_ident(package), "bad package");
+    ensure!(is_valid_package_ident(flag_name), "bad flag name");
+    Ok(format!("{}.{}", package, flag_name))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -62,4 +70,12 @@ mod tests {
         assert!(!is_valid_package_ident("."));
         assert!(!is_valid_package_ident("foo..bar"));
     }
+
+    #[test]
+    fn test_create_device_config_ident() {
+        assert_eq!(
+            "com.foo.bar.some_flag",
+            create_device_config_ident("com.foo.bar", "some_flag").unwrap()
+        );
+    }
 }