aconfig: allow dots in package fields

Allow package fields to include dots.

Update the generated code based on the package name: if the package name
is com.android.example:

  - java: package com.android.example; ...
  - C++: namespace com::android::example { ... }
  - Rust: mod com { mod android { mod example { ... } } }

Also, update examples to use dots in the package fields.

Also, remove unnecessary #include from the auto-generated C++ code: the
header should not include itself.

Bug: 285000854
Test: atest aconfig.test
Change-Id: I8a5352e25c64c34dee0725202a1b7c9957819de8

tools/aconfig/src/codegen.rs

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-pub fn is_valid_identifier(s: &str) -> bool {
+pub fn is_valid_name_ident(s: &str) -> bool {
     // Identifiers must match [a-z][a-z0-9_]*
     let mut chars = s.chars();
     let Some(first) = chars.next() else {
@@ -26,18 +26,40 @@ pub fn is_valid_identifier(s: &str) -> bool {
     chars.all(|ch| ch.is_ascii_lowercase() || ch.is_ascii_digit() || ch == '_')
 }
 
+pub fn is_valid_package_ident(s: &str) -> bool {
+    s.split('.').all(is_valid_name_ident)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
     #[test]
-    fn test_is_valid_identifier() {
-        assert!(is_valid_identifier("foo"));
-        assert!(is_valid_identifier("foo_bar_123"));
+    fn test_is_valid_name_ident() {
+        assert!(is_valid_name_ident("foo"));
+        assert!(is_valid_name_ident("foo_bar_123"));
 
-        assert!(!is_valid_identifier(""));
-        assert!(!is_valid_identifier("123_foo"));
-        assert!(!is_valid_identifier("foo-bar"));
-        assert!(!is_valid_identifier("foo-b\u{00e5}r"));
+        assert!(!is_valid_name_ident(""));
+        assert!(!is_valid_name_ident("123_foo"));
+        assert!(!is_valid_name_ident("foo-bar"));
+        assert!(!is_valid_name_ident("foo-b\u{00e5}r"));
+    }
+
+    #[test]
+    fn test_is_valid_package_ident() {
+        assert!(is_valid_package_ident("foo"));
+        assert!(is_valid_package_ident("foo_bar_123"));
+        assert!(is_valid_package_ident("foo.bar"));
+        assert!(is_valid_package_ident("foo.bar.a123"));
+
+        assert!(!is_valid_package_ident(""));
+        assert!(!is_valid_package_ident("123_foo"));
+        assert!(!is_valid_package_ident("foo-bar"));
+        assert!(!is_valid_package_ident("foo-b\u{00e5}r"));
+        assert!(!is_valid_package_ident("foo.bar.123"));
+        assert!(!is_valid_package_ident(".foo.bar"));
+        assert!(!is_valid_package_ident("foo.bar."));
+        assert!(!is_valid_package_ident("."));
+        assert!(!is_valid_package_ident("foo..bar"));
     }
 }