aconfig: sort items in cache by name

Introduce a builder pattern for constructing a cache from flag
declarations and flag values. Teach the builder to sort the flags by
name as the last step. This will ensure consistent dump output
regardless of the order flags are specified in the input files.

Bug: 279485059
Test: atest aconfig.test
Change-Id: Icdd62f51fa3761a469663f17581a83d9909e9ffe

tools/aconfig/src/cache.rs

@@ -51,72 +51,42 @@ pub struct Cache {
     items: Vec<Item>,
 }
 
-impl Cache {
+// TODO: replace this function with Iterator.is_sorted_by_key(...)) when that API becomes stable
-    pub fn new(namespace: String) -> Result<Cache> {
+fn iter_is_sorted_by_key<'a, T: 'a, F, K>(iter: impl Iterator<Item = &'a T>, f: F) -> bool
-        ensure!(!namespace.is_empty(), "empty namespace");
+where
-        Ok(Cache { namespace, items: vec![] })
+    F: FnMut(&'a T) -> K,
+    K: PartialOrd<K>,
+{
+    let mut last: Option<K> = None;
+    for current in iter.map(f) {
+        if let Some(l) = last {
+            if l > current {
+                return false;
+            }
+        }
+        last = Some(current);
     }
+    true
+}
 
+impl Cache {
     pub fn read_from_reader(reader: impl Read) -> Result<Cache> {
-        serde_json::from_reader(reader).map_err(|e| e.into())
+        let cache: Cache = serde_json::from_reader(reader)?;
+        ensure!(
+            iter_is_sorted_by_key(cache.iter(), |item| &item.name),
+            "internal error: flags in cache file not sorted"
+        );
+        Ok(cache)
     }
 
     pub fn write_to_writer(&self, writer: impl Write) -> Result<()> {
+        ensure!(
+            iter_is_sorted_by_key(self.iter(), |item| &item.name),
+            "internal error: flags in cache file not sorted"
+        );
         serde_json::to_writer(writer, self).map_err(|e| e.into())
     }
 
-    pub fn add_flag_declaration(
-        &mut self,
-        source: Source,
-        declaration: FlagDeclaration,
-    ) -> Result<()> {
-        ensure!(!declaration.name.is_empty(), "empty flag name");
-        ensure!(!declaration.description.is_empty(), "empty flag description");
-        ensure!(
-            self.items.iter().all(|item| item.name != declaration.name),
-            "failed to declare flag {} from {}: flag already declared",
-            declaration.name,
-            source
-        );
-        self.items.push(Item {
-            namespace: self.namespace.clone(),
-            name: declaration.name.clone(),
-            description: declaration.description,
-            state: DEFAULT_FLAG_STATE,
-            permission: DEFAULT_FLAG_PERMISSION,
-            trace: vec![Tracepoint {
-                source,
-                state: DEFAULT_FLAG_STATE,
-                permission: DEFAULT_FLAG_PERMISSION,
-            }],
-        });
-        Ok(())
-    }
-
-    pub fn add_flag_value(&mut self, source: Source, value: FlagValue) -> Result<()> {
-        ensure!(!value.namespace.is_empty(), "empty flag namespace");
-        ensure!(!value.name.is_empty(), "empty flag name");
-        ensure!(
-            value.namespace == self.namespace,
-            "failed to set values for flag {}/{} from {}: expected namespace {}",
-            value.namespace,
-            value.name,
-            source,
-            self.namespace
-        );
-        let Some(existing_item) = self.items.iter_mut().find(|item| item.name == value.name) else {
-            bail!("failed to set values for flag {}/{} from {}: flag not declared", value.namespace, value.name, source);
-        };
-        existing_item.state = value.state;
-        existing_item.permission = value.permission;
-        existing_item.trace.push(Tracepoint {
-            source,
-            state: value.state,
-            permission: value.permission,
-        });
-        Ok(())
-    }
-
     pub fn iter(&self) -> impl Iterator<Item = &Item> {
         self.items.iter()
     }
@@ -131,6 +101,80 @@ impl Cache {
     }
 }
 
+#[derive(Debug)]
+pub struct CacheBuilder {
+    cache: Cache,
+}
+
+impl CacheBuilder {
+    pub fn new(namespace: String) -> Result<CacheBuilder> {
+        ensure!(!namespace.is_empty(), "empty namespace");
+        let cache = Cache { namespace, items: vec![] };
+        Ok(CacheBuilder { cache })
+    }
+
+    pub fn add_flag_declaration(
+        &mut self,
+        source: Source,
+        declaration: FlagDeclaration,
+    ) -> Result<&mut CacheBuilder> {
+        ensure!(!declaration.name.is_empty(), "empty flag name");
+        ensure!(!declaration.description.is_empty(), "empty flag description");
+        ensure!(
+            self.cache.items.iter().all(|item| item.name != declaration.name),
+            "failed to declare flag {} from {}: flag already declared",
+            declaration.name,
+            source
+        );
+        self.cache.items.push(Item {
+            namespace: self.cache.namespace.clone(),
+            name: declaration.name.clone(),
+            description: declaration.description,
+            state: DEFAULT_FLAG_STATE,
+            permission: DEFAULT_FLAG_PERMISSION,
+            trace: vec![Tracepoint {
+                source,
+                state: DEFAULT_FLAG_STATE,
+                permission: DEFAULT_FLAG_PERMISSION,
+            }],
+        });
+        Ok(self)
+    }
+
+    pub fn add_flag_value(
+        &mut self,
+        source: Source,
+        value: FlagValue,
+    ) -> Result<&mut CacheBuilder> {
+        ensure!(!value.namespace.is_empty(), "empty flag namespace");
+        ensure!(!value.name.is_empty(), "empty flag name");
+        ensure!(
+            value.namespace == self.cache.namespace,
+            "failed to set values for flag {}/{} from {}: expected namespace {}",
+            value.namespace,
+            value.name,
+            source,
+            self.cache.namespace
+        );
+        let Some(existing_item) = self.cache.items.iter_mut().find(|item| item.name == value.name) else {
+            bail!("failed to set values for flag {}/{} from {}: flag not declared", value.namespace, value.name, source);
+        };
+        existing_item.state = value.state;
+        existing_item.permission = value.permission;
+        existing_item.trace.push(Tracepoint {
+            source,
+            state: value.state,
+            permission: value.permission,
+        });
+        Ok(self)
+    }
+
+    pub fn build(mut self) -> Cache {
+        self.cache.items.sort_by_cached_key(|item| item.name.clone());
+        self.cache
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -138,14 +182,14 @@ mod tests {
 
     #[test]
     fn test_add_flag_declaration() {
-        let mut cache = Cache::new("ns".to_string()).unwrap();
+        let mut builder = CacheBuilder::new("ns".to_string()).unwrap();
-        cache
+        builder
             .add_flag_declaration(
                 Source::File("first.txt".to_string()),
                 FlagDeclaration { name: "foo".to_string(), description: "desc".to_string() },
             )
             .unwrap();
-        let error = cache
+        let error = builder
             .add_flag_declaration(
                 Source::File("second.txt".to_string()),
                 FlagDeclaration { name: "foo".to_string(), description: "desc".to_string() },
@@ -155,17 +199,26 @@ mod tests {
             &format!("{:?}", error),
             "failed to declare flag foo from second.txt: flag already declared"
         );
+        builder
+            .add_flag_declaration(
+                Source::File("first.txt".to_string()),
+                FlagDeclaration { name: "bar".to_string(), description: "desc".to_string() },
+            )
+            .unwrap();
+
+        let cache = builder.build();
+
+        // check flags are sorted by name
+        assert_eq!(
+            cache.into_iter().map(|item| item.name).collect::<Vec<_>>(),
+            vec!["bar".to_string(), "foo".to_string()]
+        );
     }
 
     #[test]
     fn test_add_flag_value() {
-        fn check(cache: &Cache, name: &str, expected: (FlagState, Permission)) -> bool {
+        let mut builder = CacheBuilder::new("ns".to_string()).unwrap();
-            let item = cache.iter().find(|&item| item.name == name).unwrap();
+        let error = builder
-            item.state == expected.0 && item.permission == expected.1
-        }
-
-        let mut cache = Cache::new("ns".to_string()).unwrap();
-        let error = cache
             .add_flag_value(
                 Source::Memory,
                 FlagValue {
@@ -181,15 +234,14 @@ mod tests {
             "failed to set values for flag ns/foo from <memory>: flag not declared"
         );
 
-        cache
+        builder
             .add_flag_declaration(
                 Source::File("first.txt".to_string()),
                 FlagDeclaration { name: "foo".to_string(), description: "desc".to_string() },
             )
             .unwrap();
-        assert!(check(&cache, "foo", (DEFAULT_FLAG_STATE, DEFAULT_FLAG_PERMISSION)));
 
-        cache
+        builder
             .add_flag_value(
                 Source::Memory,
                 FlagValue {
@@ -200,9 +252,8 @@ mod tests {
                 },
             )
             .unwrap();
-        assert!(check(&cache, "foo", (FlagState::Disabled, Permission::ReadOnly)));
 
-        cache
+        builder
             .add_flag_value(
                 Source::Memory,
                 FlagValue {
@@ -213,10 +264,9 @@ mod tests {
                 },
             )
             .unwrap();
-        assert!(check(&cache, "foo", (FlagState::Enabled, Permission::ReadWrite)));
 
         // different namespace -> no-op
-        let error = cache
+        let error = builder
             .add_flag_value(
                 Source::Memory,
                 FlagValue {
@@ -228,19 +278,23 @@ mod tests {
             )
             .unwrap_err();
         assert_eq!(&format!("{:?}", error), "failed to set values for flag some-other-namespace/foo from <memory>: expected namespace ns");
-        assert!(check(&cache, "foo", (FlagState::Enabled, Permission::ReadWrite)));
+
+        let cache = builder.build();
+        let item = cache.iter().find(|&item| item.name == "foo").unwrap();
+        assert_eq!(FlagState::Enabled, item.state);
+        assert_eq!(Permission::ReadWrite, item.permission);
     }
 
     #[test]
     fn test_reject_empty_cache_namespace() {
-        Cache::new("".to_string()).unwrap_err();
+        CacheBuilder::new("".to_string()).unwrap_err();
     }
 
     #[test]
     fn test_reject_empty_flag_declaration_fields() {
-        let mut cache = Cache::new("ns".to_string()).unwrap();
+        let mut builder = CacheBuilder::new("ns".to_string()).unwrap();
 
-        let error = cache
+        let error = builder
             .add_flag_declaration(
                 Source::Memory,
                 FlagDeclaration { name: "".to_string(), description: "Description".to_string() },
@@ -248,7 +302,7 @@ mod tests {
             .unwrap_err();
         assert_eq!(&format!("{:?}", error), "empty flag name");
 
-        let error = cache
+        let error = builder
             .add_flag_declaration(
                 Source::Memory,
                 FlagDeclaration { name: "foo".to_string(), description: "".to_string() },
@@ -259,15 +313,15 @@ mod tests {
 
     #[test]
     fn test_reject_empty_flag_value_files() {
-        let mut cache = Cache::new("ns".to_string()).unwrap();
+        let mut builder = CacheBuilder::new("ns".to_string()).unwrap();
-        cache
+        builder
             .add_flag_declaration(
                 Source::Memory,
                 FlagDeclaration { name: "foo".to_string(), description: "desc".to_string() },
             )
             .unwrap();
 
-        let error = cache
+        let error = builder
             .add_flag_value(
                 Source::Memory,
                 FlagValue {
@@ -280,7 +334,7 @@ mod tests {
             .unwrap_err();
         assert_eq!(&format!("{:?}", error), "empty flag namespace");
 
-        let error = cache
+        let error = builder
             .add_flag_value(
                 Source::Memory,
                 FlagValue {
@@ -293,4 +347,11 @@ mod tests {
             .unwrap_err();
         assert_eq!(&format!("{:?}", error), "empty flag name");
     }
+
+    #[test]
+    fn test_iter_is_sorted_by_key() {
+        assert!(iter_is_sorted_by_key(["a", "b", "c"].iter(), |s| s));
+        assert!(iter_is_sorted_by_key(Vec::<&str>::new().iter(), |s| s));
+        assert!(!iter_is_sorted_by_key(["a", "c", "b"].iter(), |s| s));
+    }
 }

tools/aconfig/src/codegen_cpp.rs

@@ -64,13 +64,14 @@ fn create_class_element(item: &Item) -> ClassElement {
 mod tests {
     use super::*;
     use crate::aconfig::{FlagDeclaration, FlagState, FlagValue, Permission};
+    use crate::cache::CacheBuilder;
     use crate::commands::Source;
 
     #[test]
     fn test_cpp_codegen_build_time_flag_only() {
         let namespace = "my_namespace";
-        let mut cache = Cache::new(namespace.to_string()).unwrap();
+        let mut builder = CacheBuilder::new(namespace.to_string()).unwrap();
-        cache
+        builder
             .add_flag_declaration(
                 Source::File("aconfig_one.txt".to_string()),
                 FlagDeclaration {
@@ -78,8 +79,7 @@ mod tests {
                     description: "buildtime disable".to_string(),
                 },
             )
-            .unwrap();
+            .unwrap()
-        cache
             .add_flag_value(
                 Source::Memory,
                 FlagValue {
@@ -89,8 +89,7 @@ mod tests {
                     permission: Permission::ReadOnly,
                 },
             )
-            .unwrap();
+            .unwrap()
-        cache
             .add_flag_declaration(
                 Source::File("aconfig_two.txt".to_string()),
                 FlagDeclaration {
@@ -98,8 +97,7 @@ mod tests {
                     description: "buildtime enable".to_string(),
                 },
             )
-            .unwrap();
+            .unwrap()
-        cache
             .add_flag_value(
                 Source::Memory,
                 FlagValue {
@@ -110,6 +108,7 @@ mod tests {
                 },
             )
             .unwrap();
+        let cache = builder.build();
         let expect_content = r#"#ifndef my_namespace_HEADER_H
         #define my_namespace_HEADER_H
         #include "my_namespace.h"
@@ -144,8 +143,8 @@ mod tests {
     #[test]
     fn test_cpp_codegen_runtime_flag() {
         let namespace = "my_namespace";
-        let mut cache = Cache::new(namespace.to_string()).unwrap();
+        let mut builder = CacheBuilder::new(namespace.to_string()).unwrap();
-        cache
+        builder
             .add_flag_declaration(
                 Source::File("aconfig_one.txt".to_string()),
                 FlagDeclaration {
@@ -153,8 +152,7 @@ mod tests {
                     description: "buildtime disable".to_string(),
                 },
             )
-            .unwrap();
+            .unwrap()
-        cache
             .add_flag_declaration(
                 Source::File("aconfig_two.txt".to_string()),
                 FlagDeclaration {
@@ -162,8 +160,7 @@ mod tests {
                     description: "runtime enable".to_string(),
                 },
             )
-            .unwrap();
+            .unwrap()
-        cache
             .add_flag_value(
                 Source::Memory,
                 FlagValue {
@@ -174,6 +171,7 @@ mod tests {
                 },
             )
             .unwrap();
+        let cache = builder.build();
         let expect_content = r#"#ifndef my_namespace_HEADER_H
         #define my_namespace_HEADER_H
         #include "my_namespace.h"

tools/aconfig/src/codegen_java.rs

@@ -71,13 +71,14 @@ fn create_class_element(item: &Item) -> ClassElement {
 mod tests {
     use super::*;
     use crate::aconfig::{FlagDeclaration, FlagValue};
+    use crate::cache::CacheBuilder;
     use crate::commands::Source;
 
     #[test]
     fn test_generate_java_code() {
         let namespace = "com.example";
-        let mut cache = Cache::new(namespace.to_string()).unwrap();
+        let mut builder = CacheBuilder::new(namespace.to_string()).unwrap();
-        cache
+        builder
             .add_flag_declaration(
                 Source::File("test.txt".to_string()),
                 FlagDeclaration {
@@ -85,8 +86,7 @@ mod tests {
                     description: "buildtime enable".to_string(),
                 },
             )
-            .unwrap();
+            .unwrap()
-        cache
             .add_flag_declaration(
                 Source::File("test2.txt".to_string()),
                 FlagDeclaration {
@@ -94,8 +94,7 @@ mod tests {
                     description: "runtime disable".to_string(),
                 },
             )
-            .unwrap();
+            .unwrap()
-        cache
             .add_flag_value(
                 Source::Memory,
                 FlagValue {
@@ -106,6 +105,7 @@ mod tests {
                 },
             )
             .unwrap();
+        let cache = builder.build();
         let expect_content = r#"package com.example;
 
         import android.provider.DeviceConfig;

tools/aconfig/src/commands.rs

@@ -23,7 +23,7 @@ use std::io::Read;
 use std::path::PathBuf;
 
 use crate::aconfig::{FlagDeclarations, FlagValue};
-use crate::cache::Cache;
+use crate::cache::{Cache, CacheBuilder};
 use crate::codegen_cpp::generate_cpp_code;
 use crate::codegen_java::generate_java_code;
 use crate::protos::ProtoParsedFlags;
@@ -59,7 +59,7 @@ pub fn create_cache(
     declarations: Vec<Input>,
     values: Vec<Input>,
 ) -> Result<Cache> {
-    let mut cache = Cache::new(namespace.to_owned())?;
+    let mut builder = CacheBuilder::new(namespace.to_owned())?;
 
     for mut input in declarations {
         let mut contents = String::new();
@@ -74,7 +74,7 @@ pub fn create_cache(
             dec_list.namespace
         );
         for d in dec_list.flags.into_iter() {
-            cache.add_flag_declaration(input.source.clone(), d)?;
+            builder.add_flag_declaration(input.source.clone(), d)?;
         }
     }
 
@@ -85,11 +85,11 @@ pub fn create_cache(
             .with_context(|| format!("Failed to parse {}", input.source))?;
         for v in values_list {
             // TODO: warn about flag values that do not take effect?
-            let _ = cache.add_flag_value(input.source.clone(), v);
+            let _ = builder.add_flag_value(input.source.clone(), v);
         }
     }
 
-    Ok(cache)
+    Ok(builder.build())
 }
 
 pub fn create_java_lib(cache: &Cache) -> Result<OutputFile> {