cpp codegen redesign, unit test support

cpp codegen iteration 2, based on discussions with three internal teams
that use c++. Refer to the design doc "aconfig c++ codegen" for detailed
design. At a high level, we generate two sets of code artifacts with the
same signatured api: one for production that without any local flag
override capability, one for unit test that allows local flag overrides.
It supports static methods style interface as well as injection pattern.

Refer to the test points in the codegen_cpp.rs for examples of generated
code.

for production target codegen: aconfig create-cpp-lib --cache <cache> --out <out dir>
for test target codegen: aconfig create-cpp-lib --cache <cache> --out
<out dir> --mode test

Bug: b/279483801
Test: atest aconfig.test
Change-Id: I92fefb9623d5435525339a74f57bbd36d0afef08

tools/aconfig/src/codegen_cpp.rs

@@ -16,13 +16,18 @@
 
 use anyhow::{ensure, Result};
 use serde::Serialize;
+use std::path::PathBuf;
 use tinytemplate::TinyTemplate;
 
 use crate::codegen;
-use crate::commands::OutputFile;
+use crate::commands::{CodegenMode, OutputFile};
 use crate::protos::{ProtoFlagPermission, ProtoFlagState, ProtoParsedFlag};
 
-pub fn generate_cpp_code<'a, I>(package: &str, parsed_flags_iter: I) -> Result<OutputFile>
+pub fn generate_cpp_code<'a, I>(
+    package: &str,
+    parsed_flags_iter: I,
+    codegen_mode: CodegenMode,
+) -> Result<Vec<OutputFile>>
 where
     I: Iterator<Item = &'a ProtoParsedFlag>,
 {
@@ -37,29 +42,66 @@ where
         cpp_namespace,
         package: package.to_string(),
         readwrite,
+        for_prod: codegen_mode == CodegenMode::Production,
         class_elements,
     };
+
+    let files = [
+        FileSpec {
+            name: &format!("{}.h", header),
+            template: include_str!("../templates/cpp_exported_header.template"),
+            dir: "include",
+        },
+        FileSpec {
+            name: &format!("{}.cc", header),
+            template: include_str!("../templates/cpp_source_file.template"),
+            dir: "",
+        },
+        FileSpec {
+            name: &format!("{}_flag_provider.h", header),
+            template: match codegen_mode {
+                CodegenMode::Production => {
+                    include_str!("../templates/cpp_prod_flag_provider.template")
+                }
+                CodegenMode::Test => include_str!("../templates/cpp_test_flag_provider.template"),
+            },
+            dir: "",
+        },
+    ];
+    files.iter().map(|file| generate_file(file, &context)).collect()
+}
+
+pub fn generate_file(file: &FileSpec, context: &Context) -> Result<OutputFile> {
     let mut template = TinyTemplate::new();
-    template.add_template("cpp_code_gen", include_str!("../templates/cpp.template"))?;
+    template.add_template(file.name, file.template)?;
-    let contents = template.render("cpp_code_gen", &context)?;
+    let contents = template.render(file.name, &context)?;
-    let path = ["aconfig", &(header + ".h")].iter().collect();
+    let path: PathBuf = [&file.dir, &file.name].iter().collect();
     Ok(OutputFile { contents: contents.into(), path })
 }
 
 #[derive(Serialize)]
-struct Context {
+pub struct FileSpec<'a> {
+    pub name: &'a str,
+    pub template: &'a str,
+    pub dir: &'a str,
+}
+
+#[derive(Serialize)]
+pub struct Context {
     pub header: String,
     pub cpp_namespace: String,
     pub package: String,
     pub readwrite: bool,
+    pub for_prod: bool,
     pub class_elements: Vec<ClassElement>,
 }
 
 #[derive(Serialize)]
-struct ClassElement {
+pub struct ClassElement {
     pub readwrite: bool,
     pub default_value: String,
     pub flag_name: String,
+    pub uppercase_flag_name: String,
     pub device_config_namespace: String,
     pub device_config_flag: String,
 }
@@ -73,6 +115,7 @@ fn create_class_element(package: &str, pf: &ProtoParsedFlag) -> ClassElement {
             "false".to_string()
         },
         flag_name: pf.name().to_string(),
+        uppercase_flag_name: pf.name().to_string().to_ascii_uppercase(),
         device_config_namespace: pf.namespace().to_string(),
         device_config_flag: codegen::create_device_config_ident(package, pf.name())
             .expect("values checked at flag parse time"),
@@ -82,51 +125,325 @@ fn create_class_element(package: &str, pf: &ProtoParsedFlag) -> ClassElement {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::collections::HashMap;
 
-    #[test]
+    const EXPORTED_PROD_HEADER_EXPECTED: &str = r#"
-    fn test_generate_cpp_code() {
-        let parsed_flags = crate::test::parse_test_flags();
-        let generated =
-            generate_cpp_code(crate::test::TEST_PACKAGE, parsed_flags.parsed_flag.iter()).unwrap();
-        assert_eq!("aconfig/com_android_aconfig_test.h", format!("{}", generated.path.display()));
-        let expected = r#"
 #ifndef com_android_aconfig_test_HEADER_H
 #define com_android_aconfig_test_HEADER_H
-#include <server_configurable_flags/get_flags.h>
 
+#include <string>
+#include <memory>
+#include <server_configurable_flags/get_flags.h>
 using namespace server_configurable_flags;
 
 namespace com::android::aconfig::test {
-    static const bool disabled_ro() {
+class flag_provider_interface {
+public:
+
+    virtual ~flag_provider_interface() = default;
+
+    virtual bool disabled_ro() = 0;
+
+    virtual bool disabled_rw() = 0;
+
+    virtual bool enabled_ro() = 0;
+
+    virtual bool enabled_rw() = 0;
+
+    virtual void override_flag(std::string const&, bool) {}
+
+    virtual void reset_overrides() {}
+};
+
+extern std::unique_ptr<flag_provider_interface> provider_;
+
+extern std::string const DISABLED_RO;
+extern std::string const DISABLED_RW;
+extern std::string const ENABLED_RO;
+extern std::string const ENABLED_RW;
+
+inline bool disabled_ro() {
+    return false;
+}
+
+inline bool disabled_rw() {
+    return provider_->disabled_rw();
+}
+
+inline bool enabled_ro() {
+    return true;
+}
+
+inline bool enabled_rw() {
+    return provider_->enabled_rw();
+}
+
+inline void override_flag(std::string const& name, bool val) {
+    return provider_->override_flag(name, val);
+}
+
+inline void reset_overrides() {
+    return provider_->reset_overrides();
+}
+
+}
+#endif
+"#;
+
+    const EXPORTED_TEST_HEADER_EXPECTED: &str = r#"
+#ifndef com_android_aconfig_test_HEADER_H
+#define com_android_aconfig_test_HEADER_H
+
+#include <string>
+#include <memory>
+#include <server_configurable_flags/get_flags.h>
+using namespace server_configurable_flags;
+
+namespace com::android::aconfig::test {
+class flag_provider_interface {
+public:
+
+    virtual ~flag_provider_interface() = default;
+
+    virtual bool disabled_ro() = 0;
+
+    virtual bool disabled_rw() = 0;
+
+    virtual bool enabled_ro() = 0;
+
+    virtual bool enabled_rw() = 0;
+
+    virtual void override_flag(std::string const&, bool) {}
+
+    virtual void reset_overrides() {}
+};
+
+extern std::unique_ptr<flag_provider_interface> provider_;
+
+extern std::string const DISABLED_RO;
+extern std::string const DISABLED_RW;
+extern std::string const ENABLED_RO;
+extern std::string const ENABLED_RW;
+
+inline bool disabled_ro() {
+    return provider_->disabled_ro();
+}
+
+inline bool disabled_rw() {
+    return provider_->disabled_rw();
+}
+
+inline bool enabled_ro() {
+    return provider_->enabled_ro();
+}
+
+inline bool enabled_rw() {
+    return provider_->enabled_rw();
+}
+
+inline void override_flag(std::string const& name, bool val) {
+    return provider_->override_flag(name, val);
+}
+
+inline void reset_overrides() {
+    return provider_->reset_overrides();
+}
+
+}
+#endif
+"#;
+
+    const PROD_FLAG_PROVIDER_HEADER_EXPECTED: &str = r#"
+#ifndef com_android_aconfig_test_flag_provider_HEADER_H
+#define com_android_aconfig_test_flag_provider_HEADER_H
+
+#include "com_android_aconfig_test.h"
+
+namespace com::android::aconfig::test {
+class flag_provider : public flag_provider_interface {
+public:
+
+    virtual bool disabled_ro() override {
         return false;
     }
 
-    static const bool disabled_rw() {
+    virtual bool disabled_rw() override {
         return GetServerConfigurableFlag(
             "aconfig_test",
             "com.android.aconfig.test.disabled_rw",
             "false") == "true";
     }
 
-    static const bool enabled_ro() {
+    virtual bool enabled_ro() override {
         return true;
     }
 
-    static const bool enabled_rw() {
+    virtual bool enabled_rw() override {
         return GetServerConfigurableFlag(
             "aconfig_test",
             "com.android.aconfig.test.enabled_rw",
             "true") == "true";
     }
+};
 }
 #endif
 "#;
+
+    const TEST_FLAG_PROVIDER_HEADER_EXPECTED: &str = r#"
+#ifndef com_android_aconfig_test_flag_provider_HEADER_H
+#define com_android_aconfig_test_flag_provider_HEADER_H
+
+#include "com_android_aconfig_test.h"
+
+#include <unordered_map>
+#include <unordered_set>
+#include <cassert>
+
+namespace com::android::aconfig::test {
+class flag_provider : public flag_provider_interface {
+private:
+    std::unordered_map<std::string, bool> overrides_;
+    std::unordered_set<std::string> flag_names_;
+
+public:
+
+    flag_provider()
+        : overrides_(),
+          flag_names_() {
+        flag_names_.insert(DISABLED_RO);
+        flag_names_.insert(DISABLED_RW);
+        flag_names_.insert(ENABLED_RO);
+        flag_names_.insert(ENABLED_RW);
+    }
+
+    virtual bool disabled_ro() override {
+        auto it = overrides_.find(DISABLED_RO);
+        if (it != overrides_.end()) {
+            return it->second;
+        } else {
+            return false;
+        }
+    }
+
+    virtual bool disabled_rw() override {
+        auto it = overrides_.find(DISABLED_RW);
+        if (it != overrides_.end()) {
+            return it->second;
+        } else {
+            return GetServerConfigurableFlag(
+                "aconfig_test",
+                "com.android.aconfig.test.disabled_rw",
+                "false") == "true";
+        }
+    }
+
+    virtual bool enabled_ro() override {
+        auto it = overrides_.find(ENABLED_RO);
+        if (it != overrides_.end()) {
+            return it->second;
+        } else {
+            return true;
+        }
+    }
+
+    virtual bool enabled_rw() override {
+        auto it = overrides_.find(ENABLED_RW);
+        if (it != overrides_.end()) {
+            return it->second;
+        } else {
+            return GetServerConfigurableFlag(
+                "aconfig_test",
+                "com.android.aconfig.test.enabled_rw",
+                "true") == "true";
+        }
+    }
+
+    virtual void override_flag(std::string const& flag, bool val) override {
+        assert(flag_names_.count(flag));
+        overrides_[flag] = val;
+    }
+
+    virtual void reset_overrides() override {
+        overrides_.clear();
+    }
+};
+}
+#endif
+"#;
+
+    const SOURCE_FILE_EXPECTED: &str = r#"
+#include "com_android_aconfig_test.h"
+#include "com_android_aconfig_test_flag_provider.h"
+
+namespace com::android::aconfig::test {
+
+    std::string const DISABLED_RO = "com.android.aconfig.test.disabled_ro";
+    std::string const DISABLED_RW = "com.android.aconfig.test.disabled_rw";
+    std::string const ENABLED_RO = "com.android.aconfig.test.enabled_ro";
+    std::string const ENABLED_RW = "com.android.aconfig.test.enabled_rw";
+
+    std::unique_ptr<flag_provider_interface> provider_ =
+        std::make_unique<flag_provider>();
+}
+"#;
+
+    fn test_generate_cpp_code(mode: CodegenMode) {
+        let parsed_flags = crate::test::parse_test_flags();
+        let generated =
+            generate_cpp_code(crate::test::TEST_PACKAGE, parsed_flags.parsed_flag.iter(), mode)
+                .unwrap();
+        let mut generated_files_map = HashMap::new();
+        for file in generated {
+            generated_files_map.insert(
+                String::from(file.path.to_str().unwrap()),
+                String::from_utf8(file.contents.clone()).unwrap(),
+            );
+        }
+
+        let mut target_file_path = String::from("include/com_android_aconfig_test.h");
+        assert!(generated_files_map.contains_key(&target_file_path));
         assert_eq!(
             None,
             crate::test::first_significant_code_diff(
-                expected,
+                match mode {
-                &String::from_utf8(generated.contents).unwrap()
+                    CodegenMode::Production => EXPORTED_PROD_HEADER_EXPECTED,
+                    CodegenMode::Test => EXPORTED_TEST_HEADER_EXPECTED,
+                },
+                generated_files_map.get(&target_file_path).unwrap()
+            )
+        );
+
+        target_file_path = String::from("com_android_aconfig_test_flag_provider.h");
+        assert!(generated_files_map.contains_key(&target_file_path));
+        assert_eq!(
+            None,
+            crate::test::first_significant_code_diff(
+                match mode {
+                    CodegenMode::Production => PROD_FLAG_PROVIDER_HEADER_EXPECTED,
+                    CodegenMode::Test => TEST_FLAG_PROVIDER_HEADER_EXPECTED,
+                },
+                generated_files_map.get(&target_file_path).unwrap()
+            )
+        );
+
+        target_file_path = String::from("com_android_aconfig_test.cc");
+        assert!(generated_files_map.contains_key(&target_file_path));
+        assert_eq!(
+            None,
+            crate::test::first_significant_code_diff(
+                SOURCE_FILE_EXPECTED,
+                generated_files_map.get(&target_file_path).unwrap()
             )
         );
     }
+
+    #[test]
+    fn test_generate_cpp_code_for_prod() {
+        test_generate_cpp_code(CodegenMode::Production);
+    }
+
+    #[test]
+    fn test_generate_cpp_code_for_test() {
+        test_generate_cpp_code(CodegenMode::Test);
+    }
 }

tools/aconfig/src/commands.rs

@@ -143,12 +143,12 @@ pub fn create_java_lib(mut input: Input, codegen_mode: CodegenMode) -> Result<Ve
     generate_java_code(package, parsed_flags.parsed_flag.iter(), codegen_mode)
 }
 
-pub fn create_cpp_lib(mut input: Input) -> Result<OutputFile> {
+pub fn create_cpp_lib(mut input: Input, codegen_mode: CodegenMode) -> Result<Vec<OutputFile>> {
     let parsed_flags = input.try_parse_flags()?;
     let Some(package) = find_unique_package(&parsed_flags) else {
         bail!("no parsed flags, or the parsed flags use different packages");
     };
-    generate_cpp_code(package, parsed_flags.parsed_flag.iter())
+    generate_cpp_code(package, parsed_flags.parsed_flag.iter(), codegen_mode)
 }
 
 pub fn create_rust_lib(mut input: Input) -> Result<OutputFile> {

tools/aconfig/src/main.rs

@@ -60,7 +60,13 @@ fn cli() -> Command {
         .subcommand(
             Command::new("create-cpp-lib")
                 .arg(Arg::new("cache").long("cache").required(true))
-                .arg(Arg::new("out").long("out").required(true)),
+                .arg(Arg::new("out").long("out").required(true))
+                .arg(
+                    Arg::new("mode")
+                        .long("mode")
+                        .value_parser(EnumValueParser::<commands::CodegenMode>::new())
+                        .default_value("production"),
+                ),
         )
         .subcommand(
             Command::new("create-rust-lib")
@@ -163,9 +169,12 @@ fn main() -> Result<()> {
         }
         Some(("create-cpp-lib", sub_matches)) => {
             let cache = open_single_file(sub_matches, "cache")?;
-            let generated_file = commands::create_cpp_lib(cache)?;
+            let mode = get_required_arg::<CodegenMode>(sub_matches, "mode")?;
+            let generated_files = commands::create_cpp_lib(cache, *mode)?;
             let dir = PathBuf::from(get_required_arg::<String>(sub_matches, "out")?);
-            write_output_file_realtive_to_dir(&dir, &generated_file)?;
+            generated_files
+                .iter()
+                .try_for_each(|file| write_output_file_realtive_to_dir(&dir, file))?;
         }
         Some(("create-rust-lib", sub_matches)) => {
             let cache = open_single_file(sub_matches, "cache")?;

tools/aconfig/templates/cpp_exported_header.template

@@ -0,0 +1,48 @@
+#ifndef {header}_HEADER_H
+#define {header}_HEADER_H
+
+#include <string>
+#include <memory>
+{{ if readwrite }}
+#include <server_configurable_flags/get_flags.h>
+using namespace server_configurable_flags;
+{{ endif }}
+namespace {cpp_namespace} \{
+
+class flag_provider_interface \{
+public:
+    virtual ~flag_provider_interface() = default;
+    {{ for item in class_elements}}
+    virtual bool {item.flag_name}() = 0;
+    {{ endfor }}
+    virtual void override_flag(std::string const&, bool) \{}
+
+    virtual void reset_overrides() \{}
+};
+
+extern std::unique_ptr<flag_provider_interface> provider_;
+{{ for item in class_elements}}
+extern std::string const {item.uppercase_flag_name};{{ endfor }}
+{{ for item in class_elements}}
+inline bool {item.flag_name}() \{
+    {{ if for_prod }}
+    {{ if not item.readwrite- }}
+    return {item.default_value};
+    {{ -else- }}
+    return provider_->{item.flag_name}();
+    {{ -endif }}
+    {{ -else- }}
+    return provider_->{item.flag_name}();
+    {{ -endif }}
+}
+{{ endfor }}
+inline void override_flag(std::string const& name, bool val) \{
+    return provider_->override_flag(name, val);
+}
+
+inline void reset_overrides() \{
+    return provider_->reset_overrides();
+}
+
+}
+#endif

tools/aconfig/templates/cpp_prod_flag_provider.template

@@ -1,12 +1,12 @@
-#ifndef {header}_HEADER_H
+#ifndef {header}_flag_provider_HEADER_H
-#define {header}_HEADER_H
+#define {header}_flag_provider_HEADER_H
-{{ if readwrite }}
+#include "{header}.h"
-#include <server_configurable_flags/get_flags.h>
+
-using namespace server_configurable_flags;
-{{ endif }}
 namespace {cpp_namespace} \{
+class flag_provider : public flag_provider_interface \{
+public:
     {{ for item in class_elements}}
-    static const bool {item.flag_name}() \{
+    virtual bool {item.flag_name}() override \{
         {{ if item.readwrite- }}
         return GetServerConfigurableFlag(
             "{item.device_config_namespace}",
@@ -17,5 +17,6 @@ namespace {cpp_namespace} \{
         {{ -endif }}
     }
     {{ endfor }}
+};
 }
 #endif

tools/aconfig/templates/cpp_source_file.template

@@ -0,0 +1,10 @@
+
+#include "{header}.h"
+#include "{header}_flag_provider.h"
+
+namespace {cpp_namespace} \{
+{{ for item in class_elements}}
+std::string const {item.uppercase_flag_name} = "{item.device_config_flag}";{{ endfor }}
+std::unique_ptr<flag_provider_interface> provider_ =
+    std::make_unique<flag_provider>();
+}

tools/aconfig/templates/cpp_test_flag_provider.template

@@ -0,0 +1,49 @@
+#ifndef {header}_flag_provider_HEADER_H
+#define {header}_flag_provider_HEADER_H
+#include "{header}.h"
+
+#include <unordered_map>
+#include <unordered_set>
+#include <cassert>
+
+namespace {cpp_namespace} \{
+class flag_provider : public flag_provider_interface \{
+private:
+    std::unordered_map<std::string, bool> overrides_;
+    std::unordered_set<std::string> flag_names_;
+
+public:
+    flag_provider()
+        : overrides_(),
+        flag_names_() \{
+        {{ for item in class_elements}}
+        flag_names_.insert({item.uppercase_flag_name});{{ endfor }}
+    }
+    {{ for item in class_elements}}
+    virtual bool {item.flag_name}() override \{
+        auto it = overrides_.find({item.uppercase_flag_name});
+	      if (it != overrides_.end()) \{
+	          return it->second;
+        } else \{
+          {{ if item.readwrite- }}
+          return GetServerConfigurableFlag(
+              "{item.device_config_namespace}",
+              "{item.device_config_flag}",
+              "{item.default_value}") == "true";
+          {{ -else- }}
+              return {item.default_value};
+          {{ -endif }}
+        }
+    }
+    {{ endfor }}
+    virtual void override_flag(std::string const& flag, bool val) override \{
+        assert(flag_names_.count(flag));
+        overrides_[flag] = val;
+    }
+
+    virtual void reset_overrides() override \{
+        overrides_.clear();
+    }
+};
+}
+#endif