tools/aconfig/src/codegen_rust.rs

/*
 * Copyright (C) 2023 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.
 */

use anyhow::Result;
use serde::Serialize;
use tinytemplate::TinyTemplate;

use crate::aconfig::{FlagState, Permission};
use crate::cache::{Cache, Item};
use crate::commands::OutputFile;

pub fn generate_rust_code(cache: &Cache) -> Result<OutputFile> {
    let package = cache.package();
    let parsed_flags: Vec<TemplateParsedFlag> =
        cache.iter().map(|item| create_template_parsed_flag(package, item)).collect();
    let context = TemplateContext { package: package.to_string(), parsed_flags };
    let mut template = TinyTemplate::new();
    template.add_template("rust_code_gen", include_str!("../templates/rust.template"))?;
    let contents = template.render("rust_code_gen", &context)?;
    let path = ["src", "lib.rs"].iter().collect();
    Ok(OutputFile { contents: contents.into(), path })
}

#[derive(Serialize)]
struct TemplateContext {
    pub package: String,
    pub parsed_flags: Vec<TemplateParsedFlag>,
}

#[derive(Serialize)]
struct TemplateParsedFlag {
    pub name: String,
    pub fn_name: String,

    // TinyTemplate's conditionals are limited to single <bool> expressions; list all options here
    // Invariant: exactly one of these fields will be true
    pub is_read_only_enabled: bool,
    pub is_read_only_disabled: bool,
    pub is_read_write: bool,
}

#[allow(clippy::nonminimal_bool)]
fn create_template_parsed_flag(package: &str, item: &Item) -> TemplateParsedFlag {
    let template = TemplateParsedFlag {
        name: item.name.clone(),
        fn_name: format!("{}_{}", package, &item.name),
        is_read_only_enabled: item.permission == Permission::ReadOnly
            && item.state == FlagState::Enabled,
        is_read_only_disabled: item.permission == Permission::ReadOnly
            && item.state == FlagState::Disabled,
        is_read_write: item.permission == Permission::ReadWrite,
    };
    #[rustfmt::skip]
    debug_assert!(
        (template.is_read_only_enabled && !template.is_read_only_disabled && !template.is_read_write) ||
        (!template.is_read_only_enabled && template.is_read_only_disabled && !template.is_read_write) ||
        (!template.is_read_only_enabled && !template.is_read_only_disabled && template.is_read_write),
        "TemplateParsedFlag invariant failed: {} {} {}",
        template.is_read_only_enabled,
        template.is_read_only_disabled,
        template.is_read_write,
    );
    template
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_generate_rust_code() {
        let cache = crate::test::create_cache();
        let generated = generate_rust_code(&cache).unwrap();
        assert_eq!("src/lib.rs", format!("{}", generated.path.display()));
        let expected = r#"
#[inline(always)]
pub const fn r#test_disabled_ro() -> bool {
    false
}

#[inline(always)]
pub fn r#test_disabled_rw() -> bool {
    flags_rust::GetServerConfigurableFlag("test", "disabled_rw", "false") == "true"
}

#[inline(always)]
pub const fn r#test_enabled_ro() -> bool {
    true
}

#[inline(always)]
pub fn r#test_enabled_rw() -> bool {
    flags_rust::GetServerConfigurableFlag("test", "enabled_rw", "false") == "true"
}
"#;
        assert_eq!(expected.trim(), String::from_utf8(generated.contents).unwrap().trim());
    }
}