EIM-370 embed idf_versions file on build time

[Hahihula]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @Hahihula, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a robust mechanism for handling ESP-IDF version data. It ensures that the application has access to the idf_versions.json file even in scenarios where a direct download might fail. By caching this critical data during the build phase and providing a fallback to this cached data at runtime, the change significantly enhances the application's resilience and offline capabilities regarding IDF version management.

Highlights

• Build-time Caching of IDF Versions: The idf_versions.json file is now downloaded and cached as a compile-time environment variable (CACHED_IDF_VERSIONS) during the application's build process.
• Runtime Fallback Mechanism: If the application fails to download the IDF versions at runtime, it will now gracefully fall back to using the previously cached build-time version, improving resilience and offline capability.
• Asynchronous Build Process: The build script (build.rs) has been updated to use tokio for asynchronous operations, specifically for downloading the IDF versions, making the build process more robust.

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[gemini-code-assist]

Code Review

This pull request introduces a fallback mechanism to use a cached version of idf_versions.json from build time if fetching it at runtime fails. This is a great addition for offline usability. The implementation in build.rs is sound. However, I've found a critical issue in the fallback logic within src/lib/idf_versions.rs that would cause a panic. I've also included a couple of medium-severity suggestions to improve code quality by removing duplication and a minor inefficiency.

[gemini-code-assist]

This fallback logic will fail at runtime. When download_idf_versions fails, build.rs sets CACHED_IDF_VERSIONS to "{}". Deserializing an empty JSON object into the Releases struct will fail because its fields (VERSIONS, IDF_TARGETS, RELEASES) are not marked with #[serde(default)].

To fix this, you need to update the Releases struct definition (around line 32) to allow deserialization from an empty object:

#[derive(Debug, Deserialize, Clone, Default)]
pub struct Releases {
    #[serde(default)]
    pub VERSIONS: Vec<Version>,
    #[serde(default)]
    pub IDF_TARGETS: Vec<IDFTarget>,
    #[serde(default)]
    pub RELEASES: std::collections::HashMap<String, Release>,
}

[gemini-code-assist]

This URL is hardcoded here and also defined as a constant in src/lib/idf_versions.rs. This duplication can lead to inconsistencies. Consider defining the constant in this build script and passing it to the library crate as a compile-time environment variable to maintain a single source of truth.

For example, you could define const IDF_VERSIONS_URL: &str = "..."; at the top of build.rs, use it here, and also pass it to the crate with println!("cargo:rustc-env=IDF_VERSIONS_URL={}", IDF_VERSIONS_URL);. Then, in src/lib/idf_versions.rs, you can define the constant as pub const IDF_VERSIONS_URL: &str = env!("IDF_VERSIONS_URL");.

[Fabricio-ESP]

Confirmed working, offline installation now does not require any internet connection.
Offline packages tested on Windows, Ubuntu and MacOS.