Ethereum development environment for professionals

This is a large release in preparation of the first stable version of Hardhat 3! Please read the list of changes below, the user migration guide, and if you are a plugin author, the plugins migration guide. # Highlights ## New `NetworkManager` methods We deprecated the `network.connect()` method as it was a common source of confusion. It still works, but will eventually be removed. Instead, you can use the new methods `network.create()` and `network.getOrCreate()`. ## Unified compilation of contracts and Solidity tests Previously, Hardhat 3 compiled your contracts and your Solidity tests independently. Starting with this version, they are built together, leading to faster compilation times and smaller compilation artifacts. You can opt into the older behavior with the new `splitTestsCompilation` field in your `solidity` config. This is mainly useful if you rely on plugins that don't yet support unified compilation yet, or if your setup depends on test artifacts being isolated from contract artifacts. ## Simulated networks now return the JSON-RPC code `3` on execution errors If you run an in-process simulated network, or `hardhat node`, revert errors in JSON-RPC responses now use code `3` instead of the code used previously (`-32603` or no code at all). This change aligns Hardhat's behavior with the rest of the tooling ecosystem. This should only improve the error messages that you see, and doesn't require any update, unless you are manually interacting with JSON-RPC responses. ## Proxies support in the `--gas-stats` feature Hardhat now classifies gas stat entries based on both the implementation contract and the proxy (or proxies) in front of it. For example, a proxy forwarding to a `Vault` contract is now reported as gas spent in `Vault` via the proxy. Previously, that same call would have reported all the gas under the proxy, hiding which implementation actually did the work. ## The Hardhat version is now included in the `BuildInfo` files of production builds If you compile your project with the `production` Build Profile, a new `toolVersions` field containing the Hardhat version will be added to your Build Info files. This can help you reproduce your builds in the future. You can enable this functionality in other build profiles with the flag `toolVersionsInBuildInfo`. ## Smaller Build Info output files by using a better default output selector Building your contracts with this version of Hardhat will lead to a significantly smaller `artifacts/` folder, in some cases around 50% smaller. # User migration guide To update to this new version of Hardhat, please follow this guide. ## Replace `network.connect()` with `network.create()`. Replace `network.connect(...)` calls with `network.create(...)`. Everything else keeps working as expected. ## Build ids may change even when bytecode is identical As a result of adding the `toolVersions` field and changing the default output selector, your build ids can change, despite the compilation output's bytecode being identical. If you need to get the exact same version, please downgrade to the previous version. In future `production` builds, you'll always know exactly which version was used, so this should be simpler. # Plugin Migration Guide: Adapting to `splitTestsCompilation: false` This guide covers what `splitTestsCompilation: false` changes for plugin authors and how to adapt. ## Configuration The field is accepted in all object-typed Solidity user configs (`SingleVersionSolidityUserConfig`, `MultiVersionSolidityUserConfig`, `BuildProfilesSolidityUserConfig`). String and string-array configs always resolve to `false`. The resolved value is available at `hre.config.solidity.splitTestsCompilation`. ## Build System (`hre.solidity`)