[bug] tauri-build build script always rebuild if tauri.conf.json is missing

[CrendKing]

Describe the bug

When only using Tauri.toml for the config file, the build script always rebuilds the final executable even nothing is changed. This is due to the usage of unconditional cargo:rerun-if-changed=tauri.conf.json in the build function. Since there is no tauri.conf.json file, and rerun-if-changed considers missing file the same as "stale file", it always triggers the rerun.

Removing the unconditional println!("cargo:rerun-if-changed=tauri.conf.json") line, or placing a duplicate tauri.conf.json in the project bypasses the problem.

Reproduction

Simply switch to use the Tauri.toml file (and of course the config-toml feature). Build the project, then build it again without changing anything.

Expected behavior

There should be no rebuild triggering.

Full tauri info output

[✔] Environment
    - OS: Windows 10.0.22631 X64
    ✔ WebView2: 121.0.2277.83
    ✔ MSVC: Visual Studio Build Tools 2022
    ✔ rustc: 1.75.0 (82e1608df 2023-12-21)
    ✔ cargo: 1.75.0 (1d8b05cdd 2023-11-20)
    ✔ rustup: 1.26.0 (5af9b9484 2023-04-05)
    ✔ Rust toolchain: stable-x86_64-pc-windows-msvc (environment override by RUSTUP_TOOLCHAIN)
    - node: 20.11.0
    - pnpm: 8.15.1
    - npm: 10.2.4

[-] Packages
    - tauri-cli [RUST]: 2.0.0-alpha.21

Stack trace

No response

Additional context

I think the default tauri.conf.json should have its own feature, just like config-toml, and make it default in Cargo. Then we can conditionally include the rerun line with a #[cfg(feature)].

[naman-crabnebula]

In my opinion, adding an empty tauri.conf.json file at the build time would be a better option, because tauri.conf.json is the default config file, and the tauri.toml or tauri.conf.json5 are just additional features.

So, if a user deletes the tauri.conf.json file.

And thanks for reporting the bug btw.

[CrendKing]

In principle, I really dislike ambiguous logic/environment/etc, because it causes confusion. 3 months later when I revisit this project and see both tauri.conf.json and Tauri.toml, especially the former being {} (but can't be completely empty because then the build complains unable to parse JSON Tauri config file at <path>\src-tauri\tauri.conf.json because EOF while parsing a value at line 1 column 0 for some reason), I will force myself to spend some time recollect the memory we are having here. I will have to ask myself why there are two config files where one is completely unused just for arbitrary Tauri rule that can be found nowhere else.

But if you guys really want to keep the empty tauri.conf.json, please document this behavior in https://tauri.app/v1/references/configuration-files. There is currently no mentioning that by switching the non-default option and deleting the old file, it causes side-effect.

[naman-crabnebula]

But if you guys really want to keep the empty tauri.conf.json, please document this behavior in https://tauri.app/v1/references/configuration-files. There is currently no mentioning that by switching the non-default option and deleting the old file, it causes side-effect

Yeah, because that's a bug 😅

Don't worry, we will fix it ASAP and consider all the odds.

Thank You

[amrbashir]

I think the default tauri.conf.json should have its own feature, just like config-toml, and make it default in Cargo. Then we can conditionally include the rerun line with a #[cfg(feature)].

I agree, this should be the solution

[CrendKing]

Actually, according to my test, if tauri.conf.json exists, Tauri will completely ignore the config-toml feature, and always use tauri.conf.json. So having an empty tauri.conf.json won't work. It needs to be an exact duplicate at the moment.

I see you are making #8732. Thank you so much! However, I do not know where in tauri-build is the logic that the presence of tauri.conf.json overrides everything. It might be a potential source of bug. Just FYI.