rustflags in ./cargo/config.toml being ignored

[pablosichert]

Problem

When having a ./cargo/config.toml file that contains e.g. (commonly used in combination with web-sys)

[build]
rustflags = ["--cfg=web_sys_unstable_apis"]

and running dx serve, the build fails since it does not consider the specified rustflags. Running cargo build succeeds.

Steps To Reproduce

Steps to reproduce the behavior:

• Set up project using default_platform = "fullstack".
• Set rustflags in config.toml.
• Run dx serve on a build that depends on specific rustflags being set.

Expected behavior

dx serve should succeed when cargo build does.

Environment:

• Dioxus version: 0.5.4, latest
• Rust version: 1.76.0, stable
• App platform: fullstack

Questionnaire

• I'm interested in fixing this myself but don't know where to start
• I would like to fix and I have a solution
• I don't have time to fix this right now, but maybe later

[pablosichert]

@ealmloff pointed me to the following locations of interest where dioxus sets the rustflags:

dioxus/packages/cli/src/builder.rs

Line 116 in 1ec6819

.set_rust_flags(rust_flags)

dioxus/packages/cli/src/server/fullstack/mod.rs

Lines 10 to 34 in 1ec6819

	static CLIENT_RUST_FLAGS: &str = "-C debuginfo=none -C strip=debuginfo";
	// The `opt-level=2` increases build times, but can noticeably decrease time
	// between saving changes and being able to interact with an app. The "overall"
	// time difference (between having and not having the optimization) can be
	// almost imperceptible (~1 s) but also can be very noticeable (~6 s) — depends
	// on setup (hardware, OS, browser, idle load).
	static SERVER_RUST_FLAGS: &str = "-C opt-level=2";
	static DEBUG_RUST_FLAG: &str = "-C debug-assertions";
	fn rust_flags(build: &ConfigOptsBuild, base_flags: &str) -> String {
	let mut rust_flags = base_flags.to_string();
	if !build.release {
	rust_flags += " ";
	rust_flags += DEBUG_RUST_FLAG;
	};
	rust_flags
	}
	pub fn client_rust_flags(build: &ConfigOptsBuild) -> String {
	rust_flags(build, CLIENT_RUST_FLAGS)
	}
	pub fn server_rust_flags(build: &ConfigOptsBuild) -> String {
	rust_flags(build, SERVER_RUST_FLAGS)
	}

The Cargo Book states on build.rustflags:

There are four mutually exclusive sources of extra flags. They are checked in order, with the first one being used:

1. CARGO_ENCODED_RUSTFLAGS environment variable.
2. RUSTFLAGS environment variable.
3. All matching target.<triple>.rustflags and target.<cfg>.rustflags config entries joined together.
4. build.rustflags config value.

So this behavior is not entirely unsurprising.

I don't know of any obvious solution, but one (rather elaborate) approach would be to search the hierarchy for config.toml and read the files in Dioxus itself: https://doc.rust-lang.org/cargo/reference/config.html#hierarchical-structure.

[pablosichert]

#2259 seems to be somewhat related.