compiler-artifact message doesn't include WASM source maps

[tangmi]

Problem

Hi all, when I compile for --target wasm32-unknown-emscripten (looks like wasm32-unknown-unknown does not support sourcemaps: rust-lang/rust#56660), the compiler-artifact message includes the .js and .wasm files under the filenames property. However, it does not include the .wasm.map file found in target/wasm32-unknown-emscripten/deps/*.wasm.map.

cargo-web depends on the compiler-artifacts message to determine which files to serve for its cargo web start command, but it doesn't seem to serve the .wasm.map file because it is not emitted by cargo.

Steps

When I build with cargo web build --message-format json --target wasm32-unknown-emscripten:

{
    "features": [],
    "filenames": [
        "E:\\test-app\\target\\wasm32-unknown-emscripten\\debug\\test-app.js",
        "E:\\test-app\\target\\wasm32-unknown-emscripten\\debug\\test_app.wasm"
        // Should there be a "target\\wasm32-unknown-emscripten\\debug\\deps\\test_app.wasm.map" here?
    ],
    "fresh": true,
    "package_id": "test-all 0.1.0 (path+file:///E:/test-app)",
    "profile": {
        "debug_assertions": true,
        "debuginfo": 2,
        "opt_level": "0",
        "overflow_checks": true,
        "test": false
    },
    "reason": "compiler-artifact",
    "target": {
        "crate_types": [
            "bin"
        ],
        "edition": "2018",
        "kind": [
            "bin"
        ],
        "name": "test-app",
        "src_path": "E:\\test-app\\src\\main.rs"
    }
}

Possible Solution(s)

Notes

Output of cargo version: cargo 1.35.0-nightly (6f3e9c367 2019-04-04)

Many thanks!

[ehuss]

Do you happen to know exactly when .map files are generated? At a minimum it seems to be related to debug settings.

I also saw a recent post saying the emscripten backend may be changing, would that affect this?

It's a bit unfortunate that we need to hard-code these output files, but neither cargo nor rustc knows about them.