add an option to pass an arbitrary set of arguments to cargo build

docs/src/commands/build.md

@@ -90,6 +90,17 @@ wasm-pack build examples/js-hello-world --mode no-install
 | `no-install`  | `wasm-pack init` implicitly and create wasm binding  without installing `wasm-bindgen`.  |
 | `normal`      | do all the stuffs of `no-install` with installed `wasm-bindgen`.                         |
 
+## Extra options
+
+The `build` command can pass extra options straight to `cargo build` even if they are not
+supported in wasm-pack. To use them you should add standalone `--` argument at the very
+end of your command, and all the arguments you want to pass to cargo should go after.
+For example to build previous example using unstable cargo offline feature:
+
+```
+wasm-pack build examples/js-hello-world --mode no-install -- -Z offline
+```
+
 <hr style="font-size: 1.5em; margin-top: 2.5em"/>
 
 <sup id="footnote-0">0</sup> If you need to include additional assets in the pkg

src/build.rs

@@ -68,6 +68,7 @@ pub fn cargo_build_wasm(
     path: &Path,
     profile: BuildProfile,
     step: &Step,
+    extra_options: &Vec<String>,
 ) -> Result<(), Error> {
     let msg = format!("{}Compiling to WASM...", emoji::CYCLONE);
     PBAR.step(step, &msg);
@@ -91,6 +92,7 @@ pub fn cargo_build_wasm(
         }
     }
     cmd.arg("--target").arg("wasm32-unknown-unknown");
+    cmd.args(extra_options);
     child::run(log, cmd, "cargo build").context("Compiling your crate to WebAssembly failed")?;
     Ok(())
 }

src/command/build.rs

@@ -31,6 +31,7 @@ pub struct Build {
     pub out_dir: PathBuf,
     pub bindgen: Option<Download>,
     pub cache: Cache,
+    pub extra_options: Vec<String>,
 }
 
 /// The `BuildMode` determines which mode of initialization we are running, and
@@ -120,6 +121,10 @@ pub struct BuildOptions {
     #[structopt(long = "out-dir", short = "d", default_value = "pkg")]
     /// Sets the output directory with a relative path.
     pub out_dir: String,
+
+    #[structopt(last = true)]
+    /// List of extra options to pass to `cargo build`
+    pub extra_options: Vec<String>,
 }
 
 impl Default for BuildOptions {
@@ -135,6 +140,7 @@ impl Default for BuildOptions {
             release: false,
             profiling: false,
             out_dir: String::new(),
+            extra_options: Vec::new(),
         }
     }
 }
@@ -175,6 +181,7 @@ impl Build {
             out_dir,
             bindgen: None,
             cache: Cache::new()?,
+            extra_options: build_opts.extra_options,
         })
     }
 
@@ -283,7 +290,13 @@ impl Build {
 
     fn step_build_wasm(&mut self, step: &Step, log: &Logger) -> Result<(), Error> {
         info!(&log, "Building wasm...");
-        build::cargo_build_wasm(log, &self.crate_path, self.profile, step)?;
+        build::cargo_build_wasm(
+            log,
+            &self.crate_path,
+            self.profile,
+            step,
+            &self.extra_options,
+        )?;
 
         info!(
             &log,

tests/all/build.rs

@@ -248,3 +248,19 @@ fn it_format_out_dir_on_windows() {
         "directories in wasm-pack.log should be well formatted",
     );
 }
+
+#[test]
+fn build_with_arbitrary_cargo_options() {
+    let fixture = utils::fixture::js_hello_world();
+    fixture.install_local_wasm_bindgen();
+
+    let cli = Cli::from_iter_safe(vec![
+        "wasm-pack",
+        "build",
+        &fixture.path.display().to_string(),
+        "--",
+        "--no-default-features",
+    ])
+    .unwrap();
+    fixture.run(cli.cmd).unwrap();
+}