Handle whitespace properly in rustdoc and rustc options

- Use `cargo rustdoc` and `--config build.rustflags` to preserve whitespace
- Allow passing in additional rustdoc and cargo arguments now that `RUSTDOCFLAGS` isn't dependable

Author: jyn514

crates/metadata/lib.rs

@@ -122,7 +122,8 @@ pub struct Metadata {
     targets: Option<Vec<String>>,
 
     /// List of command line arguments for `rustc`.
-    rustc_args: Option<Vec<String>>,
+    #[serde(default)]
+    rustc_args: Vec<String>,
 
     /// List of command line arguments for `rustdoc`.
     #[serde(default)]
@@ -217,15 +218,22 @@ impl Metadata {
 
     /// Return the arguments that should be passed to `cargo`.
     ///
-    // TODO: maybe it shouldn't?
-    /// This will always include `doc --lib --no-deps`.
+    /// This will always include `rustdoc --lib --`.
     /// This will never include `--target`.
     ///
+    /// You can pass `additional_args` to cargo, as well as `rustdoc_args` to `rustdoc`.
+    /// Do not depend on modifying the `Vec` after it's returned; additional arguments
+    /// appended may be passed to rustdoc instead.
+    ///
     /// Note that this does not necessarily reproduce the HTML _output_ of docs.rs exactly.
     /// For example, the links may point somewhere different than they would on docs.rs.
     /// However, rustdoc will see exactly the same code as it would on docs.rs, even counting `cfg`s.
-    pub fn cargo_args(&self) -> Vec<String> {
-        let mut cargo_args: Vec<String> = vec!["doc".into(), "--lib".into(), "--no-deps".into()];
+    pub fn cargo_args(
+        &self,
+        additional_args: &[impl AsRef<str>],
+        rustdoc_args: &[impl AsRef<str>],
+    ) -> Vec<String> {
+        let mut cargo_args: Vec<String> = vec!["rustdoc".into(), "--lib".into()];
 
         if let Some(features) = &self.features {
             cargo_args.push("--features".into());
@@ -240,22 +248,31 @@ impl Metadata {
             cargo_args.push("--no-default-features".into());
         }
 
+        // Pass `RUSTFLAGS` using `cargo --config`, which handles whitespace correctly.
+        if !self.rustc_args.is_empty() {
+            cargo_args.push("-Z".into());
+            cargo_args.push("unstable-options".into());
+            cargo_args.push("--config".into());
+            let rustflags =
+                toml::to_string(&self.rustc_args).expect("serializing a string should never fail");
+            cargo_args.push(format!("build.rustflags={}", rustflags));
+        }
+
+        cargo_args.extend(additional_args.iter().map(|s| s.as_ref().to_owned()));
+        cargo_args.push("--".into());
+        cargo_args.extend_from_slice(&self.rustdoc_args);
+        cargo_args.extend(rustdoc_args.iter().map(|s| s.as_ref().to_owned()));
         cargo_args
     }
 
     /// Return the environment variables that should be set when building this crate.
     ///
     /// This will always contain at least `RUSTDOCFLAGS="-Z unstable-options"`.
     pub fn environment_variables(&self) -> HashMap<&'static str, String> {
-        let joined = |v: &Option<Vec<_>>| v.as_ref().map(|args| args.join(" ")).unwrap_or_default();
-
         let mut map = HashMap::new();
-        map.insert("RUSTFLAGS", joined(&self.rustc_args));
-        map.insert("RUSTDOCFLAGS", self.rustdoc_args.join(" "));
         // For docs.rs detection from build scripts:
         // https://github.com/rust-lang/docs.rs/issues/147
         map.insert("DOCS_RS", "1".into());
-
         map
     }
 }

src/docbuilder/rustwide_builder.rs

@@ -561,17 +561,16 @@ impl RustwideBuilder {
         target: &str,
         metadata: &Metadata,
         limits: &Limits,
-        rustdoc_flags_extras: Vec<String>,
+        mut rustdoc_flags_extras: Vec<String>,
     ) -> Result<Command<'ws, 'pl>> {
         // If the explicit target is not a tier one target, we need to install it.
         if !docsrs_metadata::DEFAULT_TARGETS.contains(&target) {
             // This is a no-op if the target is already installed.
             self.toolchain.add_target(&self.workspace, target)?;
         }
 
-        let mut cargo_args = metadata.cargo_args();
-
         // Add docs.rs specific arguments
+        let mut cargo_args = Vec::new();
         if let Some(cpu_limit) = self.config.build_cpu_limit {
             cargo_args.push(format!("-j{}", cpu_limit));
         }
@@ -580,18 +579,22 @@ impl RustwideBuilder {
             cargo_args.push(target.into());
         };
 
-        let mut env_vars = metadata.environment_variables();
-        let rustdoc_flags = env_vars.entry("RUSTDOCFLAGS").or_default();
-        // WARNING: this *must* end with a space or it will cause rustdoc to give an error
-        rustdoc_flags
-            .push_str(" --static-root-path / --cap-lints warn --disable-per-crate-search ");
-        rustdoc_flags.push_str(&rustdoc_flags_extras.join(" "));
+        #[rustfmt::skip]
+        const UNCONDITIONAL_ARGS: &[&str] = &[
+            "--static-root-path", "/",
+            "--cap-lints", "warn",
+            "--disable-per-crate-search",
+        ];
+
+        rustdoc_flags_extras.extend(UNCONDITIONAL_ARGS.iter().map(|&s| s.to_owned()));
+        let cargo_args = metadata.cargo_args(&cargo_args, &rustdoc_flags_extras);
 
         let mut command = build
             .cargo()
             .timeout(Some(limits.timeout()))
             .no_output_timeout(None);
-        for (key, val) in env_vars {
+
+        for (key, val) in metadata.environment_variables() {
             command = command.env(key, val);
         }