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Explicitly cargo update in path dependency workspaces.
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Resolves a variant of #167 described here:
#167 (comment)

This issue was observed during a CI run of #900, where an older
tokio-stream version was using a brand-new tokio with stronger
guarantees: several types had newly become `UnwindSafe`.

Since the baseline tokio-stream was a registry version, it was using
a fresh lockfile with the latest dependencies. The current arm,
meanwhile, was a path dependency fixed to a specific commit, where
cargo had decided to reuse an older version of tokio without the
`UnwindSafe` trait on those types.

This presented as a (phantom) breaking change: the older tokio-stream's
types were `UnwindSafe` due to auto-trait propagation from a newer tokio
while the newer tokio-stream with an older tokio did not have that trait.

The solution is to explicitly run `cargo update` inside path dependency
workspaces we create. This way, both path dependency and index-based
rustdoc JSON generation happens with the latest versions of the target
library's own dependencies.
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@obi1kenobi
obi1kenobi committed Sep 2, 2024
1 parent 2466f7c commit 9b1139f
Showing 1 changed file with 133 additions and 31 deletions.
164 changes: 133 additions & 31 deletions src/rustdoc_cmd.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,10 @@ impl RustdocCommand {
crate_source: &CrateSource,
crate_data: &CrateDataForRustdoc,
) -> anyhow::Result<std::path::PathBuf> {
let crate_name = crate_source.name()?;
let version = crate_source.version()?;
let pkg_spec = format!("{crate_name}@{version}");

// Generate an empty placeholder project with a dependency on the crate
// whose rustdoc we need. We take this indirect generation path to avoid issues like:
// https://github.com/obi1kenobi/cargo-semver-checks/issues/167#issuecomment-1382367128
Expand All @@ -62,6 +66,100 @@ impl RustdocCommand {
let placeholder_manifest_path =
save_placeholder_rustdoc_manifest(build_dir.as_path(), placeholder_manifest)
.context("failed to save placeholder rustdoc manifest")?;
if matches!(crate_source, CrateSource::Registry { .. }) {
// We have to run `cargo update` inside the newly-generated project, to ensure
// all dependencies of the library we're scanning are up-to-date.
//
// Otherwise, we risk having a newer version of a dependency in the baseline arm,
// and an older version of the same dependency in the current arm. If that dependency
// started providing stronger guarantees in the newer version, such as newly starting
// to implementing an auto-trait on an existing type, the baseline could contain
// types that inherit that stronger guarantee whereas the current would not.
// That would be reported as a breaking change -- incorrectly so.
//
// cargo does not guarantee it'll update dependencies to a newer lockfile
// if using a path dependency. This bit us in this case:
// https://github.com/obi1kenobi/cargo-semver-checks/issues/167#issuecomment-2324959305
let stderr = if self.silence {
std::process::Stdio::piped()
} else {
// Print cargo update progress
std::process::Stdio::inherit()
};

let mut cmd = std::process::Command::new("cargo");
cmd.stdout(std::process::Stdio::null()) // Don't pollute output
.stderr(stderr)
.current_dir(build_dir.as_path())
.arg("update")
.arg("--manifest-path")
.arg(&placeholder_manifest_path);

// Respect our configured color choice.
cmd.arg(if config.err_color_choice() {
"--color=always"
} else {
"--color=never"
});

let output = cmd.output()?;
if !output.status.success() {
if self.silence {
config.log_error(|config| {
let mut stderr = config.stderr();
let delimiter = "-----";
writeln!(
stderr,
"error: running 'cargo update' on crate {crate_name} failed with output:"
)?;
writeln!(
stderr,
"{delimiter}\n{}\n{delimiter}\n",
String::from_utf8_lossy(&output.stderr)
)?;
writeln!(
stderr,
"error: failed to update dependencies for crate {crate_name} v{version}"
)?;
Ok(())
})?;
} else {
config.log_error(|config| {
writeln!(
config.stderr(),
"error: running 'cargo update' on crate {crate_name} v{version} failed, see stderr output above"
)?;
Ok(())
})?;
}
config.log_error(|config| {
let features =
crate_source.feature_list_from_config(config, crate_data.feature_config);
let mut stderr = config.stderr();
writeln!(
stderr,
"note: this is unlikely to be a bug in cargo-semver-checks,"
)?;
writeln!(
stderr,
" and is probably an issue with the crate's Cargo.toml"
)?;
writeln!(
stderr,
"note: the following command can be used to reproduce the compilation error:"
)?;
let repro_base = produce_repro_workspace(crate_name, crate_source, &features);
writeln!(
stderr,
"{repro_base}cargo update\n"
)?;
Ok(())
})?;
anyhow::bail!(
"aborting due to failure to run 'cargo update' for crate {crate_name} v{version}"
);
}
}

let metadata = cargo_metadata::MetadataCommand::new()
.manifest_path(&placeholder_manifest_path)
Expand All @@ -82,10 +180,6 @@ impl RustdocCommand {
std::process::Stdio::inherit()
};

let crate_name = crate_source.name()?;
let version = crate_source.version()?;
let pkg_spec = format!("{crate_name}@{version}");

// Generating rustdoc JSON for a crate also involves checking that crate's dependencies.
// The check is done by rustc, not rustdoc, so it's subject to RUSTFLAGS not RUSTDOCFLAGS.
// We don't want rustc to fail that check if the user has set RUSTFLAGS="-Dwarnings" here.
Expand Down Expand Up @@ -130,7 +224,7 @@ impl RustdocCommand {
cmd.arg("--no-deps");
}

// respect our configured color choice
// Respect our configured color choice
cmd.arg(if config.err_color_choice() {
"--color=always"
} else {
Expand Down Expand Up @@ -183,32 +277,8 @@ impl RustdocCommand {
stderr,
"note: the following command can be used to reproduce the compilation error:"
)?;
let selector = match crate_source {
CrateSource::Registry { version, .. } => format!("{crate_name}@={version}"),
CrateSource::ManifestPath { manifest } => format!(
"--path {}",
manifest
.path
.parent()
.expect("source Cargo.toml had no parent path")
.to_str()
.expect("failed to create path string")
),
};
let feature_list = if features.is_empty() {
"".to_string()
} else {
format!("--features {} ", features.into_iter().join(","))
};
writeln!(
stderr,
" \
cargo new --lib example &&
cd example &&
echo '[workspace]' >> Cargo.toml &&
cargo add {selector} --no-default-features {feature_list}&&
cargo check\n"
)?;
let repro_base = produce_repro_workspace(crate_name, crate_source, &features);
writeln!(stderr, "{repro_base}cargo check\n")?;
Ok(())
})?;
anyhow::bail!(
Expand Down Expand Up @@ -345,6 +415,38 @@ in the metadata and stderr didn't mention it was lacking a lib target. This is p
}
}

fn produce_repro_workspace(
crate_name: &str,
crate_source: &CrateSource,
features: &[String],
) -> String {
let selector = match crate_source {
CrateSource::Registry { version, .. } => format!("{crate_name}@={version}"),
CrateSource::ManifestPath { manifest } => format!(
"--path {}",
manifest
.path
.parent()
.expect("source Cargo.toml had no parent path")
.to_str()
.expect("failed to create path string")
),
};
let feature_list = if features.is_empty() {
"".to_string()
} else {
format!("--features {} ", features.iter().join(","))
};
format!(
" \
cargo new --lib example &&
cd example &&
echo '[workspace]' >> Cargo.toml &&
cargo add {selector} --no-default-features {feature_list}&&
"
)
}

impl Default for RustdocCommand {
fn default() -> Self {
Self::new()
Expand Down

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