Use released DotSlash package for argument-comment lint (#15199)

## Why The argument-comment lint now has a packaged DotSlash artifact from [#15198](https://github.com/openai/codex/pull/15198), so the normal repo lint path should use that released payload instead of rebuilding the lint from source every time. That keeps `just clippy` and CI aligned with the shipped artifact while preserving a separate source-build path for people actively hacking on the lint crate. The current alpha package also exposed two integration wrinkles that the repo-side prebuilt wrapper needs to smooth over: - the bundled Dylint library filename includes the host triple, for example `@nightly-2025-09-18-aarch64-apple-darwin`, and Dylint derives `RUSTUP_TOOLCHAIN` from that filename - on Windows, Dylint's driver path also expects `RUSTUP_HOME` to be present in the environment Without those adjustments, the prebuilt CI jobs fail during `cargo metadata` or driver setup. This change makes the checked-in prebuilt wrapper normalize the packaged library name to the plain `nightly-2025-09-18` channel before invoking `cargo-dylint`, and it teaches both the wrapper and the packaged runner source to infer `RUSTUP_HOME` from `rustup show home` when the environment does not already provide it. After the prebuilt Windows lint job started running successfully, it also surfaced a handful of existing anonymous literal callsites in `windows-sandbox-rs`. This PR now annotates those callsites so the new cross-platform lint job is green on the current tree. ## What Changed - checked in the current `tools/argument-comment-lint/argument-comment-lint` DotSlash manifest - kept `tools/argument-comment-lint/run.sh` as the source-build wrapper for lint development - added `tools/argument-comment-lint/run-prebuilt-linter.sh` as the normal enforcement path, using the checked-in DotSlash package and bundled `cargo-dylint` - updated `just clippy` and `just argument-comment-lint` to use the prebuilt wrapper - split `.github/workflows/rust-ci.yml` so source-package checks live in a dedicated `argument_comment_lint_package` job, while the released lint runs in an `argument_comment_lint_prebuilt` matrix on Linux, macOS, and Windows - kept the pinned `nightly-2025-09-18` toolchain install in the prebuilt CI matrix, since the prebuilt package still relies on rustup-provided toolchain components - updated `tools/argument-comment-lint/run-prebuilt-linter.sh` to normalize host-qualified nightly library filenames, keep the `rustup` shim directory ahead of direct toolchain `cargo` binaries, and export `RUSTUP_HOME` when needed for Windows Dylint driver setup - updated `tools/argument-comment-lint/src/bin/argument-comment-lint.rs` so future published DotSlash artifacts apply the same nightly-filename normalization and `RUSTUP_HOME` inference internally - fixed the remaining Windows lint violations in `codex-rs/windows-sandbox-rs` by adding the required `/*param*/` comments at the reported callsites - documented the checked-in DotSlash file, wrapper split, archive layout, nightly prerequisite, and Windows `RUSTUP_HOME` requirement in `tools/argument-comment-lint/README.md`
2026-05-03 21:01:55 +03:00 · 2026-03-19 20:19:22 -07:00
parent 96a86710c3
commit fa2a2f0be9
29 changed files with 723 additions and 158 deletions
--- a/tools/argument-comment-lint/README.md
+++ b/tools/argument-comment-lint/README.md
@@ -73,21 +73,71 @@ GitHub releases also publish a DotSlash file named
 x64. The published package contains a small runner executable, a bundled
 `cargo-dylint`, and the prebuilt lint library.

-Run the lint against `codex-rs` from the repo root:
+The package is not a full Rust toolchain. Running the prebuilt path still
+requires the pinned nightly toolchain to be installed via `rustup`:
+
+```bash
+rustup toolchain install nightly-2025-09-18 \
+  --component llvm-tools-preview \
+  --component rustc-dev \
+  --component rust-src
+```
+
+The checked-in DotSlash file lives at `tools/argument-comment-lint/argument-comment-lint`.
+`run-prebuilt-linter.sh` resolves that file via `dotslash` and is the path used by
+`just clippy`, `just argument-comment-lint`, and the Rust CI job. The
+source-build path remains available in `run.sh` for people
+iterating on the lint crate itself.
+
+The Unix archive layout is:
+
+```text
+argument-comment-lint/
+  bin/
+    argument-comment-lint
+    cargo-dylint
+  lib/
+    libargument_comment_lint@nightly-2025-09-18-<target>.dylib|so
+```
+
+On Windows the same layout is published as a `.zip`, with `.exe` and `.dll`
+filenames instead.
+
+DotSlash resolves the package entrypoint to `argument-comment-lint/bin/argument-comment-lint`
+(or `.exe` on Windows). That runner finds the sibling bundled `cargo-dylint`
+binary and the single packaged Dylint library under `lib/`, normalizes the
+host-qualified nightly filename to the plain `nightly-2025-09-18` channel when
+needed, and then invokes `cargo-dylint dylint --lib-path <that-library>` with
+the repo's default `DYLINT_RUSTFLAGS` and `CARGO_INCREMENTAL=0` settings.
+
+The checked-in `run-prebuilt-linter.sh` wrapper uses the fetched package
+contents directly so the current checked-in alpha artifact works the same way.
+It also makes sure the `rustup` shims stay ahead of any direct toolchain
+`cargo` binary on `PATH`, and sets `RUSTUP_HOME` from `rustup show home` when
+the environment does not already provide it. That extra `RUSTUP_HOME` export is
+required for the current Windows Dylint driver path.
+
+If you are changing the lint crate itself, use the source-build wrapper:

 ```bash
 ./tools/argument-comment-lint/run.sh -p codex-core
+```
+
+Run the lint against `codex-rs` from the repo root:
+
+```bash
+./tools/argument-comment-lint/run-prebuilt-linter.sh -p codex-core
 just argument-comment-lint -p codex-core
 ```

-If no package selection is provided, `run.sh` defaults to checking the
+If no package selection is provided, `run-prebuilt-linter.sh` defaults to checking the
 `codex-rs` workspace with `--workspace --no-deps`.

 Repo runs also promote `uncommented_anonymous_literal_argument` to an error by
 default:

 ```bash
-./tools/argument-comment-lint/run.sh -p codex-core
+./tools/argument-comment-lint/run-prebuilt-linter.sh -p codex-core
 ```

 The wrapper does that by setting `DYLINT_RUSTFLAGS`, and it leaves an explicit
@@ -105,5 +155,5 @@ CARGO_INCREMENTAL=1 \
 To expand target coverage for an ad hoc run:

 ```bash
-./tools/argument-comment-lint/run.sh -p codex-core -- --all-targets
+./tools/argument-comment-lint/run-prebuilt-linter.sh -p codex-core -- --all-targets
 ```
--- a/tools/argument-comment-lint/argument-comment-lint
+++ b/tools/argument-comment-lint/argument-comment-lint
@@ -0,0 +1,79 @@
+#!/usr/bin/env dotslash
+
+{
+  "name": "argument-comment-lint",
+  "platforms": {
+    "macos-aarch64": {
+      "size": 3402747,
+      "hash": "blake3",
+      "digest": "a11669d2f184a2c6f226cedce1bf10d1ec478d53413c42fe80d17dd873fdb2d7",
+      "format": "tar.gz",
+      "path": "argument-comment-lint/bin/argument-comment-lint",
+      "providers": [
+        {
+          "url": "https://github.com/openai/codex/releases/download/rust-v0.117.0-alpha.2/argument-comment-lint-aarch64-apple-darwin.tar.gz"
+        },
+        {
+          "type": "github-release",
+          "repo": "https://github.com/openai/codex",
+          "tag": "rust-v0.117.0-alpha.2",
+          "name": "argument-comment-lint-aarch64-apple-darwin.tar.gz"
+        }
+      ]
+    },
+    "linux-x86_64": {
+      "size": 3869711,
+      "hash": "blake3",
+      "digest": "1015f4ba07d57edc5ec79c8f6709ddc1516f64c903e909820437a4b89d8d853a",
+      "format": "tar.gz",
+      "path": "argument-comment-lint/bin/argument-comment-lint",
+      "providers": [
+        {
+          "url": "https://github.com/openai/codex/releases/download/rust-v0.117.0-alpha.2/argument-comment-lint-x86_64-unknown-linux-gnu.tar.gz"
+        },
+        {
+          "type": "github-release",
+          "repo": "https://github.com/openai/codex",
+          "tag": "rust-v0.117.0-alpha.2",
+          "name": "argument-comment-lint-x86_64-unknown-linux-gnu.tar.gz"
+        }
+      ]
+    },
+    "linux-aarch64": {
+      "size": 3759446,
+      "hash": "blake3",
+      "digest": "91f2a31e6390ca728ad09ae1aa6b6f379c67d996efcc22956001df89f068af5b",
+      "format": "tar.gz",
+      "path": "argument-comment-lint/bin/argument-comment-lint",
+      "providers": [
+        {
+          "url": "https://github.com/openai/codex/releases/download/rust-v0.117.0-alpha.2/argument-comment-lint-aarch64-unknown-linux-gnu.tar.gz"
+        },
+        {
+          "type": "github-release",
+          "repo": "https://github.com/openai/codex",
+          "tag": "rust-v0.117.0-alpha.2",
+          "name": "argument-comment-lint-aarch64-unknown-linux-gnu.tar.gz"
+        }
+      ]
+    },
+    "windows-x86_64": {
+      "size": 3244599,
+      "hash": "blake3",
+      "digest": "dc711c6d85b1cabbe52447dda3872deb20c2e64b155da8be0ecb207c7c391683",
+      "format": "zip",
+      "path": "argument-comment-lint/bin/argument-comment-lint.exe",
+      "providers": [
+        {
+          "url": "https://github.com/openai/codex/releases/download/rust-v0.117.0-alpha.2/argument-comment-lint-x86_64-pc-windows-msvc.zip"
+        },
+        {
+          "type": "github-release",
+          "repo": "https://github.com/openai/codex",
+          "tag": "rust-v0.117.0-alpha.2",
+          "name": "argument-comment-lint-x86_64-pc-windows-msvc.zip"
+        }
+      ]
+    }
+  }
+}
--- a/tools/argument-comment-lint/run-prebuilt-linter.sh
+++ b/tools/argument-comment-lint/run-prebuilt-linter.sh
@@ -0,0 +1,164 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+manifest_path="$repo_root/codex-rs/Cargo.toml"
+dotslash_manifest="$repo_root/tools/argument-comment-lint/argument-comment-lint"
+
+has_manifest_path=false
+has_package_selection=false
+has_library_selection=false
+has_no_deps=false
+expect_value=""
+
+for arg in "$@"; do
+    if [[ -n "$expect_value" ]]; then
+        case "$expect_value" in
+            manifest_path)
+                has_manifest_path=true
+                ;;
+            package_selection)
+                has_package_selection=true
+                ;;
+            library_selection)
+                has_library_selection=true
+                ;;
+        esac
+        expect_value=""
+        continue
+    fi
+
+    case "$arg" in
+        --)
+            break
+            ;;
+        --manifest-path)
+            expect_value="manifest_path"
+            ;;
+        --manifest-path=*)
+            has_manifest_path=true
+            ;;
+        -p|--package)
+            expect_value="package_selection"
+            ;;
+        --package=*)
+            has_package_selection=true
+            ;;
+        --lib|--lib-path)
+            expect_value="library_selection"
+            ;;
+        --lib=*|--lib-path=*)
+            has_library_selection=true
+            ;;
+        --workspace)
+            has_package_selection=true
+            ;;
+        --no-deps)
+            has_no_deps=true
+            ;;
+    esac
+done
+
+lint_args=()
+if [[ "$has_manifest_path" == false ]]; then
+    lint_args+=(--manifest-path "$manifest_path")
+fi
+if [[ "$has_package_selection" == false ]]; then
+    lint_args+=(--workspace)
+fi
+if [[ "$has_no_deps" == false ]]; then
+    lint_args+=(--no-deps)
+fi
+lint_args+=("$@")
+
+if ! command -v dotslash >/dev/null 2>&1; then
+    cat >&2 <<EOF
+argument-comment-lint prebuilt wrapper requires dotslash.
+Install dotslash, or use:
+  ./tools/argument-comment-lint/run.sh ...
+EOF
+    exit 1
+fi
+
+if command -v rustup >/dev/null 2>&1; then
+    rustup_bin_dir="$(dirname "$(command -v rustup)")"
+    path_entries=()
+    while IFS= read -r entry; do
+        [[ -n "$entry" && "$entry" != "$rustup_bin_dir" ]] && path_entries+=("$entry")
+    done < <(printf '%s\n' "${PATH//:/$'\n'}")
+    PATH="$rustup_bin_dir"
+    if ((${#path_entries[@]} > 0)); then
+        PATH+=":$(IFS=:; echo "${path_entries[*]}")"
+    fi
+    export PATH
+
+    if [[ -z "${RUSTUP_HOME:-}" ]]; then
+        rustup_home="$(rustup show home 2>/dev/null || true)"
+        if [[ -n "$rustup_home" ]]; then
+            export RUSTUP_HOME="$rustup_home"
+        fi
+    fi
+fi
+
+package_entrypoint="$(dotslash -- fetch "$dotslash_manifest")"
+bin_dir="$(cd "$(dirname "$package_entrypoint")" && pwd)"
+package_root="$(cd "$bin_dir/.." && pwd)"
+library_dir="$package_root/lib"
+
+cargo_dylint="$bin_dir/cargo-dylint"
+if [[ ! -x "$cargo_dylint" ]]; then
+    cargo_dylint="$bin_dir/cargo-dylint.exe"
+fi
+if [[ ! -x "$cargo_dylint" ]]; then
+    echo "bundled cargo-dylint executable not found under $bin_dir" >&2
+    exit 1
+fi
+
+shopt -s nullglob
+libraries=("$library_dir"/*@*)
+shopt -u nullglob
+if [[ ${#libraries[@]} -eq 0 ]]; then
+    echo "no packaged Dylint library found in $library_dir" >&2
+    exit 1
+fi
+if [[ ${#libraries[@]} -ne 1 ]]; then
+    echo "expected exactly one packaged Dylint library in $library_dir" >&2
+    exit 1
+fi
+
+library_path="${libraries[0]}"
+library_filename="$(basename "$library_path")"
+normalized_library_path="$library_path"
+library_ext=".${library_filename##*.}"
+library_stem="${library_filename%.*}"
+if [[ "$library_stem" =~ ^(.+@nightly-[0-9]{4}-[0-9]{2}-[0-9]{2})-.+$ ]]; then
+    normalized_library_filename="${BASH_REMATCH[1]}$library_ext"
+    temp_dir="$(mktemp -d "${TMPDIR:-/tmp}/argument-comment-lint.XXXXXX")"
+    normalized_library_path="$temp_dir/$normalized_library_filename"
+    cp "$library_path" "$normalized_library_path"
+fi
+
+if [[ -n "${DYLINT_RUSTFLAGS:-}" ]]; then
+    if [[ "$DYLINT_RUSTFLAGS" != *"-D uncommented-anonymous-literal-argument"* ]]; then
+        DYLINT_RUSTFLAGS+=" -D uncommented-anonymous-literal-argument"
+    fi
+    if [[ "$DYLINT_RUSTFLAGS" != *"-A unknown_lints"* ]]; then
+        DYLINT_RUSTFLAGS+=" -A unknown_lints"
+    fi
+else
+    DYLINT_RUSTFLAGS="-D uncommented-anonymous-literal-argument -A unknown_lints"
+fi
+export DYLINT_RUSTFLAGS
+
+if [[ -z "${CARGO_INCREMENTAL:-}" ]]; then
+    export CARGO_INCREMENTAL=0
+fi
+
+command=("$cargo_dylint" dylint --lib-path "$normalized_library_path")
+if [[ "$has_library_selection" == false ]]; then
+    command+=(--all)
+fi
+command+=("${lint_args[@]}")
+
+exec "${command[@]}"
--- a/tools/argument-comment-lint/run.sh
+++ b/tools/argument-comment-lint/run.sh
@@ -5,6 +5,7 @@ set -euo pipefail
 repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
 lint_path="$repo_root/tools/argument-comment-lint"
 manifest_path="$repo_root/codex-rs/Cargo.toml"
+toolchain_channel="nightly-2025-09-18"
 strict_lint="uncommented-anonymous-literal-argument"
 noise_lint="unknown_lints"

@@ -14,6 +15,42 @@ has_no_deps=false
 has_library_selection=false
 expect_value=""

+ensure_local_prerequisites() {
+    if ! command -v cargo-dylint >/dev/null 2>&1 || ! command -v dylint-link >/dev/null 2>&1; then
+        cat >&2 <<EOF
+argument-comment-lint source wrapper requires cargo-dylint and dylint-link.
+Install them with:
+  cargo install --locked cargo-dylint dylint-link
+EOF
+        exit 1
+    fi
+
+    if ! rustup toolchain list | grep -q "^${toolchain_channel}"; then
+        cat >&2 <<EOF
+argument-comment-lint source wrapper requires the ${toolchain_channel} toolchain with rustc-dev support.
+Install it with:
+  rustup toolchain install ${toolchain_channel} \\
+    --component llvm-tools-preview \\
+    --component rustc-dev \\
+    --component rust-src
+EOF
+        exit 1
+    fi
+}
+
+set_default_env() {
+    if [[ "${DYLINT_RUSTFLAGS:-}" != *"$strict_lint"* ]]; then
+        export DYLINT_RUSTFLAGS="${DYLINT_RUSTFLAGS:+${DYLINT_RUSTFLAGS} }-D $strict_lint"
+    fi
+    if [[ "${DYLINT_RUSTFLAGS:-}" != *"$noise_lint"* ]]; then
+        export DYLINT_RUSTFLAGS="${DYLINT_RUSTFLAGS:+${DYLINT_RUSTFLAGS} }-A $noise_lint"
+    fi
+
+    if [[ -z "${CARGO_INCREMENTAL:-}" ]]; then
+        export CARGO_INCREMENTAL=0
+    fi
+}
+
 for arg in "$@"; do
    if [[ -n "$expect_value" ]]; then
        case "$expect_value" in
@@ -62,30 +99,25 @@ for arg in "$@"; do
    esac
 done

+lint_args=()
+if [[ "$has_manifest_path" == false ]]; then
+    lint_args+=(--manifest-path "$manifest_path")
+fi
+if [[ "$has_package_selection" == false ]]; then
+    lint_args+=(--workspace)
+fi
+if [[ "$has_no_deps" == false ]]; then
+    lint_args+=(--no-deps)
+fi
+lint_args+=("$@")
+
+ensure_local_prerequisites
+set_default_env
+
 cmd=(cargo dylint --path "$lint_path")
 if [[ "$has_library_selection" == false ]]; then
    cmd+=(--all)
 fi
-if [[ "$has_manifest_path" == false ]]; then
-    cmd+=(--manifest-path "$manifest_path")
-fi
-if [[ "$has_package_selection" == false ]]; then
-    cmd+=(--workspace)
-fi
-if [[ "$has_no_deps" == false ]]; then
-    cmd+=(--no-deps)
-fi
-cmd+=("$@")
-
-if [[ "${DYLINT_RUSTFLAGS:-}" != *"$strict_lint"* ]]; then
-    export DYLINT_RUSTFLAGS="${DYLINT_RUSTFLAGS:+${DYLINT_RUSTFLAGS} }-D $strict_lint"
-fi
-if [[ "${DYLINT_RUSTFLAGS:-}" != *"$noise_lint"* ]]; then
-    export DYLINT_RUSTFLAGS="${DYLINT_RUSTFLAGS:+${DYLINT_RUSTFLAGS} }-A $noise_lint"
-fi
-
-if [[ -z "${CARGO_INCREMENTAL:-}" ]]; then
-    export CARGO_INCREMENTAL=0
-fi
+cmd+=("${lint_args[@]}")

 exec "${cmd[@]}"
--- a/tools/argument-comment-lint/src/bin/argument-comment-lint.rs
+++ b/tools/argument-comment-lint/src/bin/argument-comment-lint.rs
@@ -5,6 +5,8 @@ use std::path::Path;
 use std::path::PathBuf;
 use std::process::Command;
 use std::process::ExitCode;
+use std::time::SystemTime;
+use std::time::UNIX_EPOCH;

 fn main() -> ExitCode {
    match run() {
@@ -33,7 +35,7 @@ fn run() -> Result<ExitCode, String> {
    })?;
    let cargo_dylint = bin_dir.join(cargo_dylint_binary_name());
    let library_dir = package_root.join("lib");
-    let library_path = find_bundled_library(&library_dir)?;
+    let library_path = prepare_library_path_for_dylint(&find_bundled_library(&library_dir)?)?;

    ensure_exists(&cargo_dylint, "bundled cargo-dylint executable")?;
    ensure_exists(
@@ -49,7 +51,7 @@ fn run() -> Result<ExitCode, String> {
        command.arg("--all");
    }
    command.args(&args);
-    set_default_env(&mut command);
+    set_default_env(&mut command)?;

    let status = command
        .status()
@@ -80,7 +82,7 @@ fn has_library_selection(args: &[OsString]) -> bool {
    false
 }

-fn set_default_env(command: &mut Command) {
+fn set_default_env(command: &mut Command) -> Result<(), String> {
    if let Some(flags) = env::var_os("DYLINT_RUSTFLAGS") {
        let mut flags = flags.to_string_lossy().to_string();
        append_flag_if_missing(&mut flags, "-D uncommented-anonymous-literal-argument");
@@ -96,6 +98,14 @@ fn set_default_env(command: &mut Command) {
    if env::var_os("CARGO_INCREMENTAL").is_none() {
        command.env("CARGO_INCREMENTAL", "0");
    }
+
+    if env::var_os("RUSTUP_HOME").is_none()
+        && let Some(rustup_home) = infer_rustup_home()?
+    {
+        command.env("RUSTUP_HOME", rustup_home);
+    }
+
+    Ok(())
 }

 fn append_flag_if_missing(flags: &mut String, flag: &str) {
@@ -117,6 +127,28 @@ fn cargo_dylint_binary_name() -> &'static str {
    }
 }

+fn infer_rustup_home() -> Result<Option<OsString>, String> {
+    let output = Command::new("rustup")
+        .args(["show", "home"])
+        .output()
+        .map_err(|err| format!("failed to query rustup home via `rustup show home`: {err}"))?;
+    if !output.status.success() {
+        return Err(format!(
+            "`rustup show home` failed: {}",
+            String::from_utf8_lossy(&output.stderr).trim()
+        ));
+    }
+
+    let home = String::from_utf8(output.stdout)
+        .map_err(|err| format!("`rustup show home` returned invalid UTF-8: {err}"))?;
+    let home = home.trim();
+    if home.is_empty() {
+        Ok(None)
+    } else {
+        Ok(Some(OsString::from(home)))
+    }
+}
+
 fn ensure_exists(path: &Path, label: &str) -> Result<(), String> {
    if path.exists() {
        Ok(())
@@ -158,7 +190,90 @@ fn find_bundled_library(library_dir: &Path) -> Result<PathBuf, String> {
    Ok(first)
 }

+fn prepare_library_path_for_dylint(library_path: &Path) -> Result<PathBuf, String> {
+    let Some(normalized_filename) = normalize_nightly_library_filename(library_path) else {
+        return Ok(library_path.to_path_buf());
+    };
+
+    let temp_dir = env::temp_dir().join(format!(
+        "argument-comment-lint-{}-{}",
+        std::process::id(),
+        SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .map_err(|err| format!("failed to compute timestamp for temp dir: {err}"))?
+            .as_nanos()
+    ));
+    fs::create_dir_all(&temp_dir).map_err(|err| {
+        format!(
+            "failed to create temporary directory {}: {err}",
+            temp_dir.display()
+        )
+    })?;
+    let normalized_path = temp_dir.join(normalized_filename);
+    fs::copy(library_path, &normalized_path).map_err(|err| {
+        format!(
+            "failed to copy packaged library {} to {}: {err}",
+            library_path.display(),
+            normalized_path.display()
+        )
+    })?;
+    Ok(normalized_path)
+}
+
+fn normalize_nightly_library_filename(library_path: &Path) -> Option<String> {
+    let stem = library_path.file_stem()?.to_string_lossy();
+    let extension = library_path.extension()?.to_string_lossy();
+    let (lib_name, toolchain) = stem.rsplit_once('@')?;
+    let normalized_toolchain = normalize_nightly_toolchain(toolchain)?;
+    Some(format!("{lib_name}@{normalized_toolchain}.{extension}"))
+}
+
+fn normalize_nightly_toolchain(toolchain: &str) -> Option<String> {
+    let parts: Vec<_> = toolchain.split('-').collect();
+    if parts.len() > 4
+        && parts[0] == "nightly"
+        && parts[1].len() == 4
+        && parts[2].len() == 2
+        && parts[3].len() == 2
+        && parts[1..4]
+            .iter()
+            .all(|part| part.chars().all(|ch| ch.is_ascii_digit()))
+    {
+        Some(format!("nightly-{}-{}-{}", parts[1], parts[2], parts[3]))
+    } else {
+        None
+    }
+}
+
 fn exit_code_from_status(code: Option<i32>) -> ExitCode {
    code.and_then(|value| u8::try_from(value).ok())
        .map_or_else(|| ExitCode::from(1), ExitCode::from)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::normalize_nightly_library_filename;
+    use std::path::Path;
+
+    #[test]
+    fn strips_host_triple_from_nightly_filename() {
+        assert_eq!(
+            normalize_nightly_library_filename(Path::new(
+                "libargument_comment_lint@nightly-2025-09-18-aarch64-apple-darwin.dylib"
+            )),
+            Some(String::from(
+                "libargument_comment_lint@nightly-2025-09-18.dylib"
+            ))
+        );
+    }
+
+    #[test]
+    fn leaves_unqualified_nightly_filename_alone() {
+        assert_eq!(
+            normalize_nightly_library_filename(Path::new(
+                "libargument_comment_lint@nightly-2025-09-18.dylib"
+            )),
+            None
+        );
+    }
+}