trustpub: Implement extract_workflow_filename() fn

Author: Turbo87

crates/crates_io_trustpub/src/github/mod.rs

@@ -1,3 +1,4 @@
 pub mod validation;
+mod workflows;
 
 pub const GITHUB_ISSUER_URL: &str = "https://token.actions.githubusercontent.com";

crates/crates_io_trustpub/src/github/workflows.rs

@@ -0,0 +1,110 @@
+use std::sync::LazyLock;
+
+/// Extracts the workflow filename from a GitHub workflow reference.
+///
+/// In other words, it turns e.g. `rust-lang/regex/.github/workflows/ci.yml@refs/heads/main`
+/// into `ci.yml`, or `None` if the reference is in an unexpected format.
+#[allow(unused)]
+pub(crate) fn extract_workflow_filename(workflow_ref: &str) -> Option<&str> {
+    static WORKFLOW_REF_RE: LazyLock<regex::Regex> =
+        LazyLock::new(|| regex::Regex::new(r"([^/]+\.(yml|yaml))(@.+)").unwrap());
+
+    WORKFLOW_REF_RE
+        .captures(workflow_ref)
+        .and_then(|caps| caps.get(1))
+        .map(|m| m.as_str())
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_extract_workflow_filename() {
+        let test_cases = [
+            // Well-formed workflow refs, including exceedingly obnoxious ones
+            // with `@` or extra suffixes or `git` refs that look like workflows.
+            (
+                "foo/bar/.github/workflows/basic.yml@refs/heads/main",
+                Some("basic.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/basic.yaml@refs/heads/main",
+                Some("basic.yaml"),
+            ),
+            (
+                "foo/bar/.github/workflows/has-dash.yml@refs/heads/main",
+                Some("has-dash.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/has--dashes.yml@refs/heads/main",
+                Some("has--dashes.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/has--dashes-.yml@refs/heads/main",
+                Some("has--dashes-.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/has.period.yml@refs/heads/main",
+                Some("has.period.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/has..periods.yml@refs/heads/main",
+                Some("has..periods.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/has..periods..yml@refs/heads/main",
+                Some("has..periods..yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/has_underscore.yml@refs/heads/main",
+                Some("has_underscore.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/nested@evil.yml@refs/heads/main",
+                Some("nested@evil.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/nested.yml@evil.yml@refs/heads/main",
+                Some("nested.yml@evil.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/extra@nested.yml@evil.yml@refs/heads/main",
+                Some("extra@nested.yml@evil.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/extra.yml@nested.yml@evil.yml@refs/heads/main",
+                Some("extra.yml@nested.yml@evil.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/basic.yml@refs/heads/misleading@branch.yml",
+                Some("basic.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/basic.yml@refs/heads/bad@branch@twomatches.yml",
+                Some("basic.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/foo.yml.yml@refs/heads/main",
+                Some("foo.yml.yml"),
+            ),
+            (
+                "foo/bar/.github/workflows/foo.yml.foo.yml@refs/heads/main",
+                Some("foo.yml.foo.yml"),
+            ),
+            // Malformed workflow refs.
+            (
+                "foo/bar/.github/workflows/basic.wrongsuffix@refs/heads/main",
+                None,
+            ),
+            ("foo/bar/.github/workflows/@refs/heads/main", None),
+            ("foo/bar/.github/workflows/nosuffix@refs/heads/main", None),
+            ("foo/bar/.github/workflows/.yml@refs/heads/main", None),
+            ("foo/bar/.github/workflows/.yaml@refs/heads/main", None),
+            ("foo/bar/.github/workflows/main.yml", None),
+        ];
+
+        for (input, expected) in test_cases {
+            let result = super::extract_workflow_filename(input);
+            assert_eq!(result, expected, "Input: {input}");
+        }
+    }
+}