feat: add support for file_opener option in Rust, similiar to #911 (#957)

This ports the enhancement introduced in
https://github.com/openai/codex/pull/911 (and the fixes in
https://github.com/openai/codex/pull/919) for the TypeScript CLI to the
Rust one.

codex-rs/tui/src/markdown.rs

@@ -1,8 +1,32 @@
+use codex_core::config::Config;
+use codex_core::config::UriBasedFileOpener;
 use ratatui::text::Line;
 use ratatui::text::Span;
+use std::borrow::Cow;
+use std::path::Path;
 
-pub(crate) fn append_markdown(markdown_source: &str, lines: &mut Vec<Line<'static>>) {
-    let markdown = tui_markdown::from_str(markdown_source);
+use crate::citation_regex::CITATION_REGEX;
+
+pub(crate) fn append_markdown(
+    markdown_source: &str,
+    lines: &mut Vec<Line<'static>>,
+    config: &Config,
+) {
+    append_markdown_with_opener_and_cwd(markdown_source, lines, config.file_opener, &config.cwd);
+}
+
+fn append_markdown_with_opener_and_cwd(
+    markdown_source: &str,
+    lines: &mut Vec<Line<'static>>,
+    file_opener: UriBasedFileOpener,
+    cwd: &Path,
+) {
+    // Perform citation rewrite *before* feeding the string to the markdown
+    // renderer. When `file_opener` is absent we bypass the transformation to
+    // avoid unnecessary allocations.
+    let processed_markdown = rewrite_file_citations(markdown_source, file_opener, cwd);
+
+    let markdown = tui_markdown::from_str(&processed_markdown);
 
     // `tui_markdown` returns a `ratatui::text::Text` where every `Line` borrows
     // from the input `message` string. Since the `HistoryCell` stores its lines
@@ -28,3 +52,112 @@ pub(crate) fn append_markdown(markdown_source: &str, lines: &mut Vec<Line<'stati
         lines.push(owned_line);
     }
 }
+
+/// Rewrites file citations in `src` into markdown hyperlinks using the
+/// provided `scheme` (`vscode`, `cursor`, etc.). The resulting URI follows the
+/// format expected by VS Code-compatible file openers:
+///
+/// ```text
+/// <scheme>://file<ABS_PATH>:<LINE>
+/// ```
+fn rewrite_file_citations<'a>(
+    src: &'a str,
+    file_opener: UriBasedFileOpener,
+    cwd: &Path,
+) -> Cow<'a, str> {
+    // Map enum values to the corresponding URI scheme strings.
+    let scheme: &str = match file_opener.get_scheme() {
+        Some(scheme) => scheme,
+        None => return Cow::Borrowed(src),
+    };
+
+    CITATION_REGEX.replace_all(src, |caps: &regex::Captures<'_>| {
+        let file = &caps[1];
+        let start_line = &caps[2];
+
+        // Resolve the path against `cwd` when it is relative.
+        let absolute_path = {
+            let p = Path::new(file);
+            let absolute_path = if p.is_absolute() {
+                path_clean::clean(p)
+            } else {
+                path_clean::clean(cwd.join(p))
+            };
+            // VS Code expects forward slashes even on Windows because URIs use
+            // `/` as the path separator.
+            absolute_path.to_string_lossy().replace('\\', "/")
+        };
+
+        // Render as a normal markdown link so the downstream renderer emits
+        // the hyperlink escape sequence (when supported by the terminal).
+        //
+        // In practice, sometimes multiple citations for the same file, but with a
+        // different line number, are shown sequentially, so we:
+        // - include the line number in the label to disambiguate them
+        // - add a space after the link to make it easier to read
+        format!("[{file}:{start_line}]({scheme}://file{absolute_path}:{start_line}) ")
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+
+    #[test]
+    fn citation_is_rewritten_with_absolute_path() {
+        let markdown = "See 【F:/src/main.rs†L42-L50】 for details.";
+        let cwd = Path::new("/workspace");
+        let result = rewrite_file_citations(markdown, UriBasedFileOpener::VsCode, cwd);
+
+        assert_eq!(
+            "See [/src/main.rs:42](vscode://file/src/main.rs:42)  for details.",
+            result
+        );
+    }
+
+    #[test]
+    fn citation_is_rewritten_with_relative_path() {
+        let markdown = "Refer to 【F:lib/mod.rs†L5】 here.";
+        let cwd = Path::new("/home/user/project");
+        let result = rewrite_file_citations(markdown, UriBasedFileOpener::Windsurf, cwd);
+
+        assert_eq!(
+            "Refer to [lib/mod.rs:5](windsurf://file/home/user/project/lib/mod.rs:5)  here.",
+            result
+        );
+    }
+
+    #[test]
+    fn citation_followed_by_space_so_they_do_not_run_together() {
+        let markdown = "TODOs on lines 【F:src/foo.rs†L24】【F:src/foo.rs†L42】";
+        let cwd = Path::new("/home/user/project");
+        let result = rewrite_file_citations(markdown, UriBasedFileOpener::VsCode, cwd);
+
+        assert_eq!(
+            "TODOs on lines [src/foo.rs:24](vscode://file/home/user/project/src/foo.rs:24) [src/foo.rs:42](vscode://file/home/user/project/src/foo.rs:42) ",
+            result
+        );
+    }
+
+    #[test]
+    fn citation_unchanged_without_file_opener() {
+        let markdown = "Look at 【F:file.rs†L1】.";
+        let cwd = Path::new("/");
+        let unchanged = rewrite_file_citations(markdown, UriBasedFileOpener::VsCode, cwd);
+        // The helper itself always rewrites – this test validates behaviour of
+        // append_markdown when `file_opener` is None.
+        let mut out = Vec::new();
+        append_markdown_with_opener_and_cwd(markdown, &mut out, UriBasedFileOpener::None, cwd);
+        // Convert lines back to string for comparison.
+        let rendered: String = out
+            .iter()
+            .flat_map(|l| l.spans.iter())
+            .map(|s| s.content.clone())
+            .collect::<Vec<_>>()
+            .join("");
+        assert_eq!(markdown, rendered);
+        // Ensure helper rewrites.
+        assert_ne!(markdown, unchanged);
+    }
+}