Fix less mouse pager fallback handling

src/rp/pager.py

@@ -1,53 +1,81 @@
-"""Custom pager with mouse scroll support."""
+"""Less-based pager integration with mouse support and fallback."""
 
 from __future__ import annotations
 
+import re
+import signal
 import shutil
 import subprocess
 
 from rich.pager import Pager, SystemPager
 
 
-def _is_mouse_capable_less() -> bool:
-    """Check whether the system has a usable ``less`` executable.
+def _mouse_capable_less() -> str | None:
+    """Return a ``less`` path that likely supports ``--mouse``.
+
+    Mouse support was added in ``less`` 543. This probe is best-effort: it
+    checks that ``less`` exists, asks for its version string, and extracts the
+    version number from the leading ``less <version>`` banner. Any unexpected
+    output is treated as unsupported so the caller can fall back safely.
 
     Returns:
-        True if ``less`` is installed and responds to ``--version``.
+        The resolved ``less`` executable path when it appears mouse-capable,
+        otherwise ``None``.
     """
     less = shutil.which("less")
     if less is None:
-        return False
+        return None
+
     try:
         result = subprocess.run(
             [less, "--version"], capture_output=True, text=True, timeout=5
         )
-        version_str = result.stdout or result.stderr or ""
-        return "GNU" in version_str or "less" in version_str.lower()
     except (subprocess.TimeoutExpired, OSError):
-        return False
+        return None
+
+    version_str = result.stdout or result.stderr or ""
+    match = re.search(r"\bless\s+(\d+)\b", version_str, re.IGNORECASE)
+    if match is None:
+        return None
+
+    if int(match.group(1)) < 543:
+        return None
+
+    return less
 
 
 class MousePager(Pager):
-    """Pager that prefers ``less --mouse`` and falls back to the system pager."""
+    """Pager that prefers ``less -R --mouse`` for mouse scrolling.
+
+    ``less`` is the prerequisite for mouse-enabled paging in this project. If
+    ``less`` is missing, too old, cannot be launched, or exits with a non-zero
+    status, we fall back to Rich's ``SystemPager``. A user interrupt does not
+    trigger a second pager session.
+    """
 
     def show(self, content: str) -> None:
-        """Display content with mouse-scroll support when available.
-
-        Uses ``less --mouse`` when available; otherwise falls back to the system
-        pager.
+        """Display rendered content in ``less -R --mouse`` when possible.
 
         Args:
-            content: Content to display in pager.
+            content: Fully rendered text from Rich.
         """
-        if _is_mouse_capable_less():
-            try:
-                subprocess.run(
-                    ["less", "-R", "--mouse"],
-                    input=content,
-                    text=True,
-                    check=True,
-                )
-                return
-            except (subprocess.CalledProcessError, FileNotFoundError):
-                pass
-        SystemPager().show(content)
+        less = _mouse_capable_less()
+        if less is None:
+            SystemPager().show(content)
+            return
+
+        try:
+            result = subprocess.run(
+                [less, "-R", "--mouse"],
+                input=content,
+                text=True,
+            )
+        except OSError:
+            SystemPager().show(content)
+            return
+
+        if result.returncode in (-signal.SIGINT, 128 + signal.SIGINT):
+            return
+
+        if result.returncode != 0:
+            SystemPager().show(content)