Don't try to parse Hy as Python in pydoc.getdoc

NEWS.rst

@@ -24,6 +24,7 @@ New Features
 Bug Fixes
 ------------------------------
 * Tracebacks now point to the correct code in more cases.
+* `help` should no longer crash when objects are missing docstrings.
 
 0.28.0 (released 2024-01-05)
 =============================

hy/compat.py

@@ -43,3 +43,21 @@ def rewriting_unparse(ast_obj):
         return true_unparse(ast_obj)
 
     ast.unparse = rewriting_unparse
+
+
+if True:
+    import pydoc, inspect, re
+    true_getdoc = pydoc.getdoc
+    if not PY3_9:
+        pydoc._getdoc = inspect.getdoc
+    def getdoc(object):
+        """A monkey-patched `pydoc.getdoc` that tries to avoid calling
+        `inspect.getcomments` for an object defined in Hy code, which would try
+        to parse the Hy as Python. The implementation is based on Python
+        3.12.3's `getdoc`."""
+        result = pydoc._getdoc(object) or (
+            None
+            if inspect.getfile(object).endswith('.hy')
+            else inspect.getcomments(object))
+        return result and re.sub('^ *\n', '', result.rstrip()) or ''
+    pydoc.getdoc = getdoc

tests/native_tests/other.hy

@@ -1,7 +1,10 @@
 ;; Tests miscellaneous features of the language not covered elsewhere
 
 (import
+  textwrap [dedent]
   typing [get-type-hints]
+  importlib
+  pydoc
   pytest
   hy.errors [HyLanguageError])
 
@@ -50,3 +53,32 @@
   (setv annotations (get-type-hints AnnotationContainer))
   (assert (= (get annotations "x") int))
   (assert (= (get annotations "z") bool)))
+
+
+(defn test-pydoc [tmp-path monkeypatch]
+  ; https://github.com/hylang/hy/issues/2578
+
+  (monkeypatch.syspath-prepend tmp-path)
+
+  (.write-text (/ tmp-path "pydoc_py.py") (dedent #[[
+      class C1:
+          'C1 docstring'
+      # a comment
+      class C2:
+          pass]]))
+  (importlib.invalidate-caches)
+  (import pydoc-py)
+  (assert (= (pydoc.getdoc pydoc-py.C1) "C1 docstring"))
+  (assert (= (pydoc.getdoc pydoc-py.C2) "# a comment"))
+
+  (.write-text (/ tmp-path "pydoc_hy.hy") (dedent #[[
+    (defclass C1 []
+      "C1 docstring")
+    ; a comment
+    (defclass C2)]]))
+  (importlib.invalidate-caches)
+  (import pydoc-hy)
+  (assert (= (pydoc.getdoc pydoc-hy.C1) "C1 docstring"))
+  (assert (= (pydoc.getdoc pydoc-hy.C2) "")))
+    ; `pydoc` shouldn't try to get a comment from Hy code, since it
+    ; doesn't know how to parse Hy.