diff mbox series

[PATCHv2] gdb/python: handle completion returning a non-sequence

Message ID 521486ffacc94e0139bf63886c873fc7c142cbc2.1700480026.git.aburgess@redhat.com
State New
Headers
Series [PATCHv2] gdb/python: handle completion returning a non-sequence |

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Commit Message

Andrew Burgess Nov. 20, 2023, 11:40 a.m. UTC 
  Thanks for the feedback.

In V2:

  - Instead of calling 'PyErr_Clear ();' to ignore the error, I'm now
    calling 'PySequence_Check (resultobj.get ())' to specifically
    ignore non-sequence like things.  I think this is a better choice,
    and should have done this in V1,

  - I'm no longer ignoring the error.  The Python completion API
    already ignores many errors/exceptions, so addressing Tom's
    feedback would involve a bigger change, which can come later,

  - As I no longer want to take a position on ignoring vs announcing
    errors, I am no longer adding a test for what happens if the
    completion code raises an exception, as a consequence, I'm not
    going to change the docs as Paul suggested.  If I change the docs
    to explicitly state that exceptions are ignored and mean no
    completions, then this is counter to Tom's feedback that
    exceptions should be displayed.  As both of these issues are not
    the main focus of this patch, I'm just going to ignore them for
    now,

  - Commit message is updated to reflect narrower focus of the patch.
    

Thanks,
Andrew

---

GDB's Python API documentation for gdb.Command.complete() says:

  The 'complete' method can return several values:
     * If the return value is a sequence, the contents of the
       sequence are used as the completions.  It is up to 'complete'
       to ensure that the contents actually do complete the word.  A
       zero-length sequence is allowed, it means that there were no
       completions available.  Only string elements of the sequence
       are used; other elements in the sequence are ignored.

     * If the return value is one of the 'COMPLETE_' constants
       defined below, then the corresponding GDB-internal completion
       function is invoked, and its result is used.

     * All other results are treated as though there were no
       available completions.

So, returning a non-sequence, and non-integer from a complete method
should be fine; it should just be treated as though there are no
completions.

However, if I write a complete method that returns None, I see this
behaviour:

  (gdb) complete completefilenone x
  Python Exception <class 'TypeError'>: 'NoneType' object is not iterable
  warning: internal error: Unhandled Python exception
  (gdb)

Which is caused because we currently assume that anything that is not
an integer must be iterable, and we call PyObject_GetIter on it.  When
this call fails a Python exception is set, but instead of
clearing (and therefore ignoring) this exception as we do everywhere
else in the Python completion code, we instead just return with the
exception set.

In this commit I add a PySequence_Check call.  If this call returns
false (and we've already checked the integer case) then we can assume
there are no completion results.

I've added a test which checks returning a non-sequence.
---
 gdb/python/py-cmd.c                        |  2 +-
 gdb/testsuite/gdb.python/py-completion.exp |  5 +++++
 gdb/testsuite/gdb.python/py-completion.py  | 12 ++++++++++++
 3 files changed, 18 insertions(+), 1 deletion(-)


base-commit: 70fd94b244573225cb04ae41101d495def78b9e6

Comments

Andrew Burgess Nov. 27, 2023, 3:46 p.m. UTC | #1 
Tom Tromey <tom@tromey.com> writes:

>>>>>> "Andrew" == Andrew Burgess <aburgess@redhat.com> writes:
>
> Thanks for doing this.
>
> Andrew>   - I'm no longer ignoring the error.  The Python completion API
> Andrew>     already ignores many errors/exceptions, so addressing Tom's
> Andrew>     feedback would involve a bigger change, which can come later,
>
> It even does so incorrectly :(
> cmdpy_completer_helper does:
>
>   gdbpy_ref<> textobj (PyUnicode_Decode (text, strlen (text), host_charset (),
> 					 NULL));
>   if (textobj == NULL)
>     error (_("Could not convert argument to Python string."));
>
> ...this leaves the Python error set.
>
> There's at least one other instance of this in the function.
>
> Similarly in cmdpy_completer:
>
>       gdbpy_ref<> iter (PyObject_GetIter (resultobj.get ()));
>
>       if (iter == NULL)
> 	return;
>
> If this fails, the error remains set here as well.
>
> Anyway your patch itself seems fine.
> Approved-By: Tom Tromey <tom@tromey.com>

I pushed this patch.  I'll take a look at improving the error handling
in this area.

Thanks,
Andrew
diff mbox series

Patch

diff --git a/gdb/python/py-cmd.c b/gdb/python/py-cmd.c
index 20a384d6907..d3845fc7509 100644
--- a/gdb/python/py-cmd.c
+++ b/gdb/python/py-cmd.c
@@ -290,7 +290,7 @@  cmdpy_completer (struct cmd_list_element *command,
       else if (value >= 0 && value < (long) N_COMPLETERS)
 	completers[value].completer (command, tracker, text, word);
     }
-  else
+  else if (PySequence_Check (resultobj.get ()))
     {
       gdbpy_ref<> iter (PyObject_GetIter (resultobj.get ()));
 
diff --git a/gdb/testsuite/gdb.python/py-completion.exp b/gdb/testsuite/gdb.python/py-completion.exp
index 23f981e944a..89843c96f1f 100644
--- a/gdb/testsuite/gdb.python/py-completion.exp
+++ b/gdb/testsuite/gdb.python/py-completion.exp
@@ -46,6 +46,11 @@  if { [readline_is_used] && ![is_remote host] } {
     # Just discarding whatever we typed.
     gdb_test " " ".*" "discard #[incr discard]"
 
+    # This should offer no suggestions - the complete() methods
+    # returns something that is neither an integer, or a sequence.
+    gdb_test_no_output "complete completefilenone ${testdir_complete}" \
+	"no suggestions given"
+
     # This is the problematic one.
     send_gdb "completefilemethod ${testdir_complete}\t"
     gdb_test_multiple "" "completefilemethod completion" {
diff --git a/gdb/testsuite/gdb.python/py-completion.py b/gdb/testsuite/gdb.python/py-completion.py
index abec06921c0..61b6beffa25 100644
--- a/gdb/testsuite/gdb.python/py-completion.py
+++ b/gdb/testsuite/gdb.python/py-completion.py
@@ -28,6 +28,17 @@  class CompleteFileInit(gdb.Command):
         raise gdb.GdbError("not implemented")
 
 
+class CompleteFileNone(gdb.Command):
+    def __init__(self):
+        gdb.Command.__init__(self, "completefilenone", gdb.COMMAND_USER)
+
+    def invoke(self, argument, from_tty):
+        raise gdb.GdbError("not implemented")
+
+    def complete(self, text, word):
+        return None
+
+
 class CompleteFileMethod(gdb.Command):
     def __init__(self):
         gdb.Command.__init__(self, "completefilemethod", gdb.COMMAND_USER)
@@ -203,6 +214,7 @@  class CompleteLimit7(gdb.Command):
 
 
 CompleteFileInit()
+CompleteFileNone()
 CompleteFileMethod()
 CompleteFileCommandCond()
 CompleteLimit1()