binutils-gdb/gdb/testsuite/gdb.python/py-completion.exp
Sergio Durigan Junior 6d62641c83 Fix Python completion when using the "complete" command
This patch is related to PR python/16699, and is an improvement over the
patch posted here:

  <https://sourceware.org/ml/gdb-patches/2014-03/msg00301.html>

Keith noticed that, when using the "complete" command on GDB to complete
a Python command, some strange things could happen.  In order to
understand what can go wrong, I need to explain how the Python
completion mechanism works.

When the user requests a completion of a Python command by using TAB,
GDB will first try to determine the right set of "brkchars" that will be
used when doing the completion.  This is done by actually calling the
"complete" method of the Python class.  Then, when we already know the
"brkchars" that will be used, we call the "complete" method again, for
the same values.

If you read the thread mentioned above, you will see that one of the
design decisions was to make the "cmdpy_completer_helper" (which is the
function the does the actual calling of the "complete" method) cache the
first result of the completion, since this result will be used in the
second call, to do the actual completion.

The problem is that the "complete" command does not process the
brkchars, and the current Python completion mechanism (improved by the
patch mentioned above) relies on GDB trying to determine the brkchars,
and then doing the completion itself.  Therefore, when we use the
"complete" command instead of doing a TAB-completion on GDB, there is a
scenario where we can use the invalid cache of a previous Python command
that was completed before.  For example:

  (gdb) A <TAB>
  (gdb) complete B
  B value1
  B value10
  B value2
  B value3
  B value4
  B value5
  B value6
  B value7
  B value8
  B value9
  (gdb) B <TAB>
  comp1   comp2   comp4   comp6   comp8
  comp10  comp3   comp5   comp7   comp9

Here, we see that "complete B " gave a different result than "B <TAB>".
The reason for that is because "A <TAB>" was called before, and its
completion results were "value*", so when GDB tried to "complete B " it
wrongly answered with the results for A.  The problem here is using a
wrong cache (A's cache) for completing B.

We tried to come up with a solution that would preserve the caching
mechanism, but it wasn't really possible.  So I decided to completely
remove the cache, and doing the method calling twice for every
completion.  This is not optimal, but I do not think it will impact
users noticeably.

It is worth mentioning another small issue that I found.  The code was
doing:

  wordobj = PyUnicode_Decode (word, sizeof (word), host_charset (), NULL);

which is totally wrong, because using "sizeof" here will lead to always
the same result.  So I changed this to use "strlen".  The testcase also
catches this problem.

Keith kindly expanded the existing testcase to cover the problem
described above, and everything is passing.

gdb/ChangeLog:
2015-04-08  Sergio Durigan Junior  <sergiodj@redhat.com>

	PR python/16699
	* python/py-cmd.c (cmdpy_completer_helper): Adjust function to not
	use a caching mechanism.  Adjust comments and code to reflect
	that.  Replace 'sizeof' by 'strlen' when fetching 'wordobj'.
	(cmdpy_completer_handle_brkchars): Adjust call to
	cmdpy_completer_helper.  Call Py_XDECREF for 'resultobj'.
	(cmdpy_completer): Likewise.

gdb/testsuite/ChangeLog:
2015-04-08  Keith Seitz  <keiths@redhat.com>

	PR python/16699
	* gdb.python/py-completion.exp: New tests for completion.
	* gdb.python/py-completion.py (CompleteLimit1): New class.
	(CompleteLimit2): Likewise.
	(CompleteLimit3): Likewise.
	(CompleteLimit4): Likewise.
	(CompleteLimit5): Likewise.
	(CompleteLimit6): Likewise.
	(CompleteLimit7): Likewise.
2015-04-08 18:27:10 -04:00

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# Copyright (C) 2014-2015 Free Software Foundation, Inc.
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
set testfile "py-completion"
load_lib gdb-python.exp
gdb_exit
gdb_start
# Skip all tests if Python scripting is not enabled.
if { [skip_python_tests] } { continue }
gdb_test_no_output "source ${srcdir}/${subdir}/${testfile}.py"
# Create a temporary directory
set testdir "[standard_output_file "py-completion-testdir"]/"
set testdir_regex [string_to_regexp $testdir]
set testdir_complete [standard_output_file "py-completion-test"]
file mkdir $testdir
# This one should always pass.
send_gdb "completefileinit ${testdir_complete}\t"
gdb_test_multiple "" "completefileinit completion" {
-re "^completefileinit ${testdir_regex}$" {
pass "completefileinit completion"
}
}
# Just discarding whatever we typed.
set discard 0
gdb_test " " ".*" "discard #[incr discard]"
# This is the problematic one.
send_gdb "completefilemethod ${testdir_complete}\t"
gdb_test_multiple "" "completefilemethod completion" {
-re "^completefilemethod ${testdir_regex} $" {
fail "completefilemethod completion (completed filename as wrong command arg)"
}
-re "^completefilemethod ${testdir_regex}$" {
pass "completefilemethod completion"
}
}
# Discarding again
gdb_test " " ".*" "discard #[incr discard]"
# Another problematic
set completion_regex "[string_to_regexp [standard_output_file "py-completion-t"]]"
send_gdb "completefilecommandcond [standard_output_file "py-completion-t\t"]"
gdb_test_multiple "" "completefilecommandcond completion" {
-re "^completefilecommandcond ${testdir}$" {
fail "completefilecommandcond completion (completed filename instead of command)"
}
-re "^completefilecommandcond ${completion_regex}\007$" {
pass "completefilecommandcond completion"
}
}
# Start gdb over again to clear out current state. This can interfere
# with the expected output of the below tests in a buggy gdb.
gdb_exit
gdb_start
gdb_test_no_output "source ${srcdir}/${subdir}/${testfile}.py"
gdb_test_sequence "complete completel" \
"list all completions of 'complete completel'" {
"completelimit1"
"completelimit2"
"completelimit3"
"completelimit4"
"completelimit5"
"completelimit6"
"completelimit7"
}
# Discarding again
gdb_test " " ".*" "discard #[incr discard]"
gdb_test_sequence "complete completelimit1 c" \
"list all completions of 'complete completelimit1 c'" {
"completelimit1 cl11"
"completelimit1 cl12"
"completelimit1 cl13"
}
# Discarding again
gdb_test " " ".*" "discard #[incr discard]"
# If using readline, we can TAB-complete. This used to trigger a bug
# because the cached result from the completer was being reused for
# a different python command.
if {[readline_is_used]} {
set testname "tab-complete 'completelimit1 c'"
send_gdb "completelimit1 c\t"
gdb_test_multiple "" $testname {
-re "^completelimit1 c\\\x07l1$" {
pass $testname
# Discard the command line
gdb_test " " ".*" "discard #[incr discard]"
}
}
gdb_test_sequence "complete completelimit2 c" \
"list all completions of 'complete completelimit2 c'" {
"completelimit2 cl21"
"completelimit2 cl210"
"completelimit2 cl22"
"completelimit2 cl23"
"completelimit2 cl24"
"completelimit2 cl25"
"completelimit2 cl26"
"completelimit2 cl27"
"completelimit2 cl28"
"completelimit2 cl29"
}
}