Re: [PATCH v3] gdb/testsuite: fix completion tests when using READ1

[Guinevere Larsen <blarsen@redhat.com>]

On 07/11/2023 14:47, Andrew Burgess wrote:
> Guinevere Larsen via Gdb-patches <gdb-patches@sourceware.org> writes:
>
>> The commit a3da2e7e550c4fe79128b5e532dbb90df4d4f418 has introduced
>> regressions when testing using the READ1 mechanism. The reason for that
>> is the new failure path in proc test_gdb_complete_tab_unique, which
>> looks for GDB suggesting more than what the test inputted, but not the
>> correct answer, followed by a white space. Consider the following case:
>>
>> int foo(int bar, int baz);
>>
>> Sending the command "break foo<tab>" to GDB will return
>>
>> break foo(int, int)
>>
>> which easily fits the buffer in normal testing, so everything works, but
>> when reading one character at a time, the test will find the partial
>> "break foo(int, " and assume that there was a mistake, so we get a
>> spurious FAIL.
>>
>> That change was added because we wanted to avoid forcing a completion
>> failure to fail through timeout, which it had to do because there is no
>> way to verify that the output is done, mostly because when I was trying
>> to solve a different problem I kept getting reading errors and testing
>> completion was frustrating.
>>
>> This commit implements a better way to avoid that frustration, by first
>> testing gdb's complete command and only if that passes we will test tab
>> completion. The difference is that when testing with the complete
>> command, we can tell when the output is over when we receive the GDB
>> prompt again, so we don't need to rely on timeouts. With this, the
>> change to test_gdb_complete_tab_unique has been removed as that test
>> will only be run and fail in the very unlikely scenario that tab
>> completion is different than command completion.
>> ---
>>   gdb/testsuite/lib/completion-support.exp | 31 +++++++++++++++---------
>>   1 file changed, 20 insertions(+), 11 deletions(-)
>>
>> diff --git a/gdb/testsuite/lib/completion-support.exp b/gdb/testsuite/lib/completion-support.exp
>> index fdc512838c3..56c0eee8e1d 100644
>> --- a/gdb/testsuite/lib/completion-support.exp
>> +++ b/gdb/testsuite/lib/completion-support.exp
>> @@ -111,15 +111,11 @@ proc test_gdb_complete_tab_unique { input_line complete_line_re append_char_re }
>>   
>>       set test "tab complete \"$input_line\""
>>       send_gdb "$input_line\t"
>> -    set partial_complete [string_to_regexp $input_line]
>>       set res 1
>>       gdb_test_multiple "" "$test" {
>>   	-re "^$complete_line_re$append_char_re$" {
>>   	    pass "$test"
>>   	}
>> -	-re "$partial_complete\[^ \]+ $" {
>> -	    fail "$test"
>> -	}
>>   	timeout {
>>   	    fail "$test (timeout)"
>>   	    set res -1
>> @@ -194,17 +190,21 @@ proc test_gdb_complete_cmd_none { line } {
>>   proc test_gdb_complete_cmd_unique { input_line complete_line_re } {
>>       global gdb_prompt
>>   
>> +    set res 0
>>       set cmd "complete $input_line"
>>       set cmd_re [string_to_regexp $cmd]
>>       set test "cmd complete \"$input_line\""
>>       gdb_test_multiple $cmd $test {
>>   	-re "^$cmd_re\r\n$complete_line_re\r\n$gdb_prompt $" {
>>   	    pass $test
>> +	    set res 1
>>   	}
>>   	-re "$gdb_prompt $" {
>>   	    fail "$test"
>> +	    set res -1
>>   	}
>>       }
>> +    return $res
>>   }
>>   
>>   # Test that completing "CMD_PREFIX + COMPLETION_WORD" with the
>> @@ -263,12 +263,6 @@ proc test_gdb_complete_none { input_line } {
>>   
>>   proc test_gdb_complete_unique_re { input_line complete_line_re {append_char " "} {max_completions 0}} {
>>       set append_char_re [string_to_regexp $append_char]
>> -    if { [readline_is_used] } {
>> -	if { [test_gdb_complete_tab_unique $input_line $complete_line_re \
>> -		  $append_char_re] == -1 } {
>> -	    return -1
>> -	}
>> -    }
>>   
>>       # Trim COMPLETE LINE, for the case we're completing a command with leading
>>       # whitespace.  Leading command whitespace is discarded by GDB.
>> @@ -288,7 +282,22 @@ proc test_gdb_complete_unique_re { input_line complete_line_re {append_char " "}
>>   	    "\r\n$input_line_re $max_completion_reached_msg_re"
>>       }
>>   
>> -    test_gdb_complete_cmd_unique $input_line $expected_output_re
>> +    # First test completion with the command, then with tab.
>> +    # It is done in this order because cmd_complete knows when the output
>> +    # from GDB is over, so it can fail without requiring a timeout, which
>> +    # speeds up testing if necessary.
>> +
>> +    if { [test_gdb_complete_cmd_unique $input_line\
>> +		$expected_output_re] == -1 } {
>> +	return -1
>> +    }
> This doesn't seem right.  Or at least, it's not really inline with how
> the return value from this proc is used.
>
> Check out `test_complete_prefix_range_re`.  In here you can see that a
> return value of -1 is used to indicate that a test in
> test_gdb_complete_unique_re timedout, while here you're using it to
> indicate general failure.
That's fair, I should have looked around before deciding.
>
> I would suggest that `test_gdb_complete_cmd_unique` should simply return
> true/false to indicate if the test passed or failed (for any reason).
> Then in `test_gdb_complete_unique_re` you can just:
>
>      if { ![test_gdb_complete_cmd_unique $input_line\
> 		$expected_output_re] } {
> 	return 0
>      }
>
> The users of `test_gdb_complete_unique_re` can then continue to see -1
> as the timeout indicator.
>
> Of course, you could have test_gdb_complete_cmd_unique return -1 on
> timeout, but I suspect a timeout here is much less likely, so maybe the
> extra complexity of catching this case isn't worth the effort?  I don't
> think I'd bother, but you might feel different.
I think its easy enough to implement the timeout warning, and this way 
its there if anyone wants to use it. I'll do this on v4

-- 
Cheers,
Guinevere Larsen
She/Her/Hers

>
> Thanks,
> Andrew
>
>
>
>
>
>
>> +
>> +    if { [readline_is_used] } {
>> +	if { [test_gdb_complete_tab_unique $input_line $complete_line_re \
>> +		  $append_char_re] == -1 } {
>> +	    return -1
>> +	}
>> +    }
>>       return 1
>>   }
>>   
>> -- 
>> 2.41.0