Re: [PATCH v4] gdb/testsuite: fix completion tests when using READ1

[Andrew Burgess <aburgess@redhat.com>]

Guinevere Larsen <blarsen@redhat.com> 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 | 32 ++++++++++++++++--------
>  1 file changed, 21 insertions(+), 11 deletions(-)
>
> diff --git a/gdb/testsuite/lib/completion-support.exp b/gdb/testsuite/lib/completion-support.exp
> index fdc512838c3..cc34ef51e22 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
> @@ -190,21 +186,26 @@ proc test_gdb_complete_cmd_none { line } {
>  
>  # Test that completing LINE with the complete command completes to
>  # COMPLETE_LINE_RE.
> +# Returns 1 if the test passed, 0 if it failed, -1 if it timed out.
>  
>  proc test_gdb_complete_cmd_unique { input_line complete_line_re } {
>      global gdb_prompt
>  
> +    set res -1
>      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 0
>  	}

If you want to return -1 for timeout, then I would follow the pattern of
how test_gdb_complete_tab_unique does it.  Inside the gdb_test_multiple,
add a new block:

  timeout {
    fail "$test (timeout)"
    set res -1
  }

Then you can initialise 'res' to 0 instead of -1, delete the 'set res 0'
for the existing fail case, and now, if any of the additional failure
cases that are added by calling gdb_test_multiple trigger, you'll get a
return value of 0.  For the one passing case you'll get 1, and for the
one timeout case you'll get -1.

>      }
> +    return $res
>  }
>  
>  # Test that completing "CMD_PREFIX + COMPLETION_WORD" with the
> @@ -263,12 +264,6 @@ 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 \
> -		  $append_char_re] == -1 } {
> -	    return -1
> -	}
> -    }
>  
>      # Trim COMPLETE LINE, for the case we're completing a command with leading
>      # whitespace.  Leading command whitespace is discarded by GDB.
> @@ -288,7 +283,22 @@ proc test_gdb_complete_unique_re { input_line complete_line_re {append_char " "}
>  	    "\r\n$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.
> +
> +    set test_result [test_gdb_complete_cmd_unique $input_line\
> +		$expected_output_re]
> +    if { $test_result != 1 } {
> +	return $test_result
> +    }
> +
> +    if { [readline_is_used] } {
> +	set test_result [test_gdb_complete_tab_unique $input_line \
> +		$complete_line_re $append_char_re]
> +	}

This seems wrong.  You probably mean:

    if { [readline_is_used] } {
	if { [test_gdb_complete_tab_unique $input_line \
		  $complete_line_re $append_char_re] == -1 } {
	    return -1
	}
    }

Otherwise, if test_gdb_complete_tab_unique times out -- the only timeout
we really care about -- you'll not return -1.

Thanks,
Andrew

> +    }
>      return 1
>  }
>  
> -- 
> 2.41.0