Re: [PATCH v2] Raise exception if ambiguous name is used in gdb.parameter

[Guinevere Larsen <blarsen@redhat.com>]

On 19/12/2023 17:38, Hannes Domani wrote:
> Currently gdb.parameter doesn't raise an exception if an
> ambiguous name is used, it instead returns the value of the
> last partly matching parameter:
> ```
> (gdb) show print sym
> Ambiguous show print command "sym": symbol, symbol-filename, symbol-loading.
> (gdb) show print symbol-loading
> Printing of symbol loading messages is "full".
> (gdb) py print(gdb.parameter("print sym"))
> full
> ```
>
> It's because lookup_cmd_composition_1 tries to detect
> ambigous names by checking the return value of find_cmd
> for CMD_LIST_AMBIGUOUS, which never happens, since only
> lookup_cmd_1 returns CMD_LIST_AMBIGUOUS.
> Instead the nfound argument contains the number of found
> matches.
>
> By using it instead, and by setting *CMD to the special value
> CMD_LIST_AMBIGUOUS in this case, gdbpy_parameter can now show
> the appropriate error message:
> ```
> (gdb) py print(gdb.parameter("print sym"))
> Traceback (most recent call last):
>    File "<string>", line 1, in <module>
> RuntimeError: Parameter `print sym' is ambiguous.
> Error while executing Python code.
> (gdb) py print(gdb.parameter("print symbol"))
> True
> (gdb) py print(gdb.parameter("print symbol-"))
> Traceback (most recent call last):
>    File "<string>", line 1, in <module>
> RuntimeError: Parameter `print symbol-' is ambiguous.
> Error while executing Python code.
> (gdb) py print(gdb.parameter("print symbol-load"))
> full
> ```
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=14639
> ---
> v2:
> - Small changes in commit message.
> - Use CMD_LIST_AMBIGUOUS in lookup_cmd_composition_1 to mark
>    ambiguous commands, so gdbpy_parameter can show a better
>    error message.
> ---

I've taken a look at this, and it looks good. I think your solution of 
returning CMD_LIST_AMBIGUOUS is better than the original suggestion of 
returning nullptr, and this test doesn't introduce any regressions.

Reviewed-By: Guinevere Larsen <blarsen@redhat.com>

-- 
Cheers,
Guinevere Larsen
She/Her/Hers

>   gdb/cli/cli-decode.c                      | 13 ++++++---
>   gdb/python/python.c                       |  5 +++-
>   gdb/testsuite/gdb.python/py-parameter.exp | 32 +++++++++++++++++++++++
>   3 files changed, 46 insertions(+), 4 deletions(-)
>
> diff --git a/gdb/cli/cli-decode.c b/gdb/cli/cli-decode.c
> index 940cd6a2c8e..db57764578d 100644
> --- a/gdb/cli/cli-decode.c
> +++ b/gdb/cli/cli-decode.c
> @@ -2549,7 +2549,8 @@ deprecated_cmd_warning (const char *text, struct cmd_list_element *list)
>      If TEXT is a subcommand (i.e. one that is preceded by a prefix
>      command) set *PREFIX_CMD.
>   
> -   Set *CMD to point to the command TEXT indicates.
> +   Set *CMD to point to the command TEXT indicates, or to
> +   CMD_LIST_AMBIGUOUS if there are multiple possible matches.
>   
>      If any of *ALIAS, *PREFIX_CMD, or *CMD cannot be determined or do not
>      exist, they are NULL when we return.
> @@ -2589,7 +2590,12 @@ lookup_cmd_composition_1 (const char *text,
>         *cmd = find_cmd (command.c_str (), len, cur_list, 1, &nfound);
>   
>         /* We only handle the case where a single command was found.  */
> -      if (*cmd == CMD_LIST_AMBIGUOUS || *cmd == nullptr)
> +      if (nfound > 1)
> +	{
> +	  *cmd = CMD_LIST_AMBIGUOUS;
> +	  return 0;
> +	}
> +      else if (*cmd == nullptr)
>   	return 0;
>         else
>   	{
> @@ -2623,7 +2629,8 @@ lookup_cmd_composition_1 (const char *text,
>      If TEXT is a subcommand (i.e. one that is preceded by a prefix
>      command) set *PREFIX_CMD.
>   
> -   Set *CMD to point to the command TEXT indicates.
> +   Set *CMD to point to the command TEXT indicates, or to
> +   CMD_LIST_AMBIGUOUS if there are multiple possible matches.
>   
>      If any of *ALIAS, *PREFIX_CMD, or *CMD cannot be determined or do not
>      exist, they are NULL when we return.
> diff --git a/gdb/python/python.c b/gdb/python/python.c
> index 951de82ef06..fa0b1ca6604 100644
> --- a/gdb/python/python.c
> +++ b/gdb/python/python.c
> @@ -559,7 +559,10 @@ gdbpy_parameter (PyObject *self, PyObject *args)
>         GDB_PY_HANDLE_EXCEPTION (ex);
>       }
>   
> -  if (!found)
> +  if (cmd == CMD_LIST_AMBIGUOUS)
> +    return PyErr_Format (PyExc_RuntimeError,
> +			 _("Parameter `%s' is ambiguous."), arg);
> +  else if (!found)
>       return PyErr_Format (PyExc_RuntimeError,
>   			 _("Could not find parameter `%s'."), arg);
>   
> diff --git a/gdb/testsuite/gdb.python/py-parameter.exp b/gdb/testsuite/gdb.python/py-parameter.exp
> index c1f8a80c6b7..828fe84694d 100644
> --- a/gdb/testsuite/gdb.python/py-parameter.exp
> +++ b/gdb/testsuite/gdb.python/py-parameter.exp
> @@ -588,6 +588,37 @@ proc_with_prefix test_language {} {
>       gdb_test_no_output "set lang auto"
>   }
>   
> +proc_with_prefix test_ambiguous_parameter {} {
> +    gdb_test_multiline "create parameter" \
> +	"python" "" \
> +	"class TestAmbiguousParam (gdb.Parameter):" "" \
> +	"   def __init__ (self, name, value):" "" \
> +	"      super (TestAmbiguousParam, self).__init__ (name, gdb.COMMAND_DATA, gdb.PARAM_INTEGER)" "" \
> +	"      self.value = value" "" \
> +	"end"
> +
> +    # Create parameters.
> +    gdb_test "python TestAmbiguousParam('test-ambiguous-value-1', 1)" ""
> +    gdb_test "python TestAmbiguousParam('test-ambiguous-value-2-extra', 2)" ""
> +    gdb_test "python TestAmbiguousParam('test-ambiguous', 3)" ""
> +
> +    # Test unambiguous matches.
> +    gdb_test "python print(gdb.parameter('test-ambiguous-value-1'))" "1"
> +    gdb_test "python print(gdb.parameter('test-ambiguous-value-2-extra'))" "2"
> +    gdb_test "python print(gdb.parameter('test-ambiguous-value-2'))" "2"
> +    gdb_test "python print(gdb.parameter('test-ambiguous'))" "3"
> +
> +    # Test ambiguous names.
> +    gdb_test "python print(gdb.parameter('test-ambiguou'))" \
> +	"Parameter .* is ambiguous.*Error while executing Python code."
> +    gdb_test "python print(gdb.parameter('test-ambiguous-'))" \
> +	"Parameter .* is ambiguous.*Error while executing Python code."
> +    gdb_test "python print(gdb.parameter('test-ambiguous-v'))" \
> +	"Parameter .* is ambiguous.*Error while executing Python code."
> +    gdb_test "python print(gdb.parameter('test-ambiguous-value-1a'))" \
> +	"Could not find parameter.*Error while executing Python code."
> +}
> +
>   test_directories
>   test_data_directory
>   test_boolean_parameter
> @@ -600,5 +631,6 @@ test_gdb_parameter
>   test_integer_parameter
>   test_throwing_parameter
>   test_language
> +test_ambiguous_parameter
>   
>   rename py_param_test_maybe_no_output ""