argparse: Use the current function name by default

This makes the `--name` option usually unnecessary.

See #5835.

CHANGELOG.md

@@ -26,6 +26,7 @@
 - `count` now also counts lines fed on stdin (#5744).
 - `printf` prints what it can when input hasn't been fully converted to a number, but still prints an error (#5532).
 - `complete -C foo` now works instead of erroring out and requiring `complete -Cfoo`.
+- `argparse` now defaults to showing the current function name (instead of `argparse`) in its errors, making `--name` often superfluous (#5835).
 
 ### Interactive improvements
 - Major improvements in performance and functionality to the 'sorin' sample prompt (#5411).

sphinx_doc_src/cmds/argparse.rst

@@ -25,9 +25,9 @@ Options
 
 The following ``argparse`` options are available. They must appear before all OPTION_SPECs:
 
-- ``-n`` or ``--name`` is the command name to insert into any error messages. If you don't provide this value ``argparse`` will be used.
+- ``-n`` or ``--name`` is the command name for use in error messages. By default the current function name will be used, or `argparse` if run outside of a function.
 
-- ``-x`` or ``--exclusive`` should be followed by a comma separated list of short of long options that are mutually exclusive. You can use this option more than once to define multiple sets of mutually exclusive options.
+- ``-x`` or ``--exclusive`` should be followed by a comma separated list of short or long options that are mutually exclusive. You can use this more than once to define multiple sets of mutually exclusive options.
 
 - ``-N`` or ``--min-args`` is followed by an integer that defines the minimum number of acceptable non-option arguments. The default is zero.
 

src/builtin_argparse.cpp

@@ -49,7 +49,7 @@ struct argparse_cmd_opts_t {
     size_t min_args = 0;
     size_t max_args = SIZE_MAX;
     wchar_t implicit_int_flag = L'\0';
-    wcstring name = L"argparse";
+    wcstring name = L"";
     wcstring_list_t raw_exclusive_flags;
     wcstring_list_t argv;
     std::unordered_map<wchar_t, option_spec_ref_t> options;
@@ -405,6 +405,15 @@ static int parse_cmd_opts(argparse_cmd_opts_t &opts, int *optind,  //!OCLINT(hig
         return STATUS_INVALID_ARGS;
     }
 
+    if (opts.name.empty()) {
+        // If no name has been given, we default to the function name.
+        // If any error happens, the backtrace will show which argparse it was.
+        const wchar_t *fn = parser.get_function_name(1);
+
+        if (!fn) fn = L"argparse";
+        opts.name = fn;
+    }
+
     *optind = w.woptind;
     return collect_option_specs(opts, optind, argc, argv, streams);
 }

tests/argparse.err

@@ -104,3 +104,11 @@ argparse: Value 'a1' for flag 'm' is not an integer
 # Explicit int flag validation
 argparse: Value '2' for flag 'm' greater than max allowed of '1'
 argparse: Value '-1' for flag 'max' less than min allowed of '0'
+
+####################
+# Errors use function name by default
+notargparse: Unknown option '--banana'
+Standard input (line 353): 
+    argparse a/alpha -- --banana
+    ^
+in function 'notargparse'

tests/argparse.in

@@ -171,3 +171,11 @@ argparse 'm/max=!_validate_int --min 0 --max 1' -- argle --max=0 bargle
 or echo unexpected argparse return status $status >&2
 argparse 'm/max=!_validate_int --min 0 --max 1' -- argle --max=1 bargle
 or echo unexpected argparse return status $status >&2
+
+logmsg Errors use function name by default
+function notargparse
+    argparse a/alpha -- --banana
+end
+notargparse
+
+true

tests/argparse.out

@@ -129,3 +129,6 @@ expected argparse return status 57
 
 ####################
 # Explicit int flag validation
+
+####################
+# Errors use function name by default