issue_comments

Or... I could automatically register multiple copies of the function of different arities!

If I'm going to do something like that though I need to think carefully about how functions that have keyword-only arguments should work: https://peps.python.org/pep-3102/

python def compare(a, b, *ignore, key=None): ... I should think about how these work with db.register_function() anyway, since SQL functions cannot support keyword arguments.

OK with this: ```diff diff --git a/sqlite_utils/cli.py b/sqlite_utils/cli.py index c51b101..93d82a9 100644 --- a/sqlite_utils/cli.py +++ b/sqlite_utils/cli.py @@ -30,6 +30,7 @@ from .utils import ( Format, TypeTracker, ) +from . import recipes

CONTEXT_SETTINGS = dict(help_option_names=["-h", "--help"]) @@ -3029,7 +3030,7 @@ def load_extensions(db, load_extension): def _register_functions(db, functions): # Register any Python functions as SQL functions: sqlite3.enable_callback_tracebacks(True) - globals = {} + globals = {"r": recipes, "recipes": recipes} try: exec(functions, globals) except SyntaxError as ex: @@ -3037,4 +3038,4 @@ def _register_functions(db, functions): # Register all callables in the locals dict: for name, value in globals.items(): if callable(value) and not name.startswith(""): - db.register_function(value, name=name) + db.register_function(value, name=name, ignore_defaults=True) diff --git a/sqlite_utils/db.py b/sqlite_utils/db.py index 27c46b0..1407d23 100644 --- a/sqlite_utils/db.py +++ b/sqlite_utils/db.py @@ -370,6 +370,7 @@ class Database: self, fn: Callable = None, deterministic: bool = False, + ignore_defaults: bool = False, replace: bool = False, name: Optional[str] = None, ): @@ -397,7 +398,10 @@ class Database:

     def register(fn):
         fn_name = name or fn.__name__

• arity = len(inspect.signature(fn).parameters)
• params = inspect.signature(fn).parameters
• if ignore_defaults:
• params = [p for p in params if params[p].default is inspect._empty]
• arity = len(params) if not replace and (fn_name, arity) in self._registered_functions: return fn kwargs = {} I can now do this: % sqlite-utils memory --functions 'parsedate = r.parsedate' 'select parsedate("1st jan")' [{"parsedate(\"1st jan\")": "2022-01-01"}] ```

Here's how to detect defaults in the function signature: ```pycon

import inspect def foo(a, b, c=1, d=2): ... pass ... inspect.signature(foo) <Signature (a, b, c=1, d=2)> inspect.signature(foo).parameters mappingproxy(OrderedDict([('a', <Parameter "a">), ('b', <Parameter "b">), ('c', <Parameter "c=1">), ('d', <Parameter "d=2">)])) inspect.signature(foo).parameters['c'] <Parameter "c=1"> dir(inspect.signature(foo).parameters['c']) ['KEYWORD_ONLY', 'POSITIONAL_ONLY', 'POSITIONAL_OR_KEYWORD', 'VAR_KEYWORD', 'VAR_POSITIONAL', 'class', 'delattr', 'dir', 'doc', 'eq', 'format', 'ge', 'getattribute', 'gt', 'hash', 'init', 'init_subclass', 'le', 'lt', 'module', 'ne', 'new', 'reduce', 'reduce_ex', 'repr', 'setattr', 'setstate', 'sizeof', 'slots', 'str', 'subclasshook', '_annotation', '_default', '_kind', '_name', 'annotation', 'default', 'empty', 'kind', 'name', 'replace'] inspect.signature(foo).parameters['c'].default 1 inspect.signature(foo).parameters['a'].default <class 'inspect._empty'> ```

I could do this: python # Register all callables in the locals dict: for name, value in globals.items(): if callable(value) and not name.startswith("_"): db.register_function(value, name=name, ignore_params_with_defaults=True) Introducing a new ignore_params_with_defaults option.

That would be a breaking change though - existing code that registers functions with default parameters should continue to work unchanged (unless I want to ship sqlite-utils 4.0).

I could teach this code here to only register the function using arguments that don't have default parameters:

https://github.com/simonw/sqlite-utils/blob/d9b9e075f07a20f1137cd2e34ed5d3f1a3db4ad8/sqlite_utils/cli.py#L3037-L3040

Or even this code here:

https://github.com/simonw/sqlite-utils/blob/d9b9e075f07a20f1137cd2e34ed5d3f1a3db4ad8/sqlite_utils/db.py#L398-L418

So you would need to do this instead: sqlite-utils memory 'select parsedate("1st jan")' --functions ' def parsedate(s): return r.parsedate(s) '

It's not quite that simple. I tried applying this patch:

```diff diff --git a/sqlite_utils/cli.py b/sqlite_utils/cli.py index c51b101..33e4d90 100644 --- a/sqlite_utils/cli.py +++ b/sqlite_utils/cli.py @@ -30,6 +30,7 @@ from .utils import ( Format, TypeTracker, ) +from . import recipes

CONTEXT_SETTINGS = dict(help_option_names=["-h", "--help"]) @@ -3029,7 +3030,7 @@ def _load_extensions(db, load_extension): def _register_functions(db, functions): # Register any Python functions as SQL functions: sqlite3.enable_callback_tracebacks(True) - globals = {} + globals = {"r": recipes, "recipes": recipes} try: exec(functions, globals) except SyntaxError as ex: ```

Then got this:

% sqlite-utils memory --functions 'parsedate = r.parsedate' 'select parsedate("1st jan")' Error: wrong number of arguments to function parsedate() % sqlite-utils memory --functions 'parsedate = r.parsedate' 'select parsedate("1st jan", 0, 0, 0)' [{"parsedate(\"1st jan\", 0, 0, 0)": "2022-01-01"}] The problem here is that the parsedate function signature looks like this:

https://github.com/simonw/sqlite-utils/blob/d9b9e075f07a20f1137cd2e34ed5d3f1a3db4ad8/sqlite_utils/recipes.py#L8

But the code that register SQL functions introspects that signature, so creates a SQL function that requires four arguments.

This feature is a tiny bit weird though: the recipe functions are not exposed to SQL by default, they are instead designed to be used with sqlite-utils convert. I guess with --functions support you could do something like this:

sqlite-utils data.db "update mytable set col1 = parsedate(col1)" --functions "parsedate = r.parsedate"

Will also need to update documentation here: https://sqlite-utils.datasette.io/en/stable/cli.html#defining-custom-sql-functions

Here's the implementation for recipes at the moment: https://github.com/simonw/sqlite-utils/blob/5b969273f1244b1bcf3e4dc071cdf17dab35d5f8/sqlite_utils/utils.py#L434-L441

And here's the --functions implementation that doesn't expose them: https://github.com/simonw/sqlite-utils/blob/5b969273f1244b1bcf3e4dc071cdf17dab35d5f8/sqlite_utils/cli.py#L3029-L3040