alamb commented on code in PR #14513:
URL: https://github.com/apache/datafusion/pull/14513#discussion_r1943025816
##########
datafusion/functions/src/utils.rs:
##########
@@ -18,10 +18,27 @@
use arrow::array::ArrayRef;
use arrow::datatypes::DataType;
-use datafusion_common::{Result, ScalarValue};
+use datafusion_common::{exec_datafusion_err, Result, ScalarValue};
use datafusion_expr::function::Hint;
use datafusion_expr::ColumnarValue;
+/// Converts a collection of function arguments into an fixed-size array of
length N
+/// producing a reasonable error message in case of unexpected number of
arguments.
Review Comment:
This is very cool
I though it was so cool I tried to write an example:
```suggestion
/// producing a reasonable error message in case of unexpected number of
arguments.
///
/// # Example
/// ```
/// # use datafusion_common::ScalarValue;
/// # use datafusion_common::Result;
/// # use datafusion_expr_common::columnar_value::ColumnarValue;
/// fn my_function(args: &[ColumnarValue]) -> Result<()> {
/// // function expects 2 args, so create a 2-element array
/// let [arg1, arg2] = take_function_args("my_function", args)?;
/// // ... do stuff..
/// Ok(())
/// }
///
/// // Calling the function with 1 argument produces an error:
/// let ten = ColumnarValue::from(ScalarValue::from(10i32));
/// let twenty = ColumnarValue::from(ScalarValue::from(20i32));
/// let args = vec![ten.clone()];
/// let err = my_function(&args).unwrap_err();
/// assert_eq!(err.to_string(), "my_function function requires 2 arguments,
got 1");
/// // Calling the function with 2 arguments works great
/// let args = vec![ten, twenty];
/// my_function(&args).unwrap();
/// ```
```
However, when I did I found this function is not exported publically
```
error[E0425]: cannot find function `take_function_args` in this scope
--> datafusion/functions/src/utils.rs:35:22
|
8 | let [arg1, arg2] = take_function_args("my_function", args)?;
| ^^^^^^^^^^^^^^^^^^ not found in this scope
```
I think this is because utils isn't `pub` exported:
https://github.com/apache/datafusion/blob/ddee4717af08e1cbeddf32f2872c3b6c8d378618/datafusion/functions/src/lib.rs#L141-L140
I suggest we publically export `util` and this method too
Can of course be done in a follow on PR
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