# Description
There are times where explicitly specifying a schema for a dataframe is
needed such as:
- Opening CSV and JSON lines files and needing provide more information
to polars to keep it from failing or in a desire to override default
type conversion
- When converting a nushell value to a dataframe and wanting to override
the default conversion behaviors.
This pull requests provides:
- A flag to allow specifying a schema when using dfr into-df
- A flag to allow specifying a schema when using dfr open that works for
CSV and JSON types
- A new command `dfr schema` which displays schema information and will
allow display support schema dtypes
Schema is specified creating a record that has the key value and the
dtype. Examples usages:
```
{a:1, b:{a:2}} | dfr into-df -s {a: u8, b: {a: i32}} | dfr schema
{a: 1, b: {a: [1 2 3]}, c: [a b c]} | dfr into-df -s {a: u8, b: {a: list<u64>}, c: list<str>} | dfr schema
dfr open -s {pid: i32, ppid: i32, name: str, status: str, cpu: f64, mem: i64, virtual: i64} /tmp/ps.jsonl | dfr schema
```
Supported dtypes:
null
bool
u8
u16
u32
u64
i8
i16
i32
i64
f32
f64
str
binary
date
datetime[time_unit: (ms, us, ns) timezone (optional)]
duration[time_unit: (ms, us, ns)]
time
object
unknown
list[dtype]
structs are also supported but are specified via another record:
{a: u8, b: {d: str}}
Another feature with the dfr schema command is that it returns the data
back in a format that can be passed to provide a valid schema that can
be passed in as schema argument:
<img width="638" alt="Screenshot 2024-01-29 at 10 23 58"
src="https://github.com/nushell/nushell/assets/56345/b49c3bff-5cda-4c86-975a-dfd91d991373">
---------
Co-authored-by: Jack Wright <jack.wright@disqo.com>
# Description
This PR does a few things to help improve type hovers and, in the
process, fixes a few outstanding issues in the type system. Here's a
list of the changes:
* `for` now will try to infer the type of the iteration variable based
on the expression it's given. This fixes things like `for x in [1, 2, 3]
{ }` where `x` now properly gets the int type.
* Removed old input/output type fields from the signature, focuses on
the vec of signatures. Updated a bunch of dataframe commands that hadn't
moved over. This helps tie things together a bit better
* Fixed inference of types from subexpressions to use the last
expression in the block
* Fixed handling of explicit types in `let` and `mut` calls, so we now
respect that as the authoritative type
I also tried to add `def` input/output type inference, but unfortunately
we only know the predecl types universally, which means we won't have
enough information to properly know what the types of the custom
commands are.
# User-Facing Changes
Script typechecking will get tighter in some cases
Hovers should be more accurate in some cases that previously resorted to
any.
# Tests + Formatting
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you're using the standard code style
- `cargo test --workspace` to check that all tests pass
- `cargo run -- crates/nu-std/tests/run.nu` to run the tests for the
standard library
> **Note**
> from `nushell` you can also use the `toolkit` as follows
> ```bash
> use toolkit.nu # or use an `env_change` hook to activate it
automatically
> toolkit check pr
> ```
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# After Submitting
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---------
Co-authored-by: Darren Schroeder <343840+fdncred@users.noreply.github.com>
All of the dataframe commands ported over with no issues...
### 11 tests are commented out (for now)
So 100 of the original 111 tests are passing with only 11 tests being
ignored for now..
As per our conversation in the core team meeting on Wednesday
I took @jntrnr suggestion and just commented out the tests dealing
with
[IntoDatetime](https://github.com/nushell/nushell/blob/main/crates/nu-command/src/conversions/into/mod.rs)
Later on we can move this functionality out of nu-command if we decide
it makes sense...
### The following tests were ignored...
```rust
modified: crates/nu-cmd-dataframe/src/dataframe/series/date/get_day.rs
modified: crates/nu-cmd-dataframe/src/dataframe/series/date/get_hour.rs
modified: crates/nu-cmd-dataframe/src/dataframe/series/date/get_minute.rs
modified: crates/nu-cmd-dataframe/src/dataframe/series/date/get_month.rs
modified: crates/nu-cmd-dataframe/src/dataframe/series/date/get_nanosecond.rs
modified: crates/nu-cmd-dataframe/src/dataframe/series/date/get_ordinal.rs
modified: crates/nu-cmd-dataframe/src/dataframe/series/date/get_second.rs
modified: crates/nu-cmd-dataframe/src/dataframe/series/date/get_week.rs
modified: crates/nu-cmd-dataframe/src/dataframe/series/date/get_weekday.rs
modified: crates/nu-cmd-dataframe/src/dataframe/series/date/get_year.rs
modified: crates/nu-cmd-dataframe/src/dataframe/series/string/strftime.rs
```
