This is a follow-up to https://github.com/nushell/nushell/pull/8379 and
https://github.com/nushell/nushell/discussions/8502.
This PR makes it so that the new `?` syntax for marking a path member as
optional short-circuits, as voted on in the
[8502](https://github.com/nushell/nushell/discussions/8502) poll.
Previously, `{ foo: 123 }.bar?.baz` would raise an error:
```
> { foo: 123 }.bar?.baz
× Data cannot be accessed with a cell path
╭─[entry #15:1:1]
1 │ { foo: 123 }.bar?.baz
· ─┬─
· ╰── nothing doesn't support cell paths
╰────
```
Here's what was happening:
1. The `bar?` path member access returns `nothing` because there is no field named `bar` on the record
2. The `baz` path member access fails when trying to access a `baz` field on that `nothing` value
After this change, `{ foo: 123 }.bar?.baz` returns `nothing`; the failed `bar?` access immediately returns `nothing` and the `baz` access never runs.
# Description
This adds a new cell path literal syntax for use in any value position,
not just in a context where we expect a cell path.
This can be used to assign to a variable and then later use that
variable as a cell path.
Example:
```
> let cell_path = $.a.b
> {a: {b: 3}} | get $cell_path
3
```
# User-Facing Changes
This adds the syntax `$.a.b` to universally mean the cell path `a.b`,
even in a context that doesn't expect a cell path.
# Tests + Formatting
Don't forget to add tests that cover your changes.
Make sure you've run and fixed any issues with these commands:
- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass
> **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
> ```
# After Submitting
If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.
This is a follow up from https://github.com/nushell/nushell/pull/7540.
Please provide feedback if you have the time!
## Summary
This PR lets you use `?` to indicate that a member in a cell path is
optional and Nushell should return `null` if that member cannot be
accessed.
Unlike the previous PR, `?` is now a _postfix_ modifier for cell path
members. A cell path of `.foo?.bar` means that `foo` is optional and
`bar` is not.
`?` does _not_ suppress all errors; it is intended to help in situations
where data has "holes", i.e. the data types are correct but something is
missing. Type mismatches (like trying to do a string path access on a
date) will still fail.
### Record Examples
```bash
{ foo: 123 }.foo # returns 123
{ foo: 123 }.bar # errors
{ foo: 123 }.bar? # returns null
{ foo: 123 } | get bar # errors
{ foo: 123 } | get bar? # returns null
{ foo: 123 }.bar.baz # errors
{ foo: 123 }.bar?.baz # errors because `baz` is not present on the result from `bar?`
{ foo: 123 }.bar.baz? # errors
{ foo: 123 }.bar?.baz? # returns null
```
### List Examples
```
〉[{foo: 1} {foo: 2} {}].foo
Error: nu:🐚:column_not_found
× Cannot find column
╭─[entry #30:1:1]
1 │ [{foo: 1} {foo: 2} {}].foo
· ─┬ ─┬─
· │ ╰── cannot find column 'foo'
· ╰── value originates here
╰────
〉[{foo: 1} {foo: 2} {}].foo?
╭───┬───╮
│ 0 │ 1 │
│ 1 │ 2 │
│ 2 │ │
╰───┴───╯
〉[{foo: 1} {foo: 2} {}].foo?.2 | describe
nothing
〉[a b c].4? | describe
nothing
〉[{foo: 1} {foo: 2} {}] | where foo? == 1
╭───┬─────╮
│ # │ foo │
├───┼─────┤
│ 0 │ 1 │
╰───┴─────╯
```
# Breaking changes
1. Column names with `?` in them now need to be quoted.
2. The `-i`/`--ignore-errors` flag has been removed from `get` and
`select`
1. After this PR, most `get` error handling can be done with `?` and/or
`try`/`catch`.
4. Cell path accesses like this no longer work without a `?`:
```bash
〉[{a:1 b:2} {a:3}].b.0
2
```
We had some clever code that was able to recognize that since we only
want row `0`, it's OK if other rows are missing column `b`. I removed
that because it's tricky to maintain, and now that query needs to be
written like:
```bash
〉[{a:1 b:2} {a:3}].b?.0
2
```
I think the regression is acceptable for now. I plan to do more work in
the future to enable streaming of cell path accesses, and when that
happens I'll be able to make `.b.0` work again.
# Description
This closes#7498, as well as fixes an issue reported in
https://github.com/nushell/nushell/pull/7002#issuecomment-1368340773
BEFORE:
```
〉[{foo: 'bar'} {}] | get foo
Error: nu:🐚:column_not_found (link)
× Cannot find column
╭─[entry #5:1:1]
1 │ [{foo: 'bar'} {}] | get foo
· ────────┬──────── ─┬─
· │ ╰── value originates here
· ╰── cannot find column 'Empty cell'
╰────
〉[{foo: 'bar'} {}].foo
╭───┬─────╮
│ 0 │ bar │
│ 1 │ │
╰───┴─────╯
```
AFTER:
```
〉[{foo: 'bar'} {}] | get foo
Error: nu:🐚:column_not_found (link)
× Cannot find column
╭─[entry #1:1:1]
1 │ [{foo: 'bar'} {}] | get foo
· ─┬ ─┬─
· │ ╰── cannot find column 'foo'
· ╰── value originates here
╰────
〉[{foo: 'bar'} {}].foo
Error: nu:🐚:column_not_found (link)
× Cannot find column
╭─[entry #3:1:1]
1 │ [{foo: 'bar'} {}].foo
· ─┬ ─┬─
· │ ╰── cannot find column 'foo'
· ╰── value originates here
╰────
```
EDIT: This also changes the semantics of `get`/`select` `-i` somewhat.
I've decided to leave it like this because it works more intuitively
with `default` and `compact`.
BEFORE:
```
〉[{a:1} {b:2} {a:3}] | select -i foo | to nuon
null
```
AFTER:
```
〉[{a:1} {b:2} {a:3}] | select -i foo | to nuon
[[foo]; [null], [null], [null]]
```
# User-Facing Changes
See above. EDIT: the issue with holes in cases like ` [{foo: 'bar'}
{}].foo.0` versus ` [{foo: 'bar'} {}].0.foo` has been resolved.
# Tests + Formatting
Don't forget to add tests that cover your changes.
Make sure you've run and fixed any issues with these commands:
- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass
# After Submitting
If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.
