Prior to this PR, the less/greater than operators (`<`, `>`, `<=`, `>=`)
would throw an error if either side was null. After this PR, these
operators return null if either side (or both) is null.
### Examples
```bash
1 < 3 # true
1 < null # null
null < 3 # null
null < null # null
```
### Motivation
JT [asked the C#
folks](https://discord.com/channels/601130461678272522/615329862395101194/1086137515053957140)
and this is apparently the approach they would choose for comparison
operators if they could start from scratch.
This PR makes `where` more convenient to use on jagged/missing data. For
example, we can now filter on columns that may not be present in every
row:
```
> [{foo: 123} {}] | where foo? > 10
╭───┬─────╮
│ # │ foo │
├───┼─────┤
│ 0 │ 123 │
╰───┴─────╯
```
# Description
Adds improved errors for when a user uses a bashism that nu doesn't
support.
fixes#7237
Examples:
```
Error: nu::parser::shell_andand (link)
× The '&&' operator is not supported in Nushell
╭─[entry #1:1:1]
1 │ ls && ls
· ─┬
· ╰── instead of '&&', use ';' or 'and'
╰────
help: use ';' instead of the shell '&&', or 'and' instead of the boolean '&&'
```
```
Error: nu::parser::shell_oror (link)
× The '||' operator is not supported in Nushell
╭─[entry #8:1:1]
1 │ ls || ls
· ─┬
· ╰── instead of '||', use 'try' or 'or'
╰────
help: use 'try' instead of the shell '||', or 'or' instead of the boolean '||'
```
```
Error: nu::parser::shell_err (link)
× The '2>' shell operation is 'err>' in Nushell.
╭─[entry #9:1:1]
1 │ foo 2> bar.txt
· ─┬
· ╰── use 'err>' instead of '2>' in Nushell
╰────
```
```
Error: nu::parser::shell_outerr (link)
× The '2>&1' shell operation is 'out+err>' in Nushell.
╭─[entry #10:1:1]
1 │ foo 2>&1 bar.txt
· ──┬─
· ╰── use 'out+err>' instead of '2>&1' in Nushell
╰────
help: Nushell redirection will write all of stdout before stderr.
```
# User-Facing Changes
**BREAKING CHANGES**
This removes the `&&` and `||` operators. We previously supported by
`&&`/`and` and `||`/`or`. With this change, only `and` and `or` are
valid boolean operators.
# 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.
We already have the binary `bit-xor` and the shortcircuiting logical
`or`(`||`) and `and`(`&&`).
This introduces `xor` as a compact form for both brevity and clarity.
You can express the operation through `not`/`and`/`or` with a slight
risk of introducing bugs through typos.
Operator precedence
`and` > `xor` > `or`
Added logic and precedence tests.