Nushell 0.83

Nushell, or Nu for short, is a new shell that takes a modern, structured approach to your command line. It works seamlessly with the data from your filesystem, operating system, and a growing number of file formats to make it easy to build powerful command line pipelines.

Today, we're releasing version 0.83 of Nu. This release adds match guards, stronger type checking features, unit testing improvements, flexible variable initializations, and more.

Where to get it

Nu 0.83 is available as pre-built binaries or from crates.io. If you have Rust installed you can install it using cargo install nu.

NOTE: The optional dataframe functionality is available by cargo install nu --features=dataframe.

As part of this release, we also publish a set of optional plugins you can install and use with Nu. To install, use cargo install nu_plugin_<plugin name>.

Themes of this release / New features

Fixes, stabilization and shoutouts

Name	Link	Description
@WindSoilder	9747	Redirection: make `o>`, `e>`, `o+e>`'s target support variables and string interpolation
@kubouch	9679	Fix broken constants in scopes
@rusty-jules	9594	Fix: return all headers with the same name from `http <method>`
@baehyunsol	9582	make the behaviours of `last` and `first` more consistent
@hanjunghyuk	9623	Fix `explore` crashes on {}
@YassineHaouzane	9616	Fix: update engine_state when history.isolation is true (#9268)
@IanManske	9603	Fix `headers` command handling of missing values
@AyushSingh13	9580	fixes `which` showing aliases as built-in nushell commands
@mengsuenyan	9662	fix the command `cp -u src dst`/`mv -u src dst` doesn't work when the…

Changes to commands

Since last release, some commands have changed and some have been created, here is a list of some changes and what they mean:

@amtoine in #9646: which returns the type of the command instead of only whether it is builtin or not and uses more explicit column names
@atahabaki in #9750: str expand now allows empty member in brace expansion, e.g. A{,B,C} would expand to [A, AB, AC]
@fdncred in #9669: keybinding listen gives more information about keys like home and end, namely their kind and state
@NotLebedev in #9453: input listen allows to query for a single key press, e.g. the following will take a 4-char input 1..4 | each { input listen } | where key_type == char | get code | str join
@kubouch in #9687: path commands lose the -c flag; instead, use update to update table columns

Again with this new release, we are continuing refining our set of core commands. As part of this, another set of commands have moved to extra. Thanks to folks who are helping our efforts on the road to 1.0!

Note No command has been removed completely, they have just been moved in the extra feature of Nushell. simply use cargo ... --features extra to reenable them.

Math commands have been moved by @stormasm in #9674, #9657 and #9647 and the following commands have been moved in #9404: fmt, each while, roll, roll down, roll left, roll right, roll up, rotate, update cells, decode hex, encode hex, from url, to html, ansi gradient, ansi linkand format

Language improvements

Since last release, a few changes have happened to the Nu language itself.

Declaration and assignment of variables

Until now, declaration keywords such as let and mut have required the use of parentheses around pipelines to assign the output of a chain of command to a variable. Thanks to @sophiajt in #9658 and #9589, this syntax has been relaxed for let and mut. Let's give some examples!

let filenames = ls | where type == file | get name

and

mut my_var = "hello world" | str length

are now completely valid Nushell code.

Note this new syntax does not work on const and it does not apply to assignment of values to variables, e.g.
$env.FILENAMES = ls | where type == file | get name
is not parsed as valid Nushell.

Another parser improvement has to do with the use of if and match in variable assignment. In #9650, @Windsoilder made the following Nushell snippets possible:

mut a = 3
$a = if 4 == 3 { 10 } else {20}

and

$env.BUILD_EXT = match 3 { 1 => { 'yes!' }, _ => { 'no!' } }

Input / output type checking and annotations (@sophiajt)

Nushell as a language is more strictly typed than other shell languages. However, not everything was type-checked nor possible to annotate and this new release tries to fill this gap a bit more.

Note in the following of this section, the term input / output signature is used. This describes the input of a command and the associated output type of the command for the given input type, e.g. in ls | get 0.name the input type of get is a table and its output type is a string, so we can say that the input / output signature of get here is table -> string.
Please note that input / output signatures always come in pair.

First, #9686 makes the input / output type signatures clearer in the help pages of commands. Then, #9690 and #9680 enable input / output type annotations on custom commands and enforce a strong type checking on the input and output of commands. This means a few things

the input / output of custom commands can be annotated

def sum []: list<int> -> int {
    math sum
}

some type-invalid calls to commands are now parsed as an error, e.g. 123 | get foo gives the following error

Error: nu::parser::input_type_mismatch

  × Command does not support int input.
   ╭─[entry #2:1:1]
 1 │ 123 | get foo
   ·       ─┬─
   ·        ╰── command doesn't support int input
   ╰────

This is still a work in progress, so some commands might have incorrect or missing input / output type annotations 😮 This is expected and we worked and are working on this to fix all incorrect signatures (#9755, #9749, #9707, #9706, #9695, #9683, #9775, #9741, #9742, #9739 and #9778)!

Shoutouts

In between the two releases, @1Kinoti has worked on some nice improvements to the language

match guards have been added to the match command in #9621
table types can now have parameters, just as records and lists can, thanks to #9613
structural subtyping has been improved in #9614 and allow to match structured types regardless of the orders of the fields

Configuration tweaks

Contributions have been made to give a more consistent and sensible default experience in Nushell, both when using the default_config.nu config file or when not having a config, e.g. with nu -n. A better right prompt has been written in #9585 and #9581 and the default configuration has been polished in #9676.

The standard library

The biggest topic in this 0.83 release for the standard library has been the test runner!

Thanks to @Yethal, the test runner of the standard library can now use annotations to decide whether or not to run a command as part of the test suite of a project: #9628, #9622, #9611 and #9406.

For instance, we can now write a module as follows

def add [a: int, b: int] {
    $a + $b
}

#[test]
def addition [] {
    use std assert
    assert equal (add 1 2) 3
}

and std testing run-tests would successfully run the addition test, no need to define tests with test_ in their names!

Thanks to @Hofer-Julian (#9607), the standard library now also comes with a pwd command that tells you were you are in the filesystem.

Breaking changes

PLEASE NOTE: there are some big breaking changes in this release. These include:

Removal of let-env (now use the $env.FOO = "BAR" form instead)
Stricter checking of input/output types
Transitioning of a set of commands to now be available via extra feature rather than default

Full list of breaking changes:

#9574 remove let-env, focus on mutating $env
#9587 disallow blocks as first-class values
#9589 let no longer allows bareword assignment (Eg, let foo = bar where bar is assumed to be a string)
#9582 make the behaviours of last and first more consistent
#9594 Fix: return all headers with the same name from http <method>
#9646 change the output of which to be more explicit
#9404 #9647 #9657 - a number of commands have been moved to extra
#9680 Input output checking
#9613 allow table types to have parameters
#9687 Refactor path commands
#9690 The extern command has split into extern and extern-wrapped, the latter allowing a block to be called when calling an extern