21b3eeed99
<!-- if this PR closes one or more issues, you can automatically link the PR with them by using one of the [*linking keywords*](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue#linking-a-pull-request-to-an-issue-using-a-keyword), e.g. - this PR should close #xxxx - fixes #xxxx you can also mention related issues, PRs or discussions! --> Finishes implementing https://github.com/nushell/nushell/issues/10598, which asks for a spread operator in lists, in records, and when calling commands. # Description <!-- Thank you for improving Nushell. Please, check our [contributing guide](../CONTRIBUTING.md) and talk to the core team before making major changes. Description of your pull request goes here. **Provide examples and/or screenshots** if your changes affect the user experience. --> This PR will allow spreading arguments to commands (both internal and external). It will also deprecate spreading arguments automatically when passing to external commands. # User-Facing Changes <!-- List of all changes that impact the user experience here. This helps us keep track of breaking changes. --> - Users will be able to use `...` to spread arguments to custom/builtin commands that have rest parameters or allow unknown arguments, or to any external command - If a custom command doesn't have a rest parameter and it doesn't allow unknown arguments either, the spread operator will not be allowed - Passing lists to external commands without `...` will work for now but will cause a deprecation warning saying that it'll stop working in 0.91 (is 2 versions enough time?) Here's a function to help with demonstrating some behavior: ```nushell > def foo [ a, b, c?, d?, ...rest ] { [$a $b $c $d $rest] | to nuon } ``` You can pass a list of arguments to fill in the `rest` parameter using `...`: ```nushell > foo 1 2 3 4 ...[5 6] [1, 2, 3, 4, [5, 6]] ``` If you don't use `...`, the list `[5 6]` will be treated as a single argument: ```nushell > foo 1 2 3 4 [5 6] # Note the double [[]] [1, 2, 3, 4, [[5, 6]]] ``` You can omit optional parameters before the spread arguments: ```nushell > foo 1 2 3 ...[4 5] # d is omitted here [1, 2, 3, null, [4, 5]] ``` If you have multiple lists, you can spread them all: ```nushell > foo 1 2 3 ...[4 5] 6 7 ...[8] ...[] [1, 2, 3, null, [4, 5, 6, 7, 8]] ``` Here's the kind of error you get when you try to spread arguments to a command with no rest parameter:  And this is the warning you get when you pass a list to an external now (without `...`):  # 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` to check that you're using the standard code style - `cargo test --workspace` to check that all tests pass (on Windows make sure to [enable developer mode](https://learn.microsoft.com/en-us/windows/apps/get-started/developer-mode-features-and-debugging)) - `cargo run -- -c "use std testing; testing run-tests --path crates/nu-std"` 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 > ``` --> Added tests to cover the following cases: - Spreading arguments to a command that doesn't have a rest parameter (unexpected spread argument error) - Spreading arguments to a command that doesn't have a rest parameter *but* there's also a missing positional argument (missing positional error) - Spreading arguments to a command that doesn't have a rest parameter but does allow unknown arguments, such as `exec` (allowed) - Spreading a list literal containing arguments of the wrong type (parse error) - Spreading a non-list value, both to internal and external commands - Having named arguments in the middle of rest arguments - `explain`ing a command call that spreads its arguments # 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. --> # Examples Suppose you have multiple tables: ```nushell let people = [[id name age]; [0 alice 100] [1 bob 200] [2 eve 300]] let evil_twins = [[id name age]; [0 ecila 100] [-1 bob 200] [-2 eve 300]] ``` Maybe you often find yourself needing to merge multiple tables and want a utility to do that. You could write a function like this: ```nushell def merge_all [ ...tables ] { $tables | reduce { |it, acc| $acc | merge $it } } ``` Then you can use it like this: ```nushell > merge_all ...([$people $evil_twins] | each { |$it| $it | select name age }) ╭───┬───────┬─────╮ │ # │ name │ age │ ├───┼───────┼─────┤ │ 0 │ ecila │ 100 │ │ 1 │ bob │ 200 │ │ 2 │ eve │ 300 │ ╰───┴───────┴─────╯ ``` Except they had duplicate columns, so now you first want to suffix every column with a number to tell you which table the column came from. You can make a command for that: ```nushell def select_and_merge [ --cols: list<string>, ...tables ] { let renamed_tables = $tables | enumerate | each { |it| $it.item | select $cols | rename ...($cols | each { |col| $col + ($it.index | into string) }) }; merge_all ...$renamed_tables } ``` And call it like this: ```nushell > select_and_merge --cols [name age] $people $evil_twins ╭───┬───────┬──────┬───────┬──────╮ │ # │ name0 │ age0 │ name1 │ age1 │ ├───┼───────┼──────┼───────┼──────┤ │ 0 │ alice │ 100 │ ecila │ 100 │ │ 1 │ bob │ 200 │ bob │ 200 │ │ 2 │ eve │ 300 │ eve │ 300 │ ╰───┴───────┴──────┴───────┴──────╯ ``` --- Suppose someone's made a command to search for APT packages: ```nushell # The main command def search-pkgs [ --install # Whether to install any packages it finds log_level: int # Pretend it's a good idea to make this a required positional parameter exclude?: list<string> # Packages to exclude repositories?: list<string> # Which repositories to look in (searches in all if not given) ...pkgs # Package names to search for ] { { install: $install, log_level: $log_level, exclude: ($exclude | to nuon), repositories: ($repositories | to nuon), pkgs: ($pkgs | to nuon) } } ``` It has a lot of parameters to configure it, so you might make your own helper commands to wrap around it for specific cases. Here's one example: ```nushell # Only look for packages locally def search-pkgs-local [ --install # Whether to install any packages it finds log_level: int exclude?: list<string> # Packages to exclude ...pkgs # Package names to search for ] { # All required and optional positional parameters are given search-pkgs --install=$install $log_level [] ["<local URI or something>"] ...$pkgs } ``` And you can run it like this: ```nushell > search-pkgs-local --install=false 5 ...["python2.7" "vim"] ╭──────────────┬──────────────────────────────╮ │ install │ false │ │ log_level │ 5 │ │ exclude │ [] │ │ repositories │ ["<local URI or something>"] │ │ pkgs │ ["python2.7", vim] │ ╰──────────────┴──────────────────────────────╯ ``` One thing I realized when writing this was that if we decide to not allow passing optional arguments using the spread operator, then you can (mis?)use the spread operator to skip optional parameters. Here, I didn't want to give `exclude` explicitly, so I used a spread operator to pass the packages to install. Without it, I would've needed to do `search-pkgs-local --install=false 5 [] "python2.7" "vim"` (explicitly pass `[]` (or `null`, in the general case) to `exclude`). There are probably more idiomatic ways to do this, but I just thought it was something interesting. If you're a virologist of the [xkcd](https://xkcd.com/350/) kind, another helper command you might make is this: ```nushell # Install any packages it finds def live-dangerously [ ...pkgs ] { # One optional argument was given (exclude), while another was not (repositories) search-pkgs 0 [] ...$pkgs --install # Flags can go after spread arguments } ``` Running it: ```nushell > live-dangerously "git" "*vi*" # *vi* because I don't feel like typing out vim and neovim ╭──────────────┬─────────────╮ │ install │ true │ │ log_level │ 0 │ │ exclude │ [] │ │ repositories │ null │ │ pkgs │ [git, *vi*] │ ╰──────────────┴─────────────╯ ``` Here's an example that uses the spread operator more than once within the same command call: ```nushell let extras = [ chrome firefox python java git ] def search-pkgs-curated [ ...pkgs ] { (search-pkgs 1 [emacs] ["example.com", "foo.com"] vim # A must for everyone! ...($pkgs | filter { |p| not ($p | str contains "*") }) # Remove packages with globs python # Good tool to have ...$extras --install=false python3) # I forget, did I already put Python in extras? } ``` Running it: ```nushell > search-pkgs-curated "git" "*vi*" ╭──────────────┬───────────────────────────────────────────────────────────────────╮ │ install │ false │ │ log_level │ 1 │ │ exclude │ [emacs] │ │ repositories │ [example.com, foo.com] │ │ pkgs │ [vim, git, python, chrome, firefox, python, java, git, "python3"] │ ╰──────────────┴───────────────────────────────────────────────────────────────────╯ ``` |
||
|---|---|---|
| .. | ||
| fuzz | ||
| src | ||
| tests | ||
| Cargo.toml | ||
| LICENSE | ||
| README.md | ||
nu-parser, the Nushell parser
Nushell's parser is a type-directed parser, meaning that the parser will use type information available during parse time to configure the parser. This allows it to handle a broader range of techniques to handle the arguments of a command.
Nushell's base language is whitespace-separated tokens with the command (Nushell's term for a function) name in the head position:
head1 arg1 arg2 | head2
Lexing
The first job of the parser is to a lexical analysis to find where the tokens start and end in the input. This turns the above into:
<item: "head1">, <item: "arg1">, <item: "arg2">, <pipe>, <item: "head2">
At this point, the parser has little to no understanding of the shape of the command or how to parse its arguments.
Lite parsing
As Nushell is a language of pipelines, pipes form a key role in both separating commands from each other as well as denoting the flow of information between commands. The lite parse phase, as the name suggests, helps to group the lexed tokens into units.
The above tokens are converted the following during the lite parse phase:
Pipeline:
Command #1:
<item: "head1">, <item: "arg1">, <item: "arg2">
Command #2:
<item: "head2">
Parsing
The real magic begins to happen when the parse moves on to the parsing stage. At this point, it traverses the lite parse tree and for each command makes a decision:
- If the command looks like an internal/external command literal: e.g.
fooor/usr/bin/ls, it parses it as an internal or external command - Otherwise, it parses the command as part of a mathematical expression
Types/shapes
Each command has a shape assigned to each of the arguments it reads in. These shapes help define how the parser will handle the parse.
For example, if the command is written as:
where $x > 10
When the parsing happens, the parser will look up the where command and find its Signature. The Signature states what flags are allowed and what positional arguments are allowed (both required and optional). Each argument comes with a Shape that defines how to parse values to get that position.
In the above example, if the Signature of where said that it took three String values, the result would be:
CallInfo:
Name: `where`
Args:
Expression($x), a String
Expression(>), a String
Expression(10), a String
Or, the Signature could state that it takes in three positional arguments: a Variable, an Operator, and a Number, which would give:
CallInfo:
Name: `where`
Args:
Expression($x), a Variable
Expression(>), an Operator
Expression(10), a Number
Note that in this case, each would be checked at compile time to confirm that the expression has the shape requested. For example, "foo" would fail to parse as a Number.
Finally, some Shapes can consume more than one token. In the above, if the where command stated it took in a single required argument, and that the Shape of this argument was a MathExpression, then the parser would treat the remaining tokens as part of the math expression.
CallInfo:
Name: `where`
Args:
MathExpression:
Op: >
LHS: Expression($x)
RHS: Expression(10)
When the command runs, it will now be able to evaluate the whole math expression as a single step rather than doing any additional parsing to understand the relationship between the parameters.
Making space
As some Shapes can consume multiple tokens, it's important that the parser allow for multiple Shapes to coexist as peacefully as possible.
The simplest way it does this is to ensure there is at least one token for each required parameter. If the Signature of the command says that it takes a MathExpression and a Number as two required arguments, then the parser will stop the math parser one token short. This allows the second Shape to consume the final token.
Another way that the parser makes space is to look for Keyword shapes in the Signature. A Keyword is a word that's special to this command. For example in the if command, else is a keyword. When it is found in the arguments, the parser will use it as a signpost for where to make space for each Shape. The tokens leading up to the else will then feed into the parts of the Signature before the else, and the tokens following are consumed by the else and the Shapes that follow.