forked from extern/nushell
d0a2a02eea
* Add possibility to declare optional parameters and switch flags
With this commit applied it is now possible to specify optional parameters and flags
as switches. This PR **only** makes guarantees about **parsing** optional flags and
switches correctly. This PR **does not guarantee flawless functionality** of
optional parameters / switches within scripts.
functionality within scripts. Example:
test.nu
```shell
def my_command [
opt_param?
opt_param2?: int
--switch
] {echo hi nushell}
```
```shell
> source test.nu
> my_command -h
───┬─────────
0 │ hi
1 │ nushell
───┴─────────
Usage:
> my_command <mandatory_param> (opt_param) (opt_param2) {flags}
Parameters:
<mandatory_param>
(opt_param)
(opt_param2)
Flags:
-h, --help: Display this help message
--switch
--opt_flag <any>
```
* Update def docs
74 lines
1.7 KiB
Markdown
74 lines
1.7 KiB
Markdown
# def
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Use `def` to create a custom command.
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## Examples
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```shell
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> def my_command [] { echo hi nu }
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> my_command
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hi nu
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```
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```shell
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> def my_command [adjective: string, num: int] { echo $adjective $num meet nu }
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> my_command nice 2
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nice 2 meet nu
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```
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```shell
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def my_cookie_daemon [
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in: path # Specify where the cookie daemon shall look for cookies :p
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...rest: path # Other places to consider for cookie supplies
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--output (-o): path # Where to store leftovers
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--verbose
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] {
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echo $in $rest | each { eat $it }
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...
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}
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my_cookie_daemon /home/bob /home/alice --output /home/mallory
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```
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Further (and non trivial) examples can be found in our [nushell scripts repo](https://github.com/nushell/nu_scripts)
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## Syntax
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The syntax of the def command is as follows.
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`def <name> <signature> <block>`
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The signature is a list of parameters flags and at maximum one rest argument. You can specify the type of each of them by appending `: <type>`.
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Example:
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```shell
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def cmd [
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parameter: string
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--flag: int
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...rest: path
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] { ... }
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```
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It is possible to comment them by appending `# Comment text`!
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Example
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```shell
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def cmd [
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parameter # Paramter Comment
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--flag: int # Flag comment
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...rest: path # Rest comment
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] { ... }
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```
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Flags can have a single character shorthand form. For example `--output` is often abbreviated by `-o`. You can declare a shorthand by writing `(-<shorthand>)` after the flag name.
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Example
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```shell
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def cmd [
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--flag(-f): int # Flag comment
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] { ... }
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```
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You can make a parameter optional by adding `?` to its name. Optional parameters do not need to be passed.
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(TODO Handling optional parameters in scripts is WIP. Please don't expect it to work seamlessly)
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```shell
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def cmd [
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parameter?: path # Optional parameter
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] { ... }
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```
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