fish-shell/doc_src/cmds/fish_command_not_found.rst
Fabian Homborg 340de73172 Call "fish_command_not_found" if a command wasn't found
Previously, when a command wasn't found, fish would emit the
"fish_command_not_found" *event*.

This was annoying as it was hard to override (the code ended up
checking for a function called `__fish_command_not_found_handler`
anyway!), the setup was ugly,
and it's useless - there is no use case for multiple command-not-found handlers.

Instead, let's just call a function `fish_command_not_found` if it
exists, or print the default message otherwise.

The event is completely removed, but because a missing event is not an error
(MEISNAE in C++-speak) this isn't an issue.

Note that, for backwards-compatibility, we still keep the default
handler function around even tho the new one is hard-coded in C++.

Also, if we detect a previous handler, the new handler just calls it.

This way, the backwards-compatible way to install a custom handler is:

```fish
function __fish_command_not_found_handler --on-event fish_command_not_found
    # do a little dance, make a little love, get down tonight
end
```

and the new hotness is

```fish
function fish_command_not_found
    # do the thing
end
```

Fixes #7293.
2020-09-06 11:15:54 +02:00

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ReStructuredText

.. _cmd-fish_cmd_not_found:
fish_command_not_found - what to do when a command wasn't found
===============================================================
Synopsis
--------
::
function fish_command_not_found
...
end
Description
-----------
When fish tries to execute a command and can't find it, it invokes this function.
It can print a message to tell you about it, and it often also checks for a missing package that would include the command.
Fish ships multiple handlers for various operating systems and chooses from them when this function is loaded,
or you can define your own.
It receives the full commandline as one argument per token, so $argv[1] contains the missing command.
When you leave ``fish_command_not_found`` undefined (e.g. by adding an empty function file) or explicitly call ``__fish_default_command_not_found_handler``, fish will just print a simple error.
Example
-------
A simple handler:
::
function fish_command_not_found
echo Did not find command $argv[1]
end
> flounder
Did not find command flounder
Or the handler for OpenSUSE's command-not-found::
function fish_command_not_found
/usr/bin/command-not-found $argv[1]
end
Or the simple default handler::
function fish_command_not_found
__fish_default_command_not_found_handler $argv
end
Backwards compatibility
-----------------------
This command was introduced in fish 3.2.0. Previous versions of fish used the "fish_command_not_found" :ref:`event <event>` instead.
To define a handler that works in older versions of fish as well, define it the old way::
function __fish_command_not_found_handler --on-event fish_command_not_found
echo COMMAND WAS NOT FOUND MY FRIEND $argv[1]
end
in which case fish will define a ``fish_command_not_found`` that calls it,
or define a wrapper::
function fish_command_not_found
echo "G'day mate, could not find your command: $argv"
end
function __fish_command_not_found_handler --on-event fish_command_not_found
fish_command_not_found $argv
end