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fix: rework developers.md

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* Fixed some grammar and tried to simplify the technical wording

* Fixed the mistake of calling `map` a table instead of a function

* Removed line about passing display to display
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Julian Fricker
2021-09-16 09:04:56 +01:00
committed by Simon Hauser
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developers.md
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@@ -20,19 +20,19 @@
So you want to develop your own picker and/or extension for telescope? Then you
are in the right place! This file will first present an introduction on how to
do this. After that, this document will present a technical explanation of
pickers, finders, actions, and the previewer. You will find more information
in specific help pages and we likely will move some of the technical stuff to
pickers, finders, actions and the previewer. You can find more information
in specific help pages and we will probably move some of the technical stuff to
our vim help docs in the future.
This guide is mainly for telescope so it will assume that a lua knowledge is
present. You can find information for lua here:
This guide is mainly for telescope so it will assume that you already have some knowledge of the Lua
programming language. If not then you can find information for Lua here:
- [Lua 5.1 Manual](https://www.lua.org/manual/5.1/)
- [Getting started using Lua in Neovim](https://github.com/nanotee/nvim-lua-guide)
## Guide to your first Picker
To guide you along the way to first picker we will do the following. We will
open a empty lua scratch file in which we will develop the picker and run it
open an empty lua scratch file in which we will develop the picker and run it
each time using `:luafile %`. Later this file then be bundled as extension.
### Requires
@@ -46,13 +46,13 @@ local conf = require("telescope.config").values
- `pickers` is the main module which is used to create a new picker.
- `finders` provides interfaces to fill the picker with items.
- `config` which is used for user configuration and the `values` table holds
these configurations. So to make it easier we only get this table in `conf`.
- `config` the `values` table holds the user configuration.
So to make it easier we access this table directly in `conf`.
### First Picker
We will now make the most simplest color picker. (Note that the previous snippet
is also required. We will approach this example step by step).
We will now make the simplest color picker. (We will approach this example step by step,
you will still need to have the previous requires section above this code.)
```lua
-- our picker function: colors
@@ -70,35 +70,38 @@ end
colors()
```
Running this file should open a telescope picker with the entries `red`,
`green`, `blue`. Pressing enter will open a new file, depending which element is
selected, in this case this is not what we want so we will address this after
explaining this snippet.
Running this code with `:luafile %` should open a telescope picker with the entries `red`,
`green`, `blue`. Selecting a color and pressing enter will open a new file, in this case
it's not what we want so we will address this after explaining this snippet.
We will define a new function which will take in a table `opts`. This is good
practice because now the user can define the behavior of the picker, for example
change the theme. That the user is able to change the theme we need to pass in
`opts` as the first argument to `pickers.new`. The second argument is a table
that defines the default behavior of the picker.
We will define a new function `colors` which accepts a table `opts`. This is good
practice because now the user can change how telescope behaves by passing in their
own `opts` table when calling `colors`.
We can define a `prompt_title`, this option is not required, default will be
`Prompt` if not set.
For example the user can pass in a configuration in `opts` which allows them to change
the theme used for the picker. To allow this we have to make sure we pass the `opts` table
as the first argument to `pickers.new`. The second argument is a table
which defines the default behavior of the picker.
We have defined a `prompt_title` but this isn't required. This will default to use
the text `Prompt` if not set.
`finder` is a required field that needs to be set to the result of a `finders`
function. In this case we take `new_table` which allows us to define a static
set of values, `results`, which is a array of elements, in this case our colors
as strings. It doesn't have to be a array of strings, it can also be a array of
tables. More to this later.
set of values, `results`, which is an array of elements, in this case our colors
as strings. It doesn't have to be an array of strings, it can also be an array of
tables. More on this later.
`sorter` on the other hand is not a required field but its good practice to
`sorter` on the other hand is not a required field but it's good practice to
define it, because the default value will set it to `empty()`, meaning no sorter
is attached and you can't filter the results. Good practice is to set the sorter
to either `conf.generic_sorter(opts)` or `conf.file_sorter(opts)`. Setting it to
a `conf` value will respect user configuration, so if a user has setup
`fzf-native` as sorter then this decision will be respected and the fzf sorter
will be attached. Its also suggested to pass in opts here because the sorter
to either `conf.generic_sorter(opts)` or `conf.file_sorter(opts)`.
Setting it to a value from `conf` will respect the user's configuration, so if a user has set-up
`fzf-native` as the sorter then this decision will be respected and the `fzf-native` sorter
will be attached. It's also suggested to pass in `opts` here because the sorter
could make use of it. As an example the fzf sorter can be configured to be case
sensitive or insensitive. A user can setup a default behavior and then alter
sensitive or insensitive. A user can set-up a default behavior and then alter
this behavior with the `opts` table.
After the picker is defined you need to call `find()` to actually start the
@@ -115,13 +118,13 @@ the last line with the following to open the picker with the `dropdown` theme.
colors(require("telescope.themes").get_dropdown{})
```
Now lets address the issue that selecting a color opens a new buffer. For that
we need to replace the default select action. The benefit of replace rather than
Now let's address the issue that selecting a color opens a new buffer. For that
we need to replace the default select action. The benefit of replacing rather than
mapping a new function to `<CR>` is that it will respect user configuration. So
if a user has remapped `select_default` to another key then this decision will
be respected and it works as expected for the user.
To make this work we need more includes at the top of the file.
To make this work we need more requires at the top of the file.
```lua
local actions = require "telescope.actions"
@@ -132,11 +135,11 @@ local action_state = require "telescope.actions.state"
access the default action so we can replace it. Also see `:help
telescope.actions`
- `action_state` gives us a couple of util function we can use to get the
- `action_state` gives us a few utility functions we can use to get the
current picker, current selection or current line. Also see `:help
telescope.actions.state`
So lets replace the default action. For that we need to define a new key value
So let's replace the default action. For that we need to define a new key value
pair in our table that we pass into `pickers.new`, for example after `sorter`.
```lua
@@ -151,41 +154,45 @@ pair in our table that we pass into `pickers.new`, for example after `sorter`.
end,
```
So we do this by setting the `attach_mappings` key to a function. This function
We do this by setting the `attach_mappings` key to a function. This function
needs to return either `true` or `false`. If it returns false it means that only
the actions defined in the function should be attached. So no
`move_selection_{next,previous}`, so most of the cases you want that this
function returns `true`. If the function does not return anything a error is
thrown. The `attach_mappings` function will get to parameters passed in
`prompt_bufnr` the buffer number of the prompt buffer, which we can use to get
the pickers object, and `map` a function we can use to map actions or functions
to arbitrary key sequences.
the actions defined in the function should be attached. In this case it would
remove the default actions to move the selected item in the picker,
`move_selection_{next,previous}`. So in most cases you'll want to return `true`.
If the function does not return anything then an error is thrown.
Now we are replacing `select_default` the default action that happens on `<CR>`
(if not remapped). To do so we need to call `actions.select_default:replace` and
pass in a new function. In this new function we first close the picker with
`actions.close` and then get the `selection` with `action_state`. Its important
The `attach_mappings` function has two parameters, `prompt_bufnr` is the buffer number
of the prompt buffer, which we can use to get the pickers object and `map` is a function
we can use to map actions or functions to arbitrary key sequences.
Now we are replacing `select_default` the default action, which is mapped to `<CR>`
by default. To do this we need to call `actions.select_default:replace` and
pass in a new function.
In this new function we first close the picker with `actions.close` and then
get the `selection` with `action_state`. It's important
to notice that you can still get the selection and current prompt input
(`action_state.get_current_line()`) with `action_state` even tho the picker is
already closed. You can look at the selection with
`print(vim.inspect(selection))` and you will see that it differs from our input
(string), this is because we will internally pack it in a table with different
keys. You can specify this behavior and we will talk about that in the next
section. Now all that is left is to do anything with the selection we have. In
this case we just put the text in the current buffer.
(`action_state.get_current_line()`) with `action_state` even after the picker is
closed.
You can look at the selection with `print(vim.inspect(selection))` and see that it differs from our input
(string), this is because internally we pack it into a table with different
keys. You can specify this behavior and wel'l talk about that in the next
section. Now all that is left is to do something with the selection we have. In
this case we just put the text in the current buffer with `vim.api.nvim_put`.
### Entry Maker
Entry maker is a function that is used to transform a item from the finder to a
internal entry table, which has a couple of required keys. It allows to have a
different display and match something completly different. It also allows to set
a absolute path (so the file will always be found) and a relative file path as
display and for sorting. This allows that the relative file path doesn't even
have to be valid in the context of the current working directory.
Entry maker is a function used to transform an item from the finder to an
internal entry table, which has a few required keys. It allows us to display
one string but match something completly different. It also allows us to set
an absolute path when working with files (so the file will always be found)
and a relative file path for display and sorting. This means the relative file
path doesn't even need to be valid in the context of the current working directory.
We will now try to define a our entry maker for our example by providing a
We will now try to define our entry maker for our example by providing an
`entry_maker` to `finders.new_table` and changing our table to be a little bit
more interesting. We will end up following new input for `finders.new_table`:
more interesting. We will end up with the following new code for `finders.new_table`:
```lua
finder = finders.new_table {
@@ -204,29 +211,34 @@ more interesting. We will end up following new input for `finders.new_table`:
},
```
With the new snippet we now no longer have a array of strings but a array of
tables. Each table has a color name and the hex value.
With the new snippet we no longer have an array of strings but an array of
tables. Each table has a color name and the color's hex value.
`entry_maker` is a function that will receive each table and then we can set the
values we want to set. Its best practice to have a `value` reference to the
original entry, that way you can access the whole table in your action later.
values we need. It's best practice to have a `value` reference to the
original entry, that way we will always have access to the complete table in our
action.
The first required key is `display` and is either a string or a `function(tbl)`,
where `tbl` the table that is returned by `entry_maker`. For a lot of values its
suggested to have display as function especially if you are modifying it because
then the function will only be executed for the entries that are being
displayed. For examples of entry maker take a look at
`lua/telescope/make_entry.lua`. A good way to make your `display` more like a
table is to use `displayer` which can be found in
`lua/telescope/entry_display.lua`. A more simple example of `displayer` is the
The `display` key is required and is either a string or a `function(tbl)`,
where `tbl` is the table returned by `entry_maker`. So in this example `tbl` would
give our `display` function access to `value` and `ordinal`.
If our picker will have a lot lot of values it's suggested to use a function for `display`
especially if you are modifying the text to display. This way the function will only be executed
for the entries being displayed. For an examples of an entry maker take a look at
`lua/telescope/make_entry.lua`.
A good way to make your `display` more like a table is to use a `displayer` which can be found in
`lua/telescope/entry_display.lua`. A simpler example of `displayer` is the
function `gen_from_git_commits` in `make_entry.lua`.
The second required key is `ordinal`, which is used for sorting. So you can have
different display and sorting values. This allows `display` to be more fancier
with icons and special indicators and a separate sorting key.
The `ordinal` is also required, which is used for sorting. As already mentioned
this allows us to have different display and sorting values. This allows `display`
to be more complex with icons and special indicators but `ordinal` could be a simpler
sorting key.
There are more important keys which can be set but do not make sense in the
current context:
There are other important keys which can be set but do not make sense in the
current context as we are not dealing wiht files:
- `path`: to set the absolute path of the file to make sure its always found
- `lnum`: to specify a line number in the file. This will allow the
`conf.grep_previewer` to show that line and the default action to jump to
@@ -234,16 +246,16 @@ current context:
### Previewer
We will not write a previewer for this picker because it makes less sense and is
a more advanced topic. Its already documented pretty good under `:help
telescope.previewers` so you should read this section if you want to write your
own `previewer`. If you want a file previewer with or without col you should
We will not write a previewer for this picker because it isn't required for
basic colors and is a more advanced topic. It's already well documented in `:help
telescope.previewers` so you can read this section if you want to write your
own `previewer`. If you want a file previewer without columns you should
default to `conf.file_previewer` or `conf.grep_previewer`.
### Oneshot Job
The `oneshot_job` finder can be used to have a async external process which will
produce results and call `entry_maker` on each new line. Example usage would be
The `oneshot_job` finder can be used to have an asynchronous external process which will
find results and call `entry_maker` for each entry. An example usage would be
`find`.
```lua
@@ -253,14 +265,14 @@ finder = finders.new_oneshot_job { "find", opts },
### More examples
A good way to find more examples is to look into the `lua/telescope/builtin/`
directory which contains all builtin pickers. Another way to find more examples
directory which contains all of the builtin pickers. Another way to find more examples
is to take a look at the [extension wiki page](https://github.com/nvim-telescope/telescope.nvim/wiki/Extensions)
and then at a extension some wrote.
as this provides many extensions peopel have already written which use these concepts.
If you still have questions after reading this guide feel free to ask us for
If you still have any questions after reading this guide please feel free to ask us for
more information on [gitter](https://gitter.im/nvim-telescope/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
and we happily answer your questions and potentially even improve this guide. Of
course you can also improve this guide by sending a PRs.
and we will happily answer your questions and hopefully allow us to improve this guide. You can also
help us to improve this guide by sending a PRs.
## Technical
@@ -283,7 +295,7 @@ Picker:new{
```
### Finders
<!-- TODO what is finders -->
<!-- TODO what are finders -->
```lua
-- lua/telescope/finders.lua
Finder:new{
@@ -309,8 +321,8 @@ TODO: Talk about what actions vs actions sets are
- `lua/telescope/actions/set.lua`
- The second most "user-facing" of the files. This provides actions that are consumed by several builtin actions, which allows for only overriding ONE item, instead of copying the same configuration / function several times.
- `lua/telescope/actions/state.lua`
- Provides APIs for interacting with the state of telescope while in actions.
- These are most useful for writing your own actions and interacting with telescope at that time
- Provides APIs for interacting with the state of telescope from within actions.
- These are useful for writing your own actions and interacting with telescope
- `lua/telescope/actions/mt.lua`
- You probably don't need to look at this, but it defines the behavior of actions.