path: root/2020/subtitles/emacsconf-2020--23-incremental-parsing-with-emacs-tree-sitter--tuan-anh-nguyen.vtt

WEBVTT

00:00:01.520 --> 00:00:04.400
Hello, everyone! My name is Tuấn-Anh.

00:00:04.400 --> 00:00:07.200
I've been using Emacs for about 10 years.

00:00:07.200 --> 00:00:09.280
Today, I'm going to talk about tree-sitter,

00:00:09.280 --> 00:00:11.351
a new Emacs package that allows Emacs

00:00:11.351 --> 00:00:17.840
to parse multiple programming languages
in real-time.

00:00:17.840 --> 00:00:21.840
So what is the problem statement?

00:00:21.840 --> 00:00:24.131
In order to support programming
functionalities

00:00:24.131 --> 00:00:25.760
for a particular language,

00:00:25.760 --> 00:00:27.680
a text editor needs to have some degree

00:00:27.680 --> 00:00:29.679
of language understanding.

00:00:29.679 --> 00:00:31.840
Traditionally, text editors have relied

00:00:31.840 --> 00:00:34.960
very heavily on regular expressions for
this.

00:00:34.960 --> 00:00:37.013
Emacs is no different.

00:00:37.013 --> 00:00:40.170
Most language major modes use regular
expressions

00:00:40.170 --> 00:00:42.960
for syntax-highlighting, code navigation,

00:00:42.960 --> 00:00:46.618
folding, indexing, and so on.

00:00:46.618 --> 00:00:50.559
Regular expressions are problematic for
a couple of reasons.

00:00:50.559 --> 00:00:53.778
They're slow and inaccurate.

00:00:53.778 --> 00:00:56.800
They also make the code hard to read and
write.

00:00:56.800 --> 00:01:01.199
Sometimes it's because the regular
expressions themselves are very hairy,

00:01:01.199 --> 00:01:05.199
and sometimes because they are just not
powerful enough.

00:01:05.199 --> 00:01:08.625
Some helper code is usually needed

00:01:08.625 --> 00:01:11.200
to parse more intricate language
features.

00:01:11.200 --> 00:01:16.159
That also illustrates the core problem
with regular expressions,

00:01:16.159 --> 00:01:21.119
in that they are not powerful enough to
parse programming languages.

00:01:21.119 --> 00:01:25.040
An example feature that regular
expressions cannot handle very well

00:01:25.040 --> 00:01:28.320
is string interpolation, which is a very
common feature

00:01:28.320 --> 00:01:31.680
in many modern programming languages.

00:01:31.680 --> 00:01:34.079
It would be much nicer if Emacs somehow

00:01:34.079 --> 00:01:39.520
had structural understanding of source
code, like IDEs do.

00:01:39.520 --> 00:01:41.981
There have been multiple efforts

00:01:41.981 --> 00:01:45.280
to bring this kind of programming
language understanding into Emacs.

00:01:45.280 --> 00:01:47.119
There are language-specific parsers

00:01:47.119 --> 00:01:48.640
written in Elisp

00:01:48.640 --> 00:01:50.675
that can be thought of

00:01:50.675 --> 00:01:51.989
as the next logical step
of the glue code

00:01:51.989 --> 00:01:53.856
on top of regular expressions,

00:01:53.856 --> 00:01:57.356
moving from partial local pattern
recognition

00:01:57.356 --> 00:01:59.840
into a full-fledged parser.

00:01:59.840 --> 00:02:02.023
The most prominent example of this
approach

00:02:02.023 --> 00:02:06.479
is probably the famous js2-mode.

00:02:06.479 --> 00:02:10.080
However, this approach has several issues.

00:02:10.080 --> 00:02:12.606
Parsing is computationally expensive,

00:02:12.606 --> 00:02:16.800
and Emacs Lisp is not good at that kind
of stuff.

00:02:16.800 --> 00:02:19.156
Furthermore, maintenance is very
troublesome.

00:02:19.156 --> 00:02:22.160
In order to work on these parsers,

00:02:22.160 --> 00:02:24.239
first, you have to know Elisp
well enough,

00:02:24.239 --> 00:02:26.606
and then you have to be comfortable with

00:02:26.606 --> 00:02:29.739
writing a recursive descending parser,

00:02:29.739 --> 00:02:34.000
while constantly keeping up with changes
to the language itself,

00:02:34.000 --> 00:02:36.356
which can be evolving very quickly,

00:02:36.356 --> 00:02:39.360
like Javascript, for example.

00:02:39.360 --> 00:02:42.373
Together, these constraints
significantly reduce

00:02:42.373 --> 00:02:45.680
the pool of potential maintainers.

00:02:45.680 --> 00:02:47.760
The biggest issue, though, in my opinion,

00:02:47.760 --> 00:02:52.139
is lack of the set of generic and
reusable APIs.

00:02:52.139 --> 00:02:54.319
This makes them very hard to use

00:02:54.319 --> 00:02:55.920
for minor modes that want to deal with

00:02:55.920 --> 00:02:59.920
cross-cutting concerns across multiple
languages.

00:02:59.920 --> 00:03:01.760
The other approach which has been

00:03:01.760 --> 00:03:04.319
gaining a lot of momentum
in recent years

00:03:04.319 --> 00:03:06.560
is externalizing language understanding

00:03:06.560 --> 00:03:08.159
to another process,

00:03:08.159 --> 00:03:12.239
also known as language server protocol.

00:03:12.239 --> 00:03:16.560
This second approach is actually a very
interesting one.

00:03:16.560 --> 00:03:18.400
By decoupling language understanding

00:03:18.400 --> 00:03:21.280
from the editing facility itself,

00:03:21.280 --> 00:03:25.120
the LSP servers can attract a lot more
contributors,

00:03:25.120 --> 00:03:27.189
which makes maintenance easier.

00:03:27.189 --> 00:03:32.400
However, they also have several issues
of their own.

00:03:32.400 --> 00:03:34.089
Being a separate process,

00:03:34.089 --> 00:03:37.073
they are usually more
resource-intensive,

00:03:37.073 --> 00:03:39.920
and depending on the language,

00:03:39.920 --> 00:03:42.159
the LSP server itself can bring with it

00:03:42.159 --> 00:03:44.640
a host of additional dependencies

00:03:44.640 --> 00:03:50.640
external to Emacs, which may be messy to
install and manage.

00:03:50.640 --> 00:03:55.120
Furthermore, JSON over RPC has pretty
high latency.

00:03:55.120 --> 00:03:57.840
For one-off tasks like jumping to source

00:03:57.840 --> 00:04:00.879
or on-demand completion, it's great.

00:04:00.879 --> 00:04:03.040
But for things like code highlighting,

00:04:03.040 --> 00:04:06.000
the latency is just too much.

00:04:06.000 --> 00:04:08.319
I was using Rust and I was following the

00:04:08.319 --> 00:04:11.760
community effort to improve its
IDE support,

00:04:11.760 --> 00:04:15.760
hoping to integrate some of that into
Emacs itself.

00:04:15.760 --> 00:04:19.759
Then I heard someone from the community
mention tree-sitter,

00:04:19.759 --> 00:04:23.360
and I decided to check it out.

00:04:23.360 --> 00:04:28.720
Basically, tree-sitter is an incremental
parsing library and a parser generator.

00:04:28.720 --> 00:04:33.040
It was introduced by the Atom editor in
2018.

00:04:33.040 --> 00:04:35.923
Besides Atom, it is also being
integrated

00:04:35.923 --> 00:04:37.623
into the NeoVim editor,

00:04:37.623 --> 00:04:41.040
and Github is using it to power

00:04:41.040 --> 00:04:42.423
their source code analysis

00:04:42.423 --> 00:04:45.840
and navigation features.

00:04:45.840 --> 00:04:48.639
It is written in C and can be compiled

00:04:48.639 --> 00:04:50.623
for all major platforms.

00:04:50.623 --> 00:04:53.120
It can even be compiled

00:04:53.120 --> 00:04:55.323
to web assembly to run on the web.

00:04:55.323 --> 00:05:00.800
That's how Github is using it
on their website.

00:05:00.800 --> 00:05:05.840
So why is tree-sitter an interesting
solution to this problem?

00:05:05.840 --> 00:05:10.000
There are multiple features that make it
an attractive option.

00:05:10.000 --> 00:05:11.839
It is designed to be fast.

00:05:11.839 --> 00:05:13.680
By being incremental,

00:05:13.680 --> 00:05:15.680
the initial parse of a typical big file

00:05:15.680 --> 00:05:18.160
can take tens of milliseconds,

00:05:18.160 --> 00:05:20.240
while subsequent incremental processes

00:05:20.240 --> 00:05:22.560
are sub-millisecond.

00:05:22.560 --> 00:05:26.240
It achieves this by using
structural sharing,

00:05:26.240 --> 00:05:29.360
meaning replacing only affected nodes

00:05:29.360 --> 00:05:32.960
in the old tree when it needs to.

00:05:32.960 --> 00:05:37.120
Also, unlike LSP, being in
the same process,

00:05:37.120 --> 00:05:40.639
it has much lower latency.

00:05:40.639 --> 00:05:44.960
Secondly, it provides a uniform
programming interface.

00:05:44.960 --> 00:05:47.039
The same data structures and functions

00:05:47.039 --> 00:05:50.400
work on parse trees of different
languages.

00:05:50.400 --> 00:05:52.160
Syntax nodes of different languages

00:05:52.160 --> 00:05:54.160
differ only by their types

00:05:54.160 --> 00:05:55.723
and their possible child nodes.

00:05:55.723 --> 00:06:02.240
This is a big advantage over
language-specific parsers.

00:06:02.240 --> 00:06:06.880
Thirdly, it's written in self-contained
embeddable C.

00:06:06.880 --> 00:06:11.723
As I mentioned previously, it can even
be compiled to webassembly.

00:06:11.723 --> 00:06:16.106
This makes integrating it into various
editors quite easy

00:06:16.106 --> 00:06:22.880
without having to install any external
dependencies.

00:06:22.880 --> 00:06:25.503
One thing that is not mentioned here

00:06:25.503 --> 00:06:28.000
is that being a parser generator,

00:06:28.000 --> 00:06:31.039
its grammars are declarative.

00:06:31.039 --> 00:06:34.880
Together with being editor-independent,

00:06:34.880 --> 00:06:39.139
this makes the pool of potential
contributors much larger.

00:06:39.139 --> 00:06:45.520
So I was convinced that tree-sitter is a
good fit for Emacs.

00:06:45.520 --> 00:06:48.000
Last year, I started writing the bindings

00:06:48.000 --> 00:06:53.280
using dynamic module support introduced
in Emacs 25.

00:06:53.280 --> 00:06:58.479
Dynamic module means there is
platform-specific native code involved,

00:06:58.479 --> 00:07:00.560
but since there are pre-compiled binaries

00:07:00.560 --> 00:07:02.880
for the three major platforms,

00:07:02.880 --> 00:07:04.706
it should work in most places.

00:07:04.706 --> 00:07:09.440
Currently, the core functionalities are
in a pretty good shape.

00:07:09.440 --> 00:07:12.560
Syntax highlighting is working nicely.

00:07:12.560 --> 00:07:16.080
The whole thing is split into three
packages.

00:07:16.080 --> 00:07:20.319
tree-sitter is the main package that
other packages should depend on.

00:07:20.319 --> 00:07:22.800
tree-sitter-langs is the language bundle

00:07:22.800 --> 00:07:24.000
that includes support

00:07:24.000 --> 00:07:27.199
for most common languages.

00:07:27.199 --> 00:07:32.160
And finally, the core APIs are in the
package tsc,

00:07:32.160 --> 00:07:36.160
which stands for tree-sitter-core.

00:07:36.160 --> 00:07:38.800
It is the implicit dependency of the

00:07:38.800 --> 00:07:43.520
tree-sitter package.

00:07:43.520 --> 00:07:47.520
The main package includes the minor mode
tree-sitter-mode.

00:07:47.520 --> 00:07:52.560
This provides the base for other major
or minor modes to build on.

00:07:52.560 --> 00:07:54.839
Using Emacs's change tracking hooks,

00:07:54.839 --> 00:07:57.073
it enables incremental parsing

00:07:57.073 --> 00:08:00.800
and provides a syntax tree that is
always up to date

00:08:00.800 --> 00:08:04.080
after any edits in a buffer.

00:08:04.080 --> 00:08:06.223
There is also a basic debug mode

00:08:06.223 --> 00:08:10.080
that shows the parse tree in
another buffer.

00:08:10.080 --> 00:08:13.360
Here is a quick demo.

00:08:13.360 --> 00:08:15.673
Here I'm in an empty Python buffer

00:08:15.673 --> 00:08:17.520
with tree-sitter enabled.

00:08:17.520 --> 00:08:19.440
I'm going to turn on the debug mode to

00:08:19.440 --> 00:08:26.560
see the parse tree.

00:08:26.560 --> 00:08:28.106
Since the buffer is empty,

00:08:28.106 --> 00:08:30.423
there is only one node in the
syntax tree:

00:08:30.423 --> 00:08:33.279
the top-level module node.

00:08:33.279 --> 00:09:11.040
Let's try typing some code.

00:09:11.040 --> 00:09:14.640
As you can see, as I type into the
Python buffer,

00:09:14.640 --> 00:09:19.120
the syntax tree updates in real time.

00:09:19.120 --> 00:09:22.039
The other minor mode included in the
main package

00:09:22.039 --> 00:09:24.389
is tree-sitter-hl-mode.

00:09:24.389 --> 00:09:26.349
It overrides font-lock mode

00:09:26.349 --> 00:09:28.480
and provides its own set of phases

00:09:28.480 --> 00:09:30.139
and customization options

00:09:30.139 --> 00:09:32.800
It is query-driven.

00:09:32.800 --> 00:09:36.240
That means instead of regular
expressions,

00:09:36.240 --> 00:09:39.518
it uses a Lisp-like query language

00:09:39.518 --> 00:09:40.320
to map syntax nodes

00:09:40.320 --> 00:09:41.923
to highlighting phrases.

00:09:41.923 --> 00:09:45.760
I'm going to open a python file with
small snippets

00:09:45.760 --> 00:09:54.320
that showcase syntax highlighting.

00:09:54.320 --> 00:09:55.920
So this is the default highlighting

00:09:55.920 --> 00:10:00.880
provided by python-mode.

00:10:00.880 --> 00:10:04.640
This is the highlighting enabled
by tree-sitter.

00:10:04.640 --> 00:10:07.680
As you can see, string interpolation

00:10:07.680 --> 00:10:11.680
and decorators are highlighted correctly.

00:10:11.680 --> 00:10:17.440
Function calls are also highlighted.

00:10:17.440 --> 00:10:21.839
You can also note that
property accessors

00:10:21.839 --> 00:10:27.440
and property assignments are highlighted
differently.

00:10:27.440 --> 00:10:29.360
What I like the most about this is that

00:10:29.360 --> 00:10:32.640
new bindings are consistently
highlighted.

00:10:32.640 --> 00:10:36.320
This included local variables,

00:10:36.320 --> 00:10:45.760
function parameters, and property
mutations.

00:10:45.760 --> 00:10:48.000
Before going through the tree queries

00:10:48.000 --> 00:10:49.279
and the syntax highlighting

00:10:49.279 --> 00:10:51.680
customization options,

00:10:51.680 --> 00:10:53.339
let's take a brief look at

00:10:53.339 --> 00:10:55.040
the core data structures and functions

00:10:55.040 --> 00:10:58.079
that tree-sitter provides.

00:10:58.079 --> 00:11:00.743
So parsing is done with the help of

00:11:00.743 --> 00:11:02.240
a generic parser object.

00:11:02.240 --> 00:11:04.160
A single parser object can be used to

00:11:04.160 --> 00:11:06.000
parse different languages

00:11:06.000 --> 00:11:09.279
by sending different language objects to
it.

00:11:09.279 --> 00:11:10.880
The language objects themselves are

00:11:10.880 --> 00:11:14.079
loaded from shared libraries.

00:11:14.079 --> 00:11:16.079
Since tree-sitter-mmode already handles

00:11:16.079 --> 00:11:17.360
the parsing part,

00:11:17.360 --> 00:11:19.440
we will instead focus on the functions

00:11:19.440 --> 00:11:20.800
that inspect nodes,

00:11:20.800 --> 00:11:25.279
and in the resulting path tree,

00:11:25.279 --> 00:11:27.030
we can ask tree-sitter what is

00:11:27.030 --> 00:11:44.240
the syntax node at point.

00:11:44.240 --> 00:11:48.480
This is an opaque object, so this is not
very useful.

00:11:48.480 --> 00:12:03.760
We can instead ask what is its type.

00:12:03.760 --> 00:12:08.959
So its type is the symbol comparison
operator.

00:12:08.959 --> 00:12:11.600
In tree-sitter, there are two kinds of nodes,

00:12:11.600 --> 00:12:13.680
anonymous nodes and named nodes.

00:12:13.680 --> 00:12:17.040
Anonymous nodes correspond to simple
grammar elements

00:12:17.040 --> 00:12:21.279
like keywords, operators, punctuations,
and so on.

00:12:21.279 --> 00:12:24.656
Name nodes, on the other hand, are
grammar elements

00:12:24.656 --> 00:12:26.639
that are interesting enough
on their own

00:12:26.639 --> 00:12:30.029
to have a name, like an identifier,

00:12:30.029 --> 00:12:35.440
an expression, or a function definition.

00:12:35.440 --> 00:12:37.323
Name node types are symbols,

00:12:37.323 --> 00:12:42.639
while anonymous node types are strings.

00:12:42.639 --> 00:12:49.760
For example, if we are on this
comparison operator,

00:12:49.760 --> 00:12:55.920
the node type should be a string.

00:12:55.920 --> 00:12:58.959
We can also get other information about
the node.

00:12:58.959 --> 00:13:09.680
For example: what is this text,

00:13:09.680 --> 00:13:20.800
or where it is in the buffer,

00:13:20.800 --> 00:13:43.199
or what is its parent.

00:13:43.199 --> 00:13:46.106
There are many other APIs to query

00:13:46.106 --> 00:13:52.639
our node's properties.

00:13:52.639 --> 00:13:54.234
tree-sitter allows searching

00:13:54.234 --> 00:13:58.240
for structural patterns
within a parse tree.

00:13:58.240 --> 00:14:01.440
It does so through a Lisp-like language.

00:14:01.440 --> 00:14:04.639
This language supports matching
by node types,

00:14:04.639 --> 00:14:07.760
field names, and predicates.

00:14:07.760 --> 00:14:12.639
It also allows capturing nodes for
further processing.

00:14:12.639 --> 00:14:37.680
Let's try to see some examples.

00:14:37.680 --> 00:14:40.206
So in this very simple query,

00:14:40.206 --> 00:14:49.040
we just try to highlight all the
identifiers in the buffer.

00:14:49.040 --> 00:14:53.120
This s side tells tree-sitter
to capture a node.

00:14:53.120 --> 00:14:55.507
In the context of the query builder,

00:14:55.507 --> 00:14:57.360
it's not very important,

00:14:57.360 --> 00:14:59.706
but in normal highlighting query,

00:14:59.706 --> 00:15:01.760
this will determine

00:15:01.760 --> 00:15:06.639
the face used to highlight the note.

00:15:06.639 --> 00:15:08.256
Suppose we want to capture

00:15:08.256 --> 00:15:10.320
all the function names,

00:15:10.320 --> 00:15:13.519
instead of just any identifier.

00:15:13.519 --> 00:15:29.440
You can improve the query like this.

00:15:29.440 --> 00:15:32.639
This will highlight the whole definition.

00:15:32.639 --> 00:15:36.399
But we only want to capture
the function name,

00:15:36.399 --> 00:15:41.054
which means the identifier here.

00:15:41.054 --> 00:15:49.600
So we move the capture to after the
identifier node.

00:15:49.600 --> 00:15:52.959
If we want to capture the
class names as well,

00:15:52.959 --> 00:16:10.079
we just add another pattern.

00:16:10.079 --> 00:16:20.320
Let's look at a more practical example.

00:16:20.320 --> 00:16:23.468
Here we can see that
single-quoted strings

00:16:23.468 --> 00:16:27.279
and double-quoted strings are
highlighted the same.

00:16:27.279 --> 00:16:30.399
But in some places,

00:16:30.399 --> 00:16:33.440
because of some coding conventions,

00:16:33.440 --> 00:16:36.373
it may be desirable to highlight them
differently.

00:16:36.373 --> 00:16:39.073
For example, if the string is
single-quoted,

00:16:39.073 --> 00:16:44.399
we may want to highlight it as a
constant.

00:16:44.399 --> 00:16:46.160
Let's try to see whether we can

00:16:46.160 --> 00:16:56.240
distinguish these two cases.

00:16:56.240 --> 00:17:00.639
So here we get all the strings.

00:17:00.639 --> 00:17:04.079
If we want to see if it's single quotes

00:17:04.079 --> 00:17:08.799
or double quote strings,

00:17:08.799 --> 00:17:13.436
we can try looking at the first
character of the string--

00:17:13.436 --> 00:17:16.720
I mean the first character of the node--

00:17:16.720 --> 00:17:33.600
to check whether it's a single quote or
a double quote.

00:17:33.600 --> 00:17:38.920
So for that, we use tree-sitter's
support for predicates.

00:17:38.920 --> 00:17:43.360
In this case, we use a match predicate

00:17:43.360 --> 00:17:47.339
to check whether the string--
whether the node starts

00:17:47.339 --> 00:17:49.556
with a single quote.

00:17:49.556 --> 00:17:51.280
And with this pattern,

00:17:51.280 --> 00:18:00.400
we only capture the single-quotes
strings.

00:18:00.400 --> 00:18:03.760
Let's try to give it a different face.

00:18:03.760 --> 00:18:13.039
So we copy the pattern,

00:18:13.039 --> 00:18:25.120
and we add this pattern for Python only.

00:18:25.120 --> 00:18:31.440
But we also want to give the capture
a different name.

00:18:31.440 --> 00:18:46.559
Let's say we want to highlight it
as a keyword.

00:18:46.559 --> 00:19:06.320
And now, if we refresh the buffer,

00:19:06.320 --> 00:19:08.523
we see that single quote strings

00:19:08.523 --> 00:19:14.400
are highlighted as keywords.

00:19:14.400 --> 00:19:15.751
The highlighting patterns

00:19:15.751 --> 00:19:19.200
can also be set for a single project

00:19:19.200 --> 00:19:23.440
using directory-local variables.

00:19:23.440 --> 00:19:35.760
For example, let's take a look at
Emacs's source code.

00:19:35.760 --> 00:19:41.123
So in Emacs's C source,
there are a lot of uses

00:19:41.123 --> 00:19:43.760
of these different macros

00:19:43.760 --> 00:19:47.679
to define functions,

00:19:47.679 --> 00:19:53.256
and you can see this is actually
the function name,

00:19:53.256 --> 00:19:56.373
but it's highlighted as the string.

00:19:56.373 --> 00:20:03.679
So what we want is to somehow
recognize this pattern

00:20:03.679 --> 00:20:07.600
and highlight it.

00:20:07.600 --> 00:20:11.280
Highlight this part

00:20:11.280 --> 00:20:14.559
with the function face instead.

00:20:14.559 --> 00:20:17.679
In order to do that,

00:20:17.679 --> 00:20:31.760
we put a pattern in this project's
directory-local settings file.

00:20:31.760 --> 00:20:40.159
So we can put this button in
the C mode section.

00:20:40.159 --> 00:20:48.000
And now, if we enable tree-sitter,

00:20:48.000 --> 00:20:50.480
you can see that this is highlighted

00:20:53.200 --> 00:20:55.056
as a normal function definition.

00:20:55.056 --> 00:21:01.200
So this is the function face
like we wanted.

00:21:01.200 --> 00:21:07.200
The pattern for this is
actually pretty simple.

00:21:07.200 --> 00:21:12.373
It's only this part.

00:21:12.373 --> 00:21:16.456
So if it's a function call

00:21:16.456 --> 00:21:19.679
where the name of the function is
defun,

00:21:19.679 --> 00:21:24.240
then we highlight the defun as a
keyword,

00:21:24.240 --> 00:21:26.923
and then the first string element,

00:21:26.923 --> 00:21:35.360
we highlight it as a function name.

00:21:35.360 --> 00:21:39.280
Since the language objects are actually
native code,

00:21:39.280 --> 00:21:41.459
they have to be compiled
for each platform

00:21:41.459 --> 00:21:43.440
that we want to support.

00:21:43.440 --> 00:21:48.159
This will become a big obstacle for
tree-sitter adoption.

00:21:48.159 --> 00:21:52.960
Therefore, I've created a language bundle
package, tree-sitter-langs,

00:21:52.960 --> 00:21:55.773
that takes care of pre-compiling the
grammars,

00:21:55.773 --> 00:22:01.600
the most common grammars for all three
major platforms.

00:22:01.600 --> 00:22:05.360
It also takes care of distributing
these binaries

00:22:05.360 --> 00:22:08.080
and provides some highlighting queries

00:22:08.080 --> 00:22:11.440
for some of the languages.

00:22:11.440 --> 00:22:13.760
It should be noted that this package

00:22:13.760 --> 00:22:19.919
should be treated as a temporary
distribution mechanism only,

00:22:19.919 --> 00:22:24.720
to help with bootstrapping
tree-sitter adoption.

00:22:24.720 --> 00:22:27.760
The plan is that eventually these files

00:22:27.760 --> 00:22:29.156
should be provided by

00:22:29.156 --> 00:22:32.480
the language major modes themselves.

00:22:32.480 --> 00:22:36.320
But in order to do that, we need better
tooling,

00:22:36.320 --> 00:22:40.240
so we're not there yet.

00:22:40.240 --> 00:22:43.280
Since the core already works
reasonably well,

00:22:43.280 --> 00:22:45.289
there are several areas
that would benefit

00:22:45.289 --> 00:22:49.120
from the community's contribution.

00:22:49.120 --> 00:22:52.640
So tree-sitter's upstream language
repositories

00:22:52.640 --> 00:22:55.679
already contain highlighting queries on
their own.

00:22:55.679 --> 00:22:57.573
However, they are pretty basic,

00:22:57.573 --> 00:23:02.559
and they may not fit well with existing
Emacs conventions.

00:23:02.559 --> 00:23:07.120
Therefore, the language bundle has its
own set of highlighting queries.

00:23:07.120 --> 00:23:12.556
This requires maintenance until language
major modes adopt tree-sitter

00:23:12.556 --> 00:23:16.640
and maintain the queries on their own.

00:23:16.640 --> 00:23:19.056
The queries are actually
quite easy to write,

00:23:19.056 --> 00:23:22.000
as you've already seen.

00:23:22.000 --> 00:23:25.360
You just need to be familiar
with the language,

00:23:25.360 --> 00:23:35.200
familiar enough to come up with sensible
highlighting patterns.

00:23:35.200 --> 00:23:39.679
And if you are a maintainer of a
language major mode,

00:23:39.679 --> 00:23:44.189
you may want to consider integrating
tree-sitter into your mode,

00:23:44.189 --> 00:23:48.573
initially maybe as an optional feature.

00:23:48.573 --> 00:23:53.279
The integration is actually pretty
straightforward,

00:23:53.279 --> 00:23:56.640
especially for syntax highlighting.

00:23:56.640 --> 00:24:01.520
Or alternatively,

00:24:01.520 --> 00:24:05.760
you can also try writing a new major
mode from scratch

00:24:05.760 --> 00:24:08.000
that relies on tree-sitter

00:24:08.000 --> 00:24:12.559
from the very beginning.

00:24:12.559 --> 00:24:17.523
The code for such a major mode is
quite simple.

00:24:17.523 --> 00:24:23.200
For example, this is the proposed

00:24:23.200 --> 00:24:26.240
wat-mode for web assembly.

00:24:26.240 --> 00:24:39.520
The code is just one page of code,
not a lot.

00:24:39.520 --> 00:24:42.720
You can also try writing new minor modes

00:24:42.720 --> 00:24:46.559
or writing integration packages.

00:24:46.559 --> 00:24:50.880
For example, a lot of packages

00:24:50.880 --> 00:24:54.559
may benefit from tree-sitter integration,

00:24:54.559 --> 00:25:02.960
but no one has written
the integration yet.

00:25:02.960 --> 00:25:04.836
If you are interested in tree-sitter,

00:25:04.836 --> 00:25:08.023
you can use these links to learn more
about it.

00:25:08.023 --> 00:25:11.440
I think that's it for me today.

00:25:11.440 --> 00:25:18.159
I'm happy to answer any questions.