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+WEBVTT captioned by sachac
+
+00:00:00.000 --> 00:00:03.240
+Hey everyone, my name is Abin Simon
+
+00:00:03.240 --> 00:00:05.080
+and this talk is about "Tree-sitter:
+
+00:00:05.080 --> 00:00:08.200
+Beyond Syntax Highlighting."
+
+00:00:08.200 --> 00:00:10.720
+For those who are not aware of what Tree-sitter is,
+
+00:00:10.720 --> 00:00:11.720
+let me give you a quick intro.
+
+00:00:11.720 --> 00:00:17.120
+Tree-sitter, at its core, is a parser generator tool
+
+00:00:17.120 --> 00:00:19.440
+and an incremental parsing library.
+
+00:00:19.440 --> 00:00:22.000
+What it essentially means is that it gives you
+
+00:00:22.000 --> 00:00:23.154
+an always up-to-date
+
+00:00:23.155 --> 00:00:24.200
+AST [abstract syntax tree] of your code.
+
+00:00:24.200 --> 00:00:27.960
+In the current Emacs frame, what you see to the right
+
+00:00:27.960 --> 00:00:30.840
+is the AST tree produced by Tree-sitter
+
+00:00:30.840 --> 00:00:33.560
+of the code that is on the left.
+
+00:00:33.560 --> 00:00:37.000
+For example, if you go to this "if" statement,
+
+00:00:37.000 --> 00:00:38.840
+you can see it goes here.
+
+00:00:38.840 --> 00:00:41.440
+It is also really good at handling errors.
+
+00:00:41.440 --> 00:00:44.400
+For example, if I were to delete this [if statement],
+
+00:00:44.400 --> 00:00:47.960
+it still parses out a tree as much as it can,
+
+00:00:47.960 --> 00:00:50.280
+but with an error node.
+
+00:00:50.280 --> 00:00:51.760
+Now let's see how we can query the tree
+
+00:00:51.760 --> 00:00:54.440
+to get the information that we need.
+
+00:00:54.440 --> 00:01:01.480
+Let's first try to get all the identifiers in the buffer.
+
+00:01:01.480 --> 00:01:04.000
+It highlights all the identifiers in the buffer,
+
+00:01:04.000 --> 00:01:05.440
+but let's say we want to get something
+
+00:01:05.440 --> 00:01:07.280
+a little more precise.
+
+00:01:07.280 --> 00:01:10.400
+Let's say we wanted to get this "i" here.
+
+00:01:10.400 --> 00:01:13.280
+This, in our case, would be this identifier
+
+00:01:13.280 --> 00:01:15.200
+inside this assignment expression
+
+00:01:15.200 --> 00:01:27.320
+inside this "for" statement.
+
+00:01:27.320 --> 00:01:29.920
+We can write it out like this.
+
+00:01:29.920 --> 00:01:31.880
+I hope this gives you a basic idea
+
+00:01:31.880 --> 00:01:34.480
+of how Tree-sitter works and how you can query
+
+00:01:34.480 --> 00:01:37.040
+to get the information that you need.
+
+00:01:37.040 --> 00:01:39.520
+First of all, let's see how Tree-sitter can help us
+
+00:01:39.520 --> 00:01:41.880
+with syntax highlighting.
+
+00:01:41.880 --> 00:01:46.480
+This is the default syntax highlighting by Emacs for SQL.
+
+00:01:46.480 --> 00:01:52.000
+Now let's see how Tree-sitter helps.
+
+00:01:52.000 --> 00:01:54.240
+This is the syntax highlighting in Emacs
+
+00:01:54.240 --> 00:01:56.760
+which Tree-sitter enabled.
+
+00:01:56.760 --> 00:01:58.240
+You'll see that we're able to target
+
+00:01:58.240 --> 00:02:01.240
+a lot more things and highlight them.
+
+00:02:01.240 --> 00:02:03.138
+That said, you don't always have to
+
+00:02:03.139 --> 00:02:04.200
+highlight everything.
+
+00:02:04.200 --> 00:02:15.640
+I personally prefer a much simpler theme.
+
+00:02:15.640 --> 00:02:17.880
+Now let's see how Tree-sitter helps you simplify
+
+00:02:17.880 --> 00:02:20.920
+adding custom syntax highlighting to your code.
+
+00:02:20.920 --> 00:02:22.200
+This is a Python file which has
+
+00:02:22.200 --> 00:02:25.640
+a class and a few member functions.
+
+00:02:25.640 --> 00:02:27.680
+Anyone who has used Python will know that
+
+00:02:27.680 --> 00:02:32.040
+the "self" keyword, while it is passed in as an argument,
+
+00:02:32.040 --> 00:02:34.240
+it has more meaning than that.
+
+00:02:34.240 --> 00:02:35.480
+Let's see if you can use Tree-sitter
+
+00:02:35.480 --> 00:02:38.720
+to highlight just the "self" keyword.
+
+00:02:38.720 --> 00:02:40.400
+If you look at the Tree-sitter tree,
+
+00:02:40.400 --> 00:02:43.120
+you can see that this is the first identifier
+
+00:02:43.120 --> 00:02:45.520
+in the list of parameters for a function definition.
+
+00:02:45.520 --> 00:02:55.480
+This is how you would query for the first identifier
+
+00:02:55.480 --> 00:02:59.320
+inside parameters inside a function definition.
+
+00:02:59.320 --> 00:03:02.520
+Now, if you see here, it also matches "cls",
+
+00:03:02.520 --> 00:03:11.360
+but let's restrict it to match just "self".
+
+00:03:11.360 --> 00:03:14.200
+Now we have a Tree-sitter query that identifies
+
+00:03:14.200 --> 00:03:16.960
+the first argument to the function definition
+
+00:03:16.960 --> 00:03:19.640
+and is also called "self".
+
+00:03:19.640 --> 00:03:22.520
+We can use this to apply custom highlighting onto this.
+
+00:03:22.520 --> 00:03:25.000
+This is pretty much all the code
+
+00:03:25.000 --> 00:03:26.520
+that you'll need to do this.
+
+00:03:26.520 --> 00:03:29.240
+The first block here is essentially to say to
+
+00:03:29.240 --> 00:03:32.160
+Tree-sitter to highlight anything with python.self
+
+00:03:32.160 --> 00:03:35.720
+with the face of custom-set.
+
+00:03:35.720 --> 00:03:37.520
+Now the second block here essentially is
+
+00:03:37.520 --> 00:03:39.800
+how we match for that.
+
+00:03:39.800 --> 00:03:41.800
+Now if you go back into a Python buffer
+
+00:03:41.800 --> 00:03:44.680
+and re-enable python-mode, we'll see that "self"
+
+00:03:44.680 --> 00:03:47.120
+is highlighted differently.
+
+00:03:47.120 --> 00:03:48.880
+How about creating text objects?
+
+00:03:48.880 --> 00:03:50.440
+Tree-sitter can help there too.
+
+00:03:50.440 --> 00:03:53.080
+For those who don't know, text objects
+
+00:03:53.080 --> 00:03:54.440
+is an idea that comes from Vim,
+
+00:03:54.440 --> 00:03:57.760
+and you can do things like select word,
+
+00:03:57.760 --> 00:04:00.520
+delete word, things like that.
+
+00:04:00.520 --> 00:04:06.200
+There are other text objects like line and paragraph.
+
+00:04:06.200 --> 00:04:09.000
+For each text object, you can have operations
+
+00:04:09.000 --> 00:04:09.760
+that are defined on them.
+
+00:04:09.760 --> 00:04:13.600
+For example, delete, copy, select, comment,
+
+00:04:13.600 --> 00:04:16.400
+all of these are operations that you can do.
+
+00:04:16.400 --> 00:04:19.400
+Let's try and use Tree-sitter to add more text objects.
+
+00:04:19.400 --> 00:04:20.560
+This is a plugin that I wrote
+
+00:04:20.560 --> 00:04:25.000
+which lets you add more text objects into Emacs.
+
+00:04:25.000 --> 00:04:27.880
+It helps you code aware text objects
+
+00:04:27.880 --> 00:04:31.880
+like functions, conditionals, loops, and such.
+
+00:04:31.880 --> 00:04:34.360
+Let's see an example scenario of how
+
+00:04:34.360 --> 00:04:35.920
+something like this could come in handy.
+
+00:04:35.920 --> 00:04:39.280
+For example, I can select inside this condition
+
+00:04:39.280 --> 00:04:42.960
+or inside this function and do things like that.
+
+00:04:42.960 --> 00:04:44.520
+Let's say I want to take this conditional,
+
+00:04:44.520 --> 00:04:47.160
+move to the next function, and create it here.
+
+00:04:47.160 --> 00:04:49.640
+What I would do is something like
+
+00:04:49.640 --> 00:04:52.320
+delete the conditional, move to the next function,
+
+00:04:52.320 --> 00:04:56.240
+create a conditional there, and paste.
+
+00:04:56.240 --> 00:04:57.160
+Let's try another example.
+
+00:04:57.160 --> 00:05:01.360
+Let's say I want to take this and move it to the end.
+
+00:05:01.360 --> 00:05:02.960
+If I had to do it without text objects,
+
+00:05:02.960 --> 00:05:06.800
+I'd probably have to go back to the previous comma,
+
+00:05:06.800 --> 00:05:10.440
+delete till next comma, find the closing bracket,
+
+00:05:10.440 --> 00:05:11.880
+and paste before.
+
+00:05:11.880 --> 00:05:14.040
+That works, but let's see
+
+00:05:14.040 --> 00:05:16.520
+how Tree-sitter can simplify it.
+
+00:05:16.520 --> 00:05:19.240
+With Tree-sitter, I can say delete the argument,
+
+00:05:19.240 --> 00:05:22.880
+go to the end of the next argument, and then paste.
+
+00:05:22.880 --> 00:05:25.280
+Tree-sitter essentially helps Emacs
+
+00:05:25.280 --> 00:05:27.240
+understand the code better semantically.
+
+00:05:27.240 --> 00:05:29.600
+Here is yet another use case.
+
+00:05:29.600 --> 00:05:31.480
+I work at a remote company,
+
+00:05:31.480 --> 00:05:33.440
+and I often find myself being in a call
+
+00:05:33.440 --> 00:05:35.400
+with my teammates, explaining the code to them.
+
+00:05:35.400 --> 00:05:38.000
+And one thing that really comes in handy
+
+00:05:38.000 --> 00:05:39.760
+is the narrowing capability of Emacs.
+
+00:05:39.760 --> 00:05:43.040
+Specifically, the fancy-narrow package.
+
+00:05:43.040 --> 00:05:44.840
+I use it to narrow just the function,
+
+00:05:44.840 --> 00:05:48.760
+or I could narrow to the conditional.
+
+00:05:48.760 --> 00:05:51.520
+Next to the end, the list would be code folding.
+
+00:05:51.520 --> 00:05:54.480
+This is a package which uses Tree-sitter
+
+00:05:54.480 --> 00:05:57.560
+to improve the code folding functionalities of Emacs.
+
+00:05:57.560 --> 00:06:00.200
+Code folding has always been this thing
+
+00:06:00.200 --> 00:06:02.280
+that I've had a love-hate relationship with.
+
+00:06:02.280 --> 00:06:04.280
+It usually works most of the time,
+
+00:06:04.280 --> 00:06:06.960
+but then fails if the indentation is wrong
+
+00:06:06.960 --> 00:06:09.160
+or we do something weird with the arguments.
+
+00:06:09.160 --> 00:06:11.680
+But now with Tree-sitter in the mix,
+
+00:06:11.680 --> 00:06:12.720
+it's a lot more precise.
+
+00:06:12.720 --> 00:06:17.040
+I can fold comments, I can fold functions,
+
+00:06:17.040 --> 00:06:20.480
+I can fold conditionals. You get the idea.
+
+00:06:20.480 --> 00:06:23.840
+I work with Kubernetes, which means I end up
+
+00:06:23.840 --> 00:06:28.080
+having to write and read a lot of YAML files.
+
+00:06:28.080 --> 00:06:31.840
+And navigating big YAML files is a mess.
+
+00:06:31.840 --> 00:06:35.760
+The two main problems are figuring out where I am,
+
+00:06:35.760 --> 00:06:38.760
+and two, navigating to where I want to be.
+
+00:06:38.760 --> 00:06:41.760
+Let's see how Tree-sitter can help us with both of this.
+
+00:06:41.760 --> 00:06:43.840
+This is an example YAML file.
+
+00:06:43.840 --> 00:06:47.080
+To be precise, this is the values file
+
+00:06:47.080 --> 00:06:48.640
+of the Redis helm chart.
+
+00:06:48.640 --> 00:06:52.240
+I'm somewhere in the file on tag under image,
+
+00:06:52.240 --> 00:06:54.880
+but I don't know what this tag is for.
+
+00:06:54.880 --> 00:06:57.240
+But with the help of Tree-sitter,
+
+00:06:57.240 --> 00:06:59.160
+I've been able to add this information
+
+00:06:59.160 --> 00:07:00.440
+into my header line.
+
+00:07:00.440 --> 00:07:02.960
+If you see in the header line,
+
+00:07:02.960 --> 00:07:05.880
+you'll see that I'm under sentinel.image.
+
+00:07:05.880 --> 00:07:08.800
+Now let's see how this helps with navigation.
+
+00:07:08.800 --> 00:07:12.680
+Let's say I want to enable persistence on master node.
+
+00:07:12.680 --> 00:07:18.200
+So with the help of Tree-sitter,
+
+00:07:18.200 --> 00:07:20.400
+I was able to enumerate every field
+
+00:07:20.400 --> 00:07:22.200
+that is available in this YAML file,
+
+00:07:22.200 --> 00:07:24.520
+and I can pass that information onto imenu,
+
+00:07:24.520 --> 00:07:28.040
+which I can then use to go to exactly where I want to.
+
+00:07:28.040 --> 00:07:30.000
+Also, since we're not dealing with
+
+00:07:30.000 --> 00:07:32.600
+any language specific constructs,
+
+00:07:32.600 --> 00:07:34.040
+this is very easy to extend to
+
+00:07:34.040 --> 00:07:35.760
+other similar languages
+
+00:07:35.760 --> 00:07:37.440
+or config files in this case.
+
+00:07:37.440 --> 00:07:39.520
+So for example, this is a JSON file,
+
+00:07:39.520 --> 00:07:44.800
+and I can navigate to location or project.
+
+00:07:44.800 --> 00:07:48.320
+And just like in YAML, it shows me where I'm at.
+
+00:07:48.320 --> 00:07:49.920
+I'm in projects.name,
+
+00:07:49.920 --> 00:07:52.880
+or I'm inside projects.highlights.
+
+00:07:52.880 --> 00:07:55.600
+Or how about Nix?
+
+00:07:55.600 --> 00:07:57.480
+This is my home.nix file.
+
+00:07:57.480 --> 00:08:01.040
+Again, I can search for services,
+
+00:08:01.040 --> 00:08:04.640
+and this lists me all the services that I've enabled.
+
+00:08:04.640 --> 00:08:06.720
+How about just services.description?
+
+00:08:06.720 --> 00:08:08.160
+So this is all the services
+
+00:08:08.160 --> 00:08:10.480
+that I've enabled and have descriptions.
+
+00:08:10.480 --> 00:08:12.720
+Now that we have seen this for config files,
+
+00:08:12.720 --> 00:08:15.040
+let's see how similar things apply for code.
+
+00:08:15.040 --> 00:08:16.760
+Just like in config files,
+
+00:08:16.760 --> 00:08:18.680
+I can see which function I'm under,
+
+00:08:18.680 --> 00:08:21.560
+and if I go to the next function, it changes.
+
+00:08:21.560 --> 00:08:23.960
+Okay, here is something really awesome.
+
+00:08:23.960 --> 00:08:26.600
+This is probably one of my favorites,
+
+00:08:26.600 --> 00:08:30.400
+and one of the things that actually made me understand
+
+00:08:30.400 --> 00:08:34.080
+how powerful Tree-sitter is, and got me into it.
+
+00:08:34.080 --> 00:08:35.680
+I work with a lot of Go code,
+
+00:08:35.680 --> 00:08:38.840
+and anyone who has worked with Go will tell you
+
+00:08:38.840 --> 00:08:41.040
+how repetitive it is handling errors.
+
+00:08:41.040 --> 00:08:42.800
+For those who don't write Go,
+
+00:08:42.800 --> 00:08:45.200
+let me give you a rough idea of what I'm talking about.
+
+00:08:45.200 --> 00:08:47.000
+If you want to bubble up the error,
+
+00:08:47.000 --> 00:08:49.920
+the way you would do it is just to return the error
+
+00:08:49.920 --> 00:08:51.400
+to the function that called it.
+
+00:08:51.400 --> 00:08:55.720
+Over here, you can either return nil or an empty value,
+
+00:08:55.720 --> 00:08:57.640
+and at the end, you return error.
+
+00:08:57.640 --> 00:09:00.200
+Let's try and use Tree-sitter to do this.
+
+00:09:00.200 --> 00:09:03.120
+Using the help of Tree-sitter, let's make Emacs
+
+00:09:03.120 --> 00:09:06.421
+go back, figure out what the return arguments are,
+
+00:09:06.422 --> 00:09:08.240
+figure out what their default values are,
+
+00:09:08.240 --> 00:09:11.480
+and automatically fill in the return statement.
+
+00:09:11.480 --> 00:09:13.040
+It would look something like this.
+
+00:09:13.040 --> 00:09:16.120
+In my case, it filled in the complete form,
+
+00:09:16.120 --> 00:09:18.320
+it figured out what the return arguments are,
+
+00:09:18.320 --> 00:09:19.320
+what their types are,
+
+00:09:19.320 --> 00:09:20.960
+and what their default values are,
+
+00:09:20.960 --> 00:09:22.800
+and filled out the entire return.
+
+00:09:22.800 --> 00:09:24.760
+And since this is a template,
+
+00:09:24.760 --> 00:09:27.720
+I can go to the next function, do the same thing,
+
+00:09:27.720 --> 00:09:29.560
+next function, do the same thing,
+
+00:09:29.560 --> 00:09:31.520
+next function, do the same thing.
+
+00:09:31.520 --> 00:09:34.360
+Here is a really fascinating use case of Tree-sitter,
+
+00:09:34.360 --> 00:09:36.320
+structural editing.
+
+00:09:36.320 --> 00:09:38.200
+You might be aware of plugins like paredit,
+
+00:09:38.200 --> 00:09:40.280
+which seems to "know" your code.
+
+00:09:40.280 --> 00:09:42.520
+This sort of takes it onto another level.
+
+00:09:42.520 --> 00:09:46.040
+It is in its early stages, but what this lets you do
+
+00:09:46.040 --> 00:09:48.920
+is completely treat your code as an AST,
+
+00:09:48.920 --> 00:09:52.000
+and edit as if it's a tree instead of characters.
+
+00:09:52.000 --> 00:09:54.640
+I am not going to go much in depth into it,
+
+00:09:54.640 --> 00:09:57.000
+but if you're interested, there is a talk
+
+00:09:57.000 --> 00:09:59.080
+from last year's EmacsConf around it.
+
+00:09:59.080 --> 00:10:02.320
+I'm just going to end this with one last tiny thing
+
+00:10:02.320 --> 00:10:04.920
+that I found in the tree-sitter-extras package.
+
+00:10:04.920 --> 00:10:07.600
+It's this tiny macro called tree-sitter-save-excursion.
+
+00:10:07.600 --> 00:10:11.240
+It works pretty much like save-excursion, but better.
+
+00:10:11.240 --> 00:10:13.400
+It uses the Tree-sitter syntax tree
+
+00:10:13.400 --> 00:10:14.800
+instead of just the code
+
+00:10:14.800 --> 00:10:16.720
+to figure out where to restore the position.
+
+00:10:16.720 --> 00:10:20.200
+My main use case for this was with code formatters.
+
+00:10:20.200 --> 00:10:22.080
+Since the code moves around a lot
+
+00:10:22.080 --> 00:10:23.160
+when it gets formatted,
+
+00:10:23.160 --> 00:10:25.000
+save-excursion was completely useless,
+
+00:10:25.000 --> 00:10:26.240
+but this came in handy.
+
+00:10:26.240 --> 00:10:28.120
+I'll just leave you off with
+
+00:10:28.120 --> 00:10:31.120
+what the future of Tree-sitter looks like for Emacs.
+
+00:10:31.120 --> 00:10:33.760
+So far, every Tree-sitter related feature
+
+00:10:33.760 --> 00:10:36.040
+that I've talked about is powered by this library.
+
+00:10:36.040 --> 00:10:42.320
+But there is talk about Tree-sitter coming into the core.
+
+00:10:42.320 --> 00:10:45.840
+It will most probably be landing in Emacs 29,
+
+00:10:45.840 --> 00:10:48.720
+and if you want to check out the work on Tree-sitter
+
+00:10:48.720 --> 00:10:51.200
+in core Emacs, you can check out
+
+00:10:51.200 --> 00:10:52.920
+the features/tree-sitter branch.
+
+00:10:52.920 --> 00:10:56.640
+You'll probably see more and more features and packages
+
+00:10:56.640 --> 00:10:59.640
+relying upon Tree-sitter, and even major modes
+
+00:10:59.640 --> 00:11:01.560
+being powered by Tree-sitter.
+
+00:11:01.560 --> 00:11:03.880
+And that's a wrap from me. Thank you.