path: root/2021/captions/emacsconf-2021-test--test-blocks--eduardo-ochs--main.vtt

WEBVTT

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Hi! My name is Eduardo Ochs. 

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I'm the author of 

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an Emacs package called eev, 

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and this talk is about 

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a new feature of eev 

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called "test blocks".

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Let's start by a demo.

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This is a file in Lua that defines 

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these two functions here,

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and if we type <f8> several times here,

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the <f8>s create a Lua REPL here

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and then they send these lines 

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to the REPL, where this line here

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loads this file into the REPL, 

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and these other lines here

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are tests for these lines.

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There's a lot of information here, 

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so let me organize them

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in a more visual way.

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This is our file in Lua.

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Lua sees this thing 

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as a multi-line comment, 

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but we are going to see it 

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as a test block. 

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And eev mode is active, 

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so <f8> does the right thing.

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These three lines here 

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set up the target buffer 

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running a Lua REPL. 

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You can see the the prompt 

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of the REPL here,

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and these lines here 

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are sent to the REPL.

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When we type <f8> 

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on a line that starts

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with a red star, 

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like these lines here,

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what <f8> does is that 

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it sends the rest of the line--

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sorry, it executes 

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the rest of the line as Lisp.

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So the three <f8>s here

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executes these lines as Lisp, 

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and they set up the target buffer here.

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When we type <f8> 

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on a line that does not start

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with a red star, 

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the <f8> sends the line 

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to the target buffer and moves down.

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This line loads this file 

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in the REPL, and these lines are tests.

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So we just saw how to use

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an existing test block; 

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let's now see how to create 

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a new test block. 

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We just have to run this:

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M-x ee-insert-test-block -

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or M-x eeit.

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The result depends on the major mode.

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Let's understand that

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by looking at the source code.

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eeit is an alias to this function here,

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and this function is just

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five lines of code plus a docstring...

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and the docstring explains 

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that if the major mode is foo-mode,

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then this function tries to call

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a function called ee-insert-test-foo-mode

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if that function exists,

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and that, if that function does not exist,

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then it yields an error.

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And here's an example 

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of one such function. 

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That's a function that inserts 

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a test block in haskell-mode.

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Here we can see two functions like this:

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one for haskell-mode and one for js-mode.

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These functions look quite similar, 

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but their effects look quite different.

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To make this comparison here, 

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I started by writing--

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by creating seven files, 

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each one in a different language.

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Initially, each one of these files

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only had a comment 

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with the name of the language... 

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so: C, Haskell, Javascript, Org Mode, etc.

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In each one of these files, 

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I typed M-x eeit to insert a test block.

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So here we can see that

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these test blocks are different.

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For example, the syntax 

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for multi-line comments

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is different depending on the language.

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This block here that selects

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which REPL to run is also different, 

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and this line here that tells the REPL

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to load the current file

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is also different,

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depending on the language.

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In some cases, I had to improvise a bit.

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For example, to implement test blocks

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in shell mode, I had to use

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this weird syntax using a here-document.

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In Tcl, I also had to improvise a bit, 

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and in some cases,

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I had to improvise a lot.

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For example, in Org Mode,

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there isn't an obvious REPL to run, 

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and there isn't an obvious way

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to load the the current Org file

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into the REPL, so the default action

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of M-x eeit in Org Mode

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is just to insert this thing here,

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that we can use to run a shell in a REPL.

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So these functions are quite similar.

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In the beginning, 

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I was writing all of them by hand... 

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but then I got bored 

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and I wrote a function

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to help me write functions like that.

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This function is called find-eeit-links,

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and it creates a temporary buffer,

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and the contents of this temporary buffer

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depends on the major mode. For example, 

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if the current mode is python-mode,

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then running this function here

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creates a temporary buffer 

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that lets me write the support 

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for test blocks in python-mode, 

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or rewrite the function 

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that supports test blocks

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in python-mode.

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So if I'm in python-mode and I run this,

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I get a temporary buffer like this,

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in which this thing is my template 

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for the function. Usually, this string 

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is totally wrong, 

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I have to rewrite this string,

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but the rest is right. 

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You can see python-mode here

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in the name of the function. 

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So we have to edit this 

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and save that to our ~/.emacs.

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By the way, these things here 

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hyperlinks to many different things...

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This Elisp hyperlink here

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points to the source code, 

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to the section in which these functions

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are defined. So you can see this here,

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the function that supports C,

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the function for Haskell, 

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the function for Javascript, etc...

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and that's it! 

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This is a five-minute talk,

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so I can't say much...

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If you want more information, 

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or if you want to see real-world examples,

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how I use test blocks, etc. etc., 

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see this page here... 

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and I do not have time to explain this

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"By the way" here.

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So that's it! Thanks! =)

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[captions by Eduardo Ochs]