Vimscript's basic syntax is highlighted

Now that you've removed the stumbling blocks along the way, it's time to start writing some useful code for our Potion plug-in. We'll start with some simple syntax highlights.

Create syntax/potion.vim Put the following code in your file:

if exists("b:current_syntax")
    finish
endif

echom "Our syntax highlighting code will go here."

let b:current_syntax = "potion"

Close Vim and open your factorial.pn file. Y ou may or may not be able to see the message, depending on whether you have other plug-ins that output the message after the plug-in. If you :message you will see that the file is indeed loaded.

Note: Every time I tell you to open a Potion file, I want you to open it in a new Vim window or process, not in a split or tab. Opening a new Vim window causes Vim to reload all your plug-ins for this purpose, and opening a split does not.

The lines at the beginning and end of the code file are a common practice, and if the syntax highlight of this buffer has been started, there is no need to reload.

Highlight keywords

For the rest of this chapter, we'll ignore the if and let defense walls if and let of the file. Don't remove those lines, it's just that the eyes are not clear.

Replace the placeholder echom in the file with the echom

syntax keyword potionKeyword to times
highlight link potionKeyword Keyword

Close factorial.pn and reopen it. to and times are highlighted as keyword types in your color scheme!

These two lines show the basic syntax highlights in Vim. To highlight a syntax:

• You first define a syntax keyword or related commands, which we'll mention more than once.
• Then you want to link this set of types to highlight groups. A highlight group is something you define in a color scheme, such as "the function name should be blue."

This allows the plug-in author to decide on meaningful syntax types to group and then link to a common highlight group. This also allows the color scheme creator to decide on a common program structure without having to consider a separate language.

In addition to what we use in our toy program, Potion has other keywords, so let's modify the syntax files to highlight them together.

syntax keyword potionKeyword loop times to while
syntax keyword potionKeyword if elsif else
syntax keyword potionKeyword class return

highlight link potionKeyword Keyword

The first thing to say is that the last line has not been changed. We still tell Vim that all potionKeyword should be highlighted as Keyword

We've now added three new lines, syntax keyword potionKeyword T his means that executing this command multiple times does not reset the syntax type grouping -- it does augment it! This allows you to define groupings in a zero-based way.

How you define grouping depends on you:

• You can write everything in just one line.
• You can divide into rows to meet the rules of 80 columns per row for longer reading.
• You can have one line for each item to make the results of diff clearer.
• You can put the related items on the same line as I did here.

Highlight the function

Another highlight group for Vim is Function T his brings some Potion's built-in functions to our highlighted files. Change your syntax file to this:

syntax keyword potionKeyword loop times to while
syntax keyword potionKeyword if elsif else
syntax keyword potionKeyword class return

syntax keyword potionFunction print join string

highlight link potionKeyword Keyword
highlight link potionFunction Function

Close and reopen the factorial.pn see that the built-in Potion function is now highlighted.

It works just like keyword highlighting. We defined the new syntax type grouping and linked to different highlight groups.

Practice

Think about why if if exists at the beginning of the file and let at the let are useful. I f you don't understand, don't worry. I also asked Tim Pope about it.

Browse :help syn-keyword . Notice the section iskeyword

Read :help iskeyword .

Read :help group-name learn about some of the common highlight groups commonly used by color scheme authors.