A syntax highlighter for Swift code that uses SwiftSyntax. You can use it either from the command-line, via the swift-highlight executable, or in Swift code using the SwiftSyntaxHighlighter module.

This functionality is discussed in the NSHipster article SwiftSyntax.

• Swift 5.3+

The swift-highlight executable can be run from the command line to highlight either a path to a source file or source code:

$ swift highlight 'print("Hello, world!")'
<pre class="highlight"><code><span class="keyword">let</span> <span class="variable">greeting</span> = <span class="string literal">&quot;</span><span class="string literal">Hello, world!</span><span class="string literal">&quot;</span></code></pre>

Pass the --scheme pygments option to generate Pygments-compatible HTML:

$ swift highlight 'print("Hello, world!")' --scheme pygments
<pre class="highlight"><code><span class="n">print</span><span class="p">(</span><span class="p">&quot;</span><span class="s2">Hello, world!</span><span class="p">&quot;</span><span class="p">)</span></code></pre>

swift-highlight also accepts arguments piped from standard input (stdin):

echo 'print("Hello, world!")' | swift highlight
<pre class="highlight"><code><span class="variable">print</span>(<span class="string literal">&quot;</span><span class="string literal">Hello, world!</span><span class="string literal">&quot;</span>)
</code></pre>

Run the following command to install using homebrew:

$ brew install nshipster/formulae/swift-syntax-highlight

Run the following commands to build and install manually:

$ git clone https://github.com/NSHipster/SwiftSyntaxHighlighter.git
$ cd SwiftSyntaxHighlighter
$ make install

SwiftSyntaxHighlighter provides type methods named highlight that take either source code as a String, a source file URL, or a SourceFileSyntax AST created by SwiftSyntax.

import SwiftSyntaxHighlighter

let code = """
print("Hello, world!")
"""

let html = try SwiftSyntaxHighlighter.highlight(source: source, using: Xcode.self)

After running this code, html contains the following string:

<pre class="highlight"><code><span class="keyword">let</span> <span class="variable">greeting</span> = <span class="string literal">&quot;</span><span class="string literal">Hello, world!</span><span class="string literal">&quot;</span></code></pre>

Add the SwiftSyntaxHighlighter package to your target dependencies in Package.swift:

import PackageDescription

let package = Package(
  name: "YourProject",
  dependencies: [
    .package(
        url: "https://github.com/NSHipster/SwiftSyntaxHighlighter",
        from: "1.2.4"
    ),
  ]
)

Then run the swift build command to build your project.

• Xcode cannot run unit tests (⌘U) when opening the SwiftSyntaxHighlighter package directly, as opposed first to generating an Xcode project file with swift package generate-xcodeproj. (The reported error is: Library not loaded: @rpath/lib_InternalSwiftSyntaxParser.dylib). As a workaround, you can install the latest toolchain and enable it in "Xcode > Preferences > Components > Toolchains". Alternatively, you can run unit tests from the command line with swift test.

MIT

Mattt (@mattt)