Add D2 support

.github/workflows/ci.yaml

@@ -173,6 +173,27 @@ jobs:
       - name: Render
         run: make PANDOC=/opt/quarto/bin/tools/x86_64/pandoc test-cetz
 
+  D2:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: true
+    container:
+      image: ghcr.io/quarto-dev/quarto:latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install dependencies
+        run: |
+          apt-get -q --no-allow-insecure-repositories update && \
+          apt-get install --no-install-recommends --assume-yes \
+            ca-certificates curl make && \
+          curl -fsSL https://d2lang.com/install.sh | sh -s --
+
+      - name: Render
+        run: make PANDOC=/opt/quarto/bin/tools/x86_64/pandoc test-d2
+
   Quarto:
     runs-on: ubuntu-latest
     strategy:

README.md

@@ -4,7 +4,7 @@ Diagram Generator
 This Lua filter is used to create figures from code blocks: images
 are generated from the code with the help of external programs.
 The filter processes diagram code for Asymptote, Graphviz,
-Mermaid, PlantUML, and Ti*k*Z.
+Mermaid, PlantUML, Ti*k*Z, and D2.
 
 
 Usage
@@ -103,6 +103,7 @@ that can be used to specify a specific executable.
 | [PlantUML]  | `plantuml`        | `plantuml` | `PLANTUML_BIN`  |
 | [Ti*k*Z]    | `tikz`            | `pdflatex` | `PDFLATEX_BIN`  |
 | [cetz]      | `cetz`            | `typst`    | `TYPST_BIN`     |
+| [D2]        | `d2`              | `d2`       | `D2_BIN`        |
 
 ### Other diagram engines
 
@@ -115,6 +116,7 @@ The filter can be extended with local packages; see
 [PlantUML]: https://plantuml.com/
 [Ti*k*Z]: https://github.com/pgf-tikz/pgf
 [Cetz]: https://github.com/cetz-package/cetz
+[D2]: https://d2lang.com/
 
 Figure options
 --------------

_extensions/diagram/diagram.lua

@@ -291,13 +291,43 @@ local cetz = {
   end,
 }
 
+--- D2 engine for the D2 language
+local d2 = {
+  line_comment_start = '#',
+  mime_types = mime_types_set{'png', 'svg'},
+
+  compile = function (self, code, user_opts)
+    return with_temporary_directory('diagram', function (tmpdir)
+      return with_working_directory(tmpdir, function ()
+        -- D2 format identifiers correspond to common file extensions.
+        local mime_type = self.mime_type or 'image/svg+xml'
+        local file_extension = extension_for_mimetype[mime_type]
+        local infile = 'diagram.d2'
+        local outfile = 'diagram.' .. file_extension
+
+        args = {'--bundle', '--pad=0', '--scale=1'}
+
+        table.insert(args, infile)
+        table.insert(args, outfile)
+
+        write_file(infile, code)
+
+        pipe(self.execpath or 'd2', args, '')
+
+        return read_file(outfile), mime_type
+      end)
+    end)
+  end,
+}
+
 local default_engines = {
   asymptote = asymptote,
   dot       = graphviz,
   mermaid   = mermaid,
   plantuml  = plantuml,
   tikz      = tikz,
   cetz      = cetz,
+  d2        = d2,
 }
 
 --

test/expected-d2.html

@@ -0,0 +1,6 @@
+<h3 id="d2">D2</h3>
+<p>D2 is a Go-based diagramming and charting tool.</p>
+<figure>
+<img src="hello-world.svg" alt="Hello, World!" />
+<figcaption aria-hidden="true"><p>Hello, World!</p></figcaption>
+</figure>

test/input-d2.md

@@ -0,0 +1,7 @@
+### D2
+
+D2 is a Go-based diagramming and charting tool.
+
+```{.d2 caption="Hello, World!" filename="hello-world.svg"}
+x -> y: hello world
+```

test/test-d2.yaml

@@ -0,0 +1,10 @@
+input-files: ['test/input-d2.md']
+filters:
+  - diagram.lua
+to: html
+metadata:
+  pagetitle: D2 diagram
+  diagram:
+    cache: false
+variables:
+  document-css: false