Add D2 output format

README.md

@@ -12,8 +12,14 @@ Supported formats:
 * [DBML](https://www.dbml.org/)
 * [QuickDBD](https://www.quickdatabasediagrams.com)
 * [Mermaid](https://mermaid-js.github.io/mermaid/#/entityRelationshipDiagram)
+* [D2](https://d2lang.com)
 
 ![Simple blog demo](assets/simple_blog_dot_demo.png)
+
+The **D2** format renders the rich tier — clusters, `Ecto.Enum` values, embedded schemas, and primary/foreign keys:
+
+![Simple blog demo (D2)](assets/simple_blog_d2_demo.svg)
+
 <details>
   <summary>Definition of schemas</summary>
 

examples_generator.exs

@@ -2,10 +2,10 @@ defmodule Ecto.ERD.ExamplesGenerator do
   require Logger
 
   @shared_examples [
-    [name: "Default", formats: [:dbml, :dot, :qdbd, :puml, :mmd]],
+    [name: "Default", formats: [:dbml, :dot, :qdbd, :puml, :mmd, :d2]],
     [
       name: "No fields",
-      formats: [:dot, :mmd],
+      formats: [:dot, :mmd, :d2],
       config: """
       [
         columns: []
@@ -14,7 +14,7 @@ defmodule Ecto.ERD.ExamplesGenerator do
     ],
     [
       name: "Contexts as clusters",
-      formats: [:dbml, :dot, :puml],
+      formats: [:dbml, :dot, :puml, :d2],
       config: """
       alias Ecto.ERD.Node
 
@@ -32,7 +32,7 @@ defmodule Ecto.ERD.ExamplesGenerator do
     ],
     [
       name: "Contexts as clusters (no fields)",
-      formats: [:dot, :puml],
+      formats: [:dot, :puml, :d2],
       config: """
       alias Ecto.ERD.Node
 
@@ -150,7 +150,7 @@ defmodule Ecto.ERD.ExamplesGenerator do
             ],
             [
               name: "Only embedded schemas",
-              formats: [:dot, :puml],
+              formats: [:dot, :puml, :d2],
               config: """
               alias Ecto.ERD.Node
 
@@ -167,11 +167,12 @@ defmodule Ecto.ERD.ExamplesGenerator do
   }
 
   @formats %{
-    dot: %{examples_dir: "examples/dot", name: "DOT", image?: true},
-    dbml: %{examples_dir: "examples/dbml", name: "DBML", image?: false},
-    qdbd: %{examples_dir: "examples/quick_dbd", name: "QuickDBD", image?: false},
-    puml: %{examples_dir: "examples/plantuml", name: "PlantUML", image?: true},
-    mmd: %{examples_dir: "examples/mermaid", name: "Mermaid", image?: false}
+    dot: %{examples_dir: "examples/dot", name: "DOT", image_ext: "png"},
+    dbml: %{examples_dir: "examples/dbml", name: "DBML"},
+    qdbd: %{examples_dir: "examples/quick_dbd", name: "QuickDBD"},
+    puml: %{examples_dir: "examples/plantuml", name: "PlantUML", image_ext: "png"},
+    mmd: %{examples_dir: "examples/mermaid", name: "Mermaid"},
+    d2: %{examples_dir: "examples/d2", name: "D2", image_ext: "svg"}
   }
 
   def run(source_url_root) do
@@ -235,8 +236,8 @@ defmodule Ecto.ERD.ExamplesGenerator do
                 ])
 
               image_url =
-                if @formats[format].image? do
-                  Path.rootname(document_url) <> ".png"
+                if image_ext = @formats[format][:image_ext] do
+                  Path.rootname(document_url) <> "." <> image_ext
                 end
 
               [
@@ -313,10 +314,11 @@ defmodule Ecto.ERD.ExamplesGenerator do
       end
 
       {:ok, new_output_content} = File.read(output_path)
+      image_ext = @formats[format][:image_ext]
 
-      if @formats[format].image? and
+      if image_ext &&
            (old_output_content != new_output_content or
-              not File.exists?(Path.rootname(output_path) <> ".png")) do
+              not File.exists?(Path.rootname(output_path) <> "." <> image_ext)) do
         Logger.debug("Generating image from #{output_path}")
         generate_image(format, output_path)
       end
@@ -333,6 +335,10 @@ defmodule Ecto.ERD.ExamplesGenerator do
     System.cmd("plantuml", [file], env: %{"PLANTUML_LIMIT_SIZE" => "8192"})
   end
 
+  defp generate_image(:d2, file) do
+    System.cmd("d2", [file, Path.rootname(file) <> ".svg"])
+  end
+
   defp init_project(project_name, repo, commit) do
     Logger.debug("#{project_name}: clone repo")
     System.cmd("git", ["clone", repo, project_name], cd: "tmp/repos")

lib/ecto/erd/document.ex

@@ -7,6 +7,7 @@ defmodule Ecto.ERD.Document do
       when is_function(map_node_callback, 1) do
     document_module =
       case format do
+        ".d2" -> Ecto.ERD.Document.D2
         ".dbml" -> Ecto.ERD.Document.DBML
         ".dot" -> Ecto.ERD.Document.Dot
         ".mmd" -> Ecto.ERD.Document.Mermaid