From a55616030664891c20ffae449728fc58aa757916 Mon Sep 17 00:00:00 2001
From: Alexander Wang <alex@terrastruct.com>
Date: Tue, 7 Mar 2023 09:00:45 -0800
Subject: [PATCH] validate markdown

---
 ci/release/changelogs/next.md                 |  1 +
 d2compiler/compile.go                         | 24 +++++++++++++++++--
 d2compiler/compile_test.go                    | 20 ++++++++++++++++
 .../TestCompile/unsemantic_markdown.exp.json  | 12 ++++++++++
 .../unsemantic_markdown_2.exp.json            | 12 ++++++++++
 5 files changed, 67 insertions(+), 2 deletions(-)
 create mode 100644 testdata/d2compiler/TestCompile/unsemantic_markdown.exp.json
 create mode 100644 testdata/d2compiler/TestCompile/unsemantic_markdown_2.exp.json

diff --git a/ci/release/changelogs/next.md b/ci/release/changelogs/next.md
index d3ac356a3..256afb7d9 100644
--- a/ci/release/changelogs/next.md
+++ b/ci/release/changelogs/next.md
@@ -4,6 +4,7 @@
 
 - ELK nodes with > 1 connection grow to ensure padding around ports [#981](https://github.com/terrastruct/d2/pull/981)
 - Using a style keyword incorrectly in connections returns clear error message [#989](https://github.com/terrastruct/d2/pull/989)
+- Unsemantic Markdown returns clear error message [#994](https://github.com/terrastruct/d2/pull/994)
 
 #### Bugfixes ⛑️
 
diff --git a/d2compiler/compile.go b/d2compiler/compile.go
index 6fa9106f3..729f2e46f 100644
--- a/d2compiler/compile.go
+++ b/d2compiler/compile.go
@@ -1,6 +1,7 @@
 package d2compiler
 
 import (
+	"encoding/xml"
 	"fmt"
 	"io"
 	"net/url"
@@ -15,6 +16,7 @@ import (
 	"oss.terrastruct.com/d2/d2ir"
 	"oss.terrastruct.com/d2/d2parser"
 	"oss.terrastruct.com/d2/d2target"
+	"oss.terrastruct.com/d2/lib/textmeasure"
 )
 
 type CompileOptions struct {
@@ -224,9 +226,27 @@ func (c *compiler) compileLabel(attrs *d2graph.Attributes, f d2ir.Node) {
 		if ok {
 			attrs.Language = fullTag
 		}
-		if attrs.Language == "markdown" || attrs.Language == "latex" {
+		switch attrs.Language {
+		case "latex":
 			attrs.Shape.Value = d2target.ShapeText
-		} else {
+		case "markdown":
+			rendered, err := textmeasure.RenderMarkdown(scalar.ScalarString())
+			if err != nil {
+				c.errorf(f.LastPrimaryKey(), "malformed Markdown")
+			}
+			rendered = "<div>" + rendered + "</div>"
+			var xmlParsed interface{}
+			err = xml.Unmarshal([]byte(rendered), &xmlParsed)
+			if err != nil {
+				switch xmlErr := err.(type) {
+				case *xml.SyntaxError:
+					c.errorf(f.LastPrimaryKey(), "malformed Markdown: %s", xmlErr.Msg)
+				default:
+					c.errorf(f.LastPrimaryKey(), "malformed Markdown: %s", err.Error())
+				}
+			}
+			attrs.Shape.Value = d2target.ShapeText
+		default:
 			attrs.Shape.Value = d2target.ShapeCode
 		}
 		attrs.Label.Value = scalar.ScalarString()
diff --git a/d2compiler/compile_test.go b/d2compiler/compile_test.go
index 0444f00ae..e40083b34 100644
--- a/d2compiler/compile_test.go
+++ b/d2compiler/compile_test.go
@@ -869,6 +869,26 @@ b.(x -> y)[0]: two
 				}
 			},
 		},
+		{
+			name: "unsemantic_markdown",
+
+			text: `test:|
+foobar
+<p>
+|
+`,
+			expErr: `d2/testdata/d2compiler/TestCompile/unsemantic_markdown.d2:1:1: malformed Markdown: element <p> closed by </div>`,
+		},
+		{
+			name: "unsemantic_markdown_2",
+
+			text: `test:|
+foo<br>
+bar
+|
+`,
+			expErr: `d2/testdata/d2compiler/TestCompile/unsemantic_markdown_2.d2:1:1: malformed Markdown: element <br> closed by </p>`,
+		},
 		{
 			name: "edge_map",
 
diff --git a/testdata/d2compiler/TestCompile/unsemantic_markdown.exp.json b/testdata/d2compiler/TestCompile/unsemantic_markdown.exp.json
new file mode 100644
index 000000000..b0dbf4465
--- /dev/null
+++ b/testdata/d2compiler/TestCompile/unsemantic_markdown.exp.json
@@ -0,0 +1,12 @@
+{
+  "graph": null,
+  "err": {
+    "ioerr": null,
+    "errs": [
+      {
+        "range": "d2/testdata/d2compiler/TestCompile/unsemantic_markdown.d2,0:0:0-3:1:19",
+        "errmsg": "d2/testdata/d2compiler/TestCompile/unsemantic_markdown.d2:1:1: malformed Markdown: element <p> closed by </div>"
+      }
+    ]
+  }
+}
diff --git a/testdata/d2compiler/TestCompile/unsemantic_markdown_2.exp.json b/testdata/d2compiler/TestCompile/unsemantic_markdown_2.exp.json
new file mode 100644
index 000000000..adfb7f026
--- /dev/null
+++ b/testdata/d2compiler/TestCompile/unsemantic_markdown_2.exp.json
@@ -0,0 +1,12 @@
+{
+  "graph": null,
+  "err": {
+    "ioerr": null,
+    "errs": [
+      {
+        "range": "d2/testdata/d2compiler/TestCompile/unsemantic_markdown_2.d2,0:0:0-3:1:20",
+        "errmsg": "d2/testdata/d2compiler/TestCompile/unsemantic_markdown_2.d2:1:1: malformed Markdown: element <br> closed by </p>"
+      }
+    ]
+  }
+}