fix: don't render terminal linebreaks

Our markdown syntax does not support teminal line-breaks, either
in blocks like a paragraph or just in text.

We had correctly been suppressing rendering the slash-escaped line
break when it appeared in a paragraph, but not in text

packages/@atjson/renderer-commonmark/src/index.ts

@@ -465,12 +465,7 @@ export default class CommonmarkRenderer extends Renderer {
   *LineBreak(_: any, context: Context): Generator<void, string, string[]> {
     // Line breaks cannot end markdown block elements or paragraphs
     // https://spec.commonmark.org/0.29/#example-641
-    if (
-      context.parent &&
-      "parents" in context.parent &&
-      context.parent.parents &&
-      context.next == null
-    ) {
+    if (!context.next) {
       return "";
     }
 

packages/@atjson/renderer-commonmark/test/line-break.test.ts

@@ -0,0 +1,105 @@
+import CommonmarkRenderer from "../src";
+
+describe("terminal line breaks are removed", () => {
+  test("in text", () => {
+    const document = {
+      text: "\ufffctest\ufffc",
+      blocks: [
+        {
+          id: "B00000000",
+          type: "text",
+          parents: [],
+          selfClosing: false,
+          attributes: {},
+        },
+        {
+          id: "B00000000",
+          type: "line-break",
+          parents: ["text"],
+          selfClosing: true,
+          attributes: {},
+        },
+      ],
+      marks: [],
+    };
+
+    expect(CommonmarkRenderer.render(document)).toBe("test");
+  });
+
+  test("in paragraph", () => {
+    const document = {
+      text: "\ufffctest\ufffc",
+      blocks: [
+        {
+          id: "B00000000",
+          type: "paragraph",
+          parents: [],
+          selfClosing: false,
+          attributes: {},
+        },
+        {
+          id: "B00000000",
+          type: "line-break",
+          parents: ["paragraph"],
+          selfClosing: true,
+          attributes: {},
+        },
+      ],
+      marks: [],
+    };
+
+    expect(CommonmarkRenderer.render(document)).toBe("test\n\n");
+  });
+});
+
+describe("are slash escaped", () => {
+  test("in text", () => {
+    const document = {
+      text: "\ufffcline 1\ufffcline 2",
+      blocks: [
+        {
+          id: "B00000000",
+          type: "text",
+          parents: [],
+          selfClosing: false,
+          attributes: {},
+        },
+        {
+          id: "B00000000",
+          type: "line-break",
+          parents: ["text"],
+          selfClosing: true,
+          attributes: {},
+        },
+      ],
+      marks: [],
+    };
+
+    expect(CommonmarkRenderer.render(document)).toBe("line 1\\\nline 2");
+  });
+
+  test("in paragraph", () => {
+    const document = {
+      text: "\ufffcline 1\ufffcline 2",
+      blocks: [
+        {
+          id: "B00000000",
+          type: "paragraph",
+          parents: [],
+          selfClosing: false,
+          attributes: {},
+        },
+        {
+          id: "B00000000",
+          type: "line-break",
+          parents: ["paragraph"],
+          selfClosing: true,
+          attributes: {},
+        },
+      ],
+      marks: [],
+    };
+
+    expect(CommonmarkRenderer.render(document)).toBe("line 1\\\nline 2\n\n");
+  });
+});