fix: Add a plugin to fix the last column in a table (#7036)

shared/editor/plugins/FixTables.ts

@@ -0,0 +1,58 @@
+import { Node } from "prosemirror-model";
+import { EditorState, Plugin, Transaction } from "prosemirror-state";
+import { TableMap } from "prosemirror-tables";
+import { changedDescendants } from "../lib/changedDescendants";
+import { getCellsInColumn } from "../queries/table";
+
+/**
+ * A ProseMirror plugin that fixes the last column in a table to ensure it fills the remaining width.
+ */
+export class FixTablesPlugin extends Plugin {
+  constructor() {
+    super({
+      appendTransaction: (_transactions, oldState, state) => {
+        let tr: Transaction | undefined;
+        const check = (node: Node) => {
+          if (node.type.spec.tableRole === "table") {
+            tr = this.fixTable(state, node, tr);
+          }
+        };
+        if (!oldState) {
+          state.doc.descendants(check);
+        } else if (oldState.doc !== state.doc) {
+          changedDescendants(oldState.doc, state.doc, 0, check);
+        }
+        return tr;
+      },
+    });
+  }
+
+  private fixTable(
+    state: EditorState,
+    table: Node,
+    tr: Transaction | undefined
+  ): Transaction | undefined {
+    let fixed = false;
+    const map = TableMap.get(table);
+    if (!tr) {
+      tr = state.tr;
+    }
+
+    // If the table has only one column, remove the colwidth attribute on all cells
+    if (map.width === 1) {
+      const cells = getCellsInColumn(0)(state);
+      cells.forEach((pos) => {
+        const node = state.doc.nodeAt(pos);
+        if (node?.attrs.colspan) {
+          fixed = true;
+          tr = tr!.setNodeMarkup(pos, undefined, {
+            ...node?.attrs,
+            colwidth: null,
+          });
+        }
+      });
+    }
+
+    return fixed ? tr : undefined;
+  }
+}