Add rule MD056/table-column-count (fixes #92).

lib/md056.js

@@ -0,0 +1,44 @@
+// @ts-check
+
+"use strict";
+
+const { addErrorDetailIf } = require("../helpers");
+const { filterByTypes } = require("../helpers/micromark.cjs");
+
+const makeRange = (start, end) => [ start, end - start + 1 ];
+
+module.exports = {
+  "names": [ "MD056", "table-column-count" ],
+  "description": "Table column count",
+  "tags": [ "table" ],
+  "function": function MD056(params, onError) {
+    const tables = filterByTypes(params.parsers.micromark.tokens, [ "table" ]);
+    for (const table of tables) {
+      const rows = filterByTypes(table.children, [ "tableDelimiterRow", "tableRow" ]);
+      let expectedCount = 0;
+      for (const row of rows) {
+        const cells = filterByTypes(row.children, [ "tableData", "tableDelimiter", "tableHeader" ]);
+        const actualCount = cells.length;
+        expectedCount ||= actualCount;
+        let detail = null;
+        let range = null;
+        if (actualCount < expectedCount) {
+          detail = "Too few cells, row will be missing data";
+          range = [ row.endColumn - 1, 1 ];
+        } else if (expectedCount < actualCount) {
+          detail = "Too many cells, extra data will be missing";
+          range = makeRange(cells[expectedCount].startColumn, row.endColumn - 1);
+        }
+        addErrorDetailIf(
+          onError,
+          row.endLine,
+          expectedCount,
+          actualCount,
+          detail,
+          null,
+          range
+        );
+      }
+    }
+  }
+}