Custom linter to check code quality (#2753)

ts/util/lint/analyze_exceptions.ts

@@ -0,0 +1,29 @@
+// tslint:disable no-console
+
+import { join } from 'path';
+
+import { fromPairs, groupBy, map } from 'lodash';
+
+import { ExceptionType } from './types';
+import { loadJSON } from './util';
+
+const exceptionsPath = join(__dirname, 'exceptions.json');
+const exceptions: Array<ExceptionType> = loadJSON(exceptionsPath);
+const byRule = groupBy(exceptions, 'rule');
+
+const byRuleThenByCategory = fromPairs(
+  map(byRule, (list, ruleName) => {
+    const byCategory = groupBy(list, 'reasonCategory');
+
+    return [
+      ruleName,
+      fromPairs(
+        map(byCategory, (innerList, categoryName) => {
+          return [categoryName, innerList.length];
+        })
+      ),
+    ];
+  })
+);
+
+console.log(JSON.stringify(byRuleThenByCategory, null, '  '));