Throw error when empty regex in custom param types

Fixes #754

src/validateConfig.ts

@@ -1,5 +1,6 @@
 import { FormatOptions } from './FormatOptions.js';
 import { ParamItems } from './formatter/Params.js';
+import { ParamTypes } from './lexer/TokenizerOptions.js';
 
 export class ConfigError extends Error {}
 
@@ -29,10 +30,23 @@ export function validateConfig(cfg: FormatOptions): FormatOptions {
     console.warn('WARNING: All "params" option values should be strings.');
   }
 
+  if (cfg.paramTypes && !validateParamTypes(cfg.paramTypes)) {
+    throw new ConfigError(
+      'Empty regex given in custom paramTypes. That would result in matching infinite amount of parameters.'
+    );
+  }
+
   return cfg;
 }
 
 function validateParams(params: ParamItems | string[]): boolean {
   const paramValues = params instanceof Array ? params : Object.values(params);
   return paramValues.every(p => typeof p === 'string');
 }
+
+function validateParamTypes(paramTypes: ParamTypes): boolean {
+  if (paramTypes.custom && Array.isArray(paramTypes.custom)) {
+    return paramTypes.custom.every(p => p.regex !== '');
+  }
+  return true;
+}

test/options/paramTypes.ts

@@ -110,5 +110,15 @@ export default function supportsParamTypes(format: FormatFn) {
           {schema}.{table}
       `);
     });
+
+    it('does not enter infinite loop when empty regex given', () => {
+      expect(() =>
+        format('SELECT foo FROM bar', {
+          paramTypes: { custom: [{ regex: '' }] },
+        })
+      ).toThrow(
+        'Empty regex given in custom paramTypes. That would result in matching infinite amount of parameters.'
+      );
+    });
   });
 }