fix: reject non-string rules:if

A rules entry with an empty if key parses as null and hit string methods
directly, so a config mistake surfaced as a TypeError.

Author: firecow

src/utils.ts

@@ -228,6 +228,7 @@ export class Utils {
 
     static evaluateRuleIf (ruleIf: string | undefined, envs: {[key: string]: string}): boolean {
         if (ruleIf === undefined) return true;
+        assert(typeof ruleIf === "string", chalk`This GitLab CI configuration is invalid: {blueBright rules:if} must be a string, but got {red ${JSON.stringify(ruleIf)}}`);
         assert(!/\$\{\w+\}/.test(ruleIf), chalk`rules:rule if invalid expression syntax: {blueBright ${ruleIf}}\nuse {green $VAR} not {red \${VAR\}} in rules:if`);
         let evalStr = ruleIf;
 

tests/rules.test.ts

@@ -334,3 +334,11 @@ test.concurrent("https://github.com/firecow/gitlab-ci-local/issues/1252", () =>
     const rulesResult = Utils.getRulesResult({argv, cwd: "", rules, variables}, gitData);
     expect(rulesResult).toEqual({when: "on_success", allowFailure: false, variables: undefined});
 });
+
+test.concurrent("https://github.com/firecow/gitlab-ci-local/issues/1841", () => {
+    for (const ruleIf of [null, 1, true, ["a"]]) {
+        const rules = [ {if: ruleIf} as any ];
+        expect(() => Utils.getRulesResult({argv, cwd: "", rules, variables: {}}, gitData))
+            .toThrow(/must be a string, but got/);
+    }
+});