refactor(dev-infra): Add support for groups in the conditions evaluator (#38164)

Conditions can refer to the groups array that is a list of the preceding groups.
This commit adds support to the verification for those conditions.

This commit also adds some tests to the parsing and condition matching
to ensure everything works as expected.

PR Close #38164

dev-infra/pullapprove/group.ts

@@ -6,14 +6,15 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {error} from '../utils/console';
+import {error, warn} from '../utils/console';
 import {convertConditionToFunction} from './condition_evaluator';
 import {PullApproveGroupConfig} from './parse-yaml';
+import {PullApproveGroupStateDependencyError} from './pullapprove_arrays';
 
 /** A condition for a group. */
 interface GroupCondition {
   expression: string;
-  checkFn: (files: string[]) => boolean;
+  checkFn: (files: string[], groups: PullApproveGroup[]) => boolean;
   matchedFiles: Set<string>;
 }
 
@@ -39,7 +40,9 @@ export class PullApproveGroup {
   /** List of conditions for the group. */
   conditions: GroupCondition[] = [];
 
-  constructor(public groupName: string, config: PullApproveGroupConfig) {
+  constructor(
+      public groupName: string, config: PullApproveGroupConfig,
+      readonly precedingGroups: PullApproveGroup[] = []) {
     this._captureConditions(config);
   }
 
@@ -78,18 +81,30 @@ export class PullApproveGroup {
   testFile(filePath: string): boolean {
     return this.conditions.every(({matchedFiles, checkFn, expression}) => {
       try {
-        const matchesFile = checkFn([filePath]);
+        const matchesFile = checkFn([filePath], this.precedingGroups);
         if (matchesFile) {
           matchedFiles.add(filePath);
         }
         return matchesFile;
       } catch (e) {
-        const errMessage = `Condition could not be evaluated: \n\n` +
-            `From the [${this.groupName}] group:\n` +
-            ` - ${expression}` +
-            `\n\n${e.message} ${e.stack}\n\n`;
-        error(errMessage);
-        process.exit(1);
+        // In the case of a condition that depends on the state of groups we want to just
+        // warn that the verification can't accurately evaluate the condition and then
+        // continue processing. Other types of errors fail the verification, as conditions
+        // should otherwise be able to execute without throwing.
+        if (e instanceof PullApproveGroupStateDependencyError) {
+          const errMessage = `Condition could not be evaluated: \n` +
+              `${e.message}\n` +
+              `From the [${this.groupName}] group:\n` +
+              ` - ${expression}`;
+          warn(errMessage);
+        } else {
+          const errMessage = `Condition could not be evaluated: \n\n` +
+              `From the [${this.groupName}] group:\n` +
+              ` - ${expression}` +
+              `\n\n${e.message} ${e.stack}\n\n`;
+          error(errMessage);
+          process.exit(1);
+        }
       }
     });
   }