feat(gh75): extract target branched from pr labels (#112)

src/service/args/args-parser.ts

@@ -16,14 +16,18 @@ export default abstract class ArgsParser {
   public parse(): Args {
     const args = this.readArgs();
 
+    if (!args.pullRequest) {
+      throw new Error("Missing option: pull request must be provided");
+    }
     // validate and fill with defaults
-    if (!args.pullRequest || !args.targetBranch || args.targetBranch.trim().length == 0) {
-      throw new Error("Missing option: pull request and target branches must be provided");
+    if ((!args.targetBranch || args.targetBranch.trim().length == 0) && !args.targetBranchPattern) {
+      throw new Error("Missing option: target branch(es) or target regular expression must be provided");
     }
     
     return {
       pullRequest: args.pullRequest,
       targetBranch: args.targetBranch,
+      targetBranchPattern: args.targetBranchPattern,
       dryRun: this.getOrDefault(args.dryRun, false),
       auth: this.getOrDefault(args.auth),
       folder: this.getOrDefault(args.folder),

src/service/args/args.types.ts

@@ -3,7 +3,8 @@
  */
 export interface Args {
   // NOTE: keep targetBranch as singular and of type string for backward compatibilities
-  targetBranch: string,  // comma separated list of branches on the target repo where the change should be backported to
+  targetBranch?: string,  // comma separated list of branches on the target repo where the change should be backported to
+  targetBranchPattern?: string, // regular expression to extract target branch(es) from pull request labels
   pullRequest: string, // url of the pull request to backport
   dryRun?: boolean, // if enabled do not push anything remotely
   auth?: string, // git service auth, like github token

src/service/args/cli/cli-args-parser.ts

@@ -11,6 +11,7 @@ export default class CLIArgsParser extends ArgsParser {
       .version(version)
       .description(description)
       .option("-tb, --target-branch <branches>", "comma separated list of branches where changes must be backported to")
+      .option("-tbp, --target-branch-pattern <pattern>", "regular expression pattern to extract target branch(es) from pr labels, the branches will be extracted from the pattern's required `target` named capturing group")
       .option("-pr, --pull-request <pr-url>", "pull request url, e.g., https://github.com/kiegroup/git-backporting/pull/1")
       .option("-d, --dry-run", "if enabled the tool does not create any pull request nor push anything remotely")
       .option("-a, --auth <auth>", "git authentication string, if not provided fallback by looking for existing env variables like GITHUB_TOKEN")
@@ -49,6 +50,7 @@ export default class CLIArgsParser extends ArgsParser {
         auth: opts.auth,
         pullRequest: opts.pullRequest,
         targetBranch: opts.targetBranch,
+        targetBranchPattern: opts.targetBranchPattern,
         folder: opts.folder,
         gitClient: opts.gitClient,
         gitUser: opts.gitUser,

src/service/args/gha/gha-args-parser.ts

@@ -16,7 +16,8 @@ export default class GHAArgsParser extends ArgsParser {
         dryRun: getAsBooleanOrDefault(getInput("dry-run")),
         auth: getOrUndefined(getInput("auth")),
         pullRequest: getInput("pull-request"),
-        targetBranch: getInput("target-branch"),
+        targetBranch: getOrUndefined(getInput("target-branch")),
+        targetBranchPattern: getOrUndefined(getInput("target-reg-exp")),
         folder: getOrUndefined(getInput("folder")),
         gitClient: getOrUndefined(getInput("git-client")),
         gitUser: getOrUndefined(getInput("git-user")),

src/service/configs/pullrequest/pr-configs-parser.ts

@@ -26,7 +26,17 @@ export default class PullRequestConfigsParser extends ConfigsParser {
 
     const folder: string = args.folder ?? this.getDefaultFolder();
 
-    const targetBranches: string[] = [...new Set(getAsCommaSeparatedList(args.targetBranch)!)];
+    let targetBranches: string[] = [];
+    if (args.targetBranchPattern) {
+      // parse labels to extract target branch(es)
+      targetBranches = this.getTargetBranchesFromLabels(args.targetBranchPattern, pr.labels);
+      if (targetBranches.length === 0) {
+        throw new Error(`Unable to extract target branches with regular expression "${args.targetBranchPattern}"`);
+      }
+    } else {
+      // target branch must be provided if targetRegExp is missing
+      targetBranches = [...new Set(getAsCommaSeparatedList(args.targetBranch!)!)];
+    }
     const bpBranchNames: string[] = [...new Set(args.bpBranchName ? (getAsCleanedCommaSeparatedList(args.bpBranchName) ?? []) : [])];
 
     if (bpBranchNames.length > 1 && bpBranchNames.length != targetBranches.length) {
@@ -52,6 +62,33 @@ export default class PullRequestConfigsParser extends ConfigsParser {
     return "bp";
   }
 
+  /**
+   * Parse the provided labels and return a list of target branches
+   * obtained by applying the provided pattern as regular expression extractor
+   * @param pattern reg exp pattern to extract target branch from label name
+   * @param labels list of labels to check
+   * @returns list of target branches
+   */
+  private getTargetBranchesFromLabels(pattern: string, labels: string[]): string[] {
+    this.logger.debug(`Extracting branches from [${labels}] using ${pattern}`);
+    const regExp = new RegExp(pattern);
+
+    const branches: string[] = [];
+    for (const l of labels) {
+      const result = regExp.exec(l);
+
+      if (result?.groups) {
+        const { target } = result.groups;
+        if (target){
+          branches.push(target);
+        }
+      }
+    }
+
+
+    return [...new Set(branches)];
+  }
+
   /**
    * Create a backport pull request starting from the target branch and 
    * the original pr to be backported