Ensure labels exist before creating PRs

`gh` does not create labels automatically when you create a PR
referencing one. If the label does not exist, the PR creation fails.

This commit adds an `ensure_labels` step before creating the PRs that
lists and creates the labels that will be used in the following steps.

Author: neilvcarvalho

lib/executor.rb

@@ -111,6 +111,7 @@ def handle_open(action)
           )
         end
 
+        @gh.ensure_labels(@labels)
         @git.checkout_fresh_branch(branch: spec.branch, base: @base)
         committed = pin_packages_and_commit(spec)
         if !committed

lib/gh_client.rb

@@ -65,6 +65,23 @@ def create_pr(branch:, base:, title:, body:, labels: [])
         result.stdout.strip[%r{/pull/(\d+)}, 1]&.to_i
       end
 
+      # Ensures every label in +labels+ exists in the repo, creating any that
+      # are missing. Called once before opening PRs so that `create_pr` never
+      # fails with "label does not exist". Missing labels are created with a
+      # neutral default color; existing labels are left untouched.
+      def ensure_labels(labels)
+        return if labels.empty?
+        existing = list_label_names
+        labels.each do |label|
+          next if existing.include?(label)
+          @runner.run(
+            "gh", "label", "create", label,
+            "--repo", @repo,
+            "--color", "0075ca"
+          )
+        end
+      end
+
       # Edits an existing PR's title and body. Used after force-pushing a
       # changed branch — the body must be re-rendered so the metadata
       # block reflects the new package set.
@@ -98,6 +115,19 @@ def close_pr(number:, comment: nil)
 
       private
 
+      def list_label_names
+        result = @runner.run(
+          "gh", "label", "list",
+          "--repo", @repo,
+          "--json", "name",
+          "--limit", "200"
+        )
+        return [] unless result.success?
+        JSON.parse(result.stdout.force_encoding("UTF-8")).map { |l| l["name"] }
+      rescue JSON::ParserError
+        []
+      end
+
       def parse_pr_list(stdout, branch_prefix)
         parsed = JSON.parse(stdout.force_encoding("UTF-8"))
         # `head:foo/` is a *search* term, not a strict filter — GitHub's

test/executor_test.rb

@@ -26,6 +26,9 @@ def initialize
       @next_pr_number = 1000
     end
 
+    def ensure_labels(labels)
+    end
+
     def create_pr(branch:, base:, title:, body:, labels: [])
       @created << {branch: branch, base: base, title: title, body: body, labels: labels}
       n = @next_pr_number

test/gh_client_test.rb

@@ -115,6 +115,49 @@ def test_list_open_prs_propagates_gh_failure
     assert_includes err.message, "auth required"
   end
 
+  # ---- ensure_labels ----
+
+  def test_ensure_labels_is_a_no_op_when_labels_is_empty
+    @client.ensure_labels([])
+    assert_equal 0, @runner.calls.size
+  end
+
+  def test_ensure_labels_creates_missing_labels
+    @runner.add(
+      pattern: ["gh", "label", "list", "--repo", REPO, "--json", "name", "--limit", "200"],
+      stdout: +%([{"name":"dependencies"}])
+    )
+    @runner.add(
+      pattern: ["gh", "label", "create", "javascript", "--repo", REPO, "--color", "0075ca"],
+      stdout: +""
+    )
+    @client.ensure_labels(%w[dependencies javascript])
+    assert_equal 2, @runner.calls.size
+  end
+
+  def test_ensure_labels_skips_labels_that_already_exist
+    @runner.add(
+      pattern: ["gh", "label", "list", "--repo", REPO, "--json", "name", "--limit", "200"],
+      stdout: +%([{"name":"dependencies"},{"name":"javascript"}])
+    )
+    @client.ensure_labels(%w[dependencies javascript])
+    assert_equal 1, @runner.calls.size
+  end
+
+  def test_ensure_labels_tolerates_gh_label_list_failure
+    @runner.add(
+      pattern: ["gh", "label", "list", "--repo", REPO, "--json", "name", "--limit", "200"],
+      stderr: "not found",
+      exit_code: 1
+    )
+    @runner.add(
+      pattern: ["gh", "label", "create", "dependencies", "--repo", REPO, "--color", "0075ca"],
+      stdout: +""
+    )
+    @client.ensure_labels(%w[dependencies])
+    assert_equal 2, @runner.calls.size
+  end
+
   # ---- create_pr ----
 
   def test_create_pr_invokes_gh_with_title_body_branch_and_base