Announce public API changes from main only

fastlane/Fastfile

@@ -2501,17 +2501,19 @@ platform :ios do
     end
 
 
-    # Regenerated baselines make the freshness diff empty, so the gate needs the merge base.
+    # Regenerated baselines make the freshness diff empty, so the gate needs an earlier base.
     runner = ->(*command) { sh(*command, log: false) }
-    merge_base = ApiDiffHelper.resolve_merge_base(runner: runner)
-    UI.message("Comparing against the merge base #{merge_base}")
+    branch = ApiDiffHelper.current_branch(runner: runner)
+    on_main = ApiDiffHelper.main_branch?(branch)
+    comparison_base = ApiDiffHelper.resolve_comparison_base(runner: runner, branch: branch)
+    UI.message("Comparing #{branch} against #{comparison_base}")
 
     breaks_by_scheme = {}
     reports_by_target = {}
 
     schemes.each do |scheme|
-      base_dir = File.join(ApiDiffHelper::MERGE_BASE_SWIFTINTERFACE_DIR, scheme)
-      ApiDiffHelper.extract_baselines_at(merge_base, base_dir, scheme, runner: runner)
+      base_dir = File.join(ApiDiffHelper::BASE_SWIFTINTERFACE_DIR, scheme)
+      ApiDiffHelper.extract_baselines_at(comparison_base, base_dir, scheme, runner: runner)
       prefix = ApiDiffHelper.api_file_prefix(scheme)
       scheme_breaks = []
 
@@ -2554,11 +2556,16 @@ platform :ios do
 
     # Informational: a GitHub or Slack outage must not decide whether the gate fails.
     begin
-      announcement = notify_api_changes_on_slack(
-        reports_by_target: reports_by_target,
-        breaks: all_breaks,
-        labels: labels
-      )
+      # Announcing only from main keeps the feed to one post per change.
+      announcement = if on_main
+                       notify_api_changes_on_slack(
+                         reports_by_target: reports_by_target,
+                         breaks: all_breaks,
+                         labels: labels
+                       )
+                     else
+                       { fingerprint: nil, notice: nil }
+                     end
       schemes.each do |scheme|
         upsert_api_diff_comment(
           scheme: scheme,
@@ -2578,7 +2585,12 @@ platform :ios do
     end
 
     if ApiDiffHelper.gate_blocked?(all_breaks, labels)
-      UI.user_error!("Breaking public API changes detected. Add #{ApiDiffHelper::BREAKING_CHANGE_LABEL} if intentional.")
+      # main has no PR to read the label from, and the PR run already gated the change.
+      if on_main
+        UI.important("Breaking public API changes on main, already gated on the PR run")
+      else
+        UI.user_error!("Breaking public API changes detected. Add #{ApiDiffHelper::BREAKING_CHANGE_LABEL} if intentional.")
+      end
     end
   end
 
@@ -2645,7 +2657,7 @@ platform :ios do
     bot_token = ENV["SLACK_ACCESS_TOKEN_CIRCLE_CI_NOTIFY_ORB_IOS"]
     channel = ENV["SLACK_CHANNEL_SDK_NEW_API"]
 
-    source = api_gate_pr_link
+    source = api_gate_commit_link
     modules = ApiDiffHelper.changed_modules(options[:reports_by_target])
 
     summary = ApiDiffHelper.slack_summary(
@@ -2702,11 +2714,12 @@ platform :ios do
     comment ? comment["body"].to_s : ""
   end
 
-  private_lane :api_gate_pr_link do
-    pr_number = detect_pr_number
-    next "" if pr_number.nil?
+  # The commit page carries the PR link, and its sha is what tells a rerun it already announced.
+  private_lane :api_gate_commit_link do
+    sha = sh("git", "rev-parse", "HEAD", log: false).strip
+    next "" if sha.empty?
 
-    "<https://github.com/RevenueCat/#{REPO_NAME}/pull/#{pr_number}|##{pr_number}>"
+    "<https://github.com/RevenueCat/#{REPO_NAME}/commit/#{sha}|#{sha[0, 7]}>"
   end
 
 

fastlane/api_diff_helper.rb

@@ -297,7 +297,27 @@ def api_changes_reported?(output)
     !output.to_s.include?(NO_CHANGES_MARKER)
   end
 
-  MERGE_BASE_SWIFTINTERFACE_DIR = "/tmp/merge-base-swiftinterface".freeze
+  BASE_SWIFTINTERFACE_DIR = "/tmp/comparison-base-swiftinterface".freeze
+
+  MAIN_BRANCH = "main".freeze
+
+  def main_branch?(branch)
+    branch.to_s.strip == MAIN_BRANCH
+  end
+
+  def current_branch(runner:)
+    branch = ENV["CIRCLE_BRANCH"].to_s.strip
+    return branch unless branch.empty?
+
+    runner.call("git", "rev-parse", "--abbrev-ref", "HEAD").to_s.strip
+  end
+
+  # On main the merge base is HEAD, so HEAD^ is what the merge replaced.
+  def resolve_comparison_base(runner:, branch:)
+    return resolve_previous_commit(runner: runner) if main_branch?(branch)
+
+    resolve_merge_base(runner: runner)
+  end
 
   # The PR's own baselines match the generated files once regenerated, erasing the evidence.
   def resolve_merge_base(runner:)
@@ -307,6 +327,13 @@ def resolve_merge_base(runner:)
     sha
   end
 
+  def resolve_previous_commit(runner:)
+    sha = runner.call("git", "rev-parse", "HEAD^").to_s.strip
+    raise "Could not resolve the commit before HEAD" if sha.empty?
+
+    sha
+  end
+
   def extract_baselines_at(sha, destination_dir, scheme, runner:)
     FileUtils.mkdir_p(destination_dir)
     prefix = api_file_prefix(scheme)
@@ -743,11 +770,11 @@ def unbroken_modifications(modifications, breaks)
   def slack_summary(breaks, labels, source:, new_declarations: [], modules: [], modifications: [])
     changed = unbroken_modifications(modifications, breaks)
     headline = if breaks.any?
-                 gate_blocked?(breaks, labels) ? ":warning: *Breaking public API changes*" : ":warning: *Breaking public API changes* (allowed by label)"
+                 gate_blocked?(breaks, labels) ? ":warning: *Breaking public API landed on main*" : ":warning: *Breaking public API landed on main* (allowed by label)"
                elsif new_declarations.any?
-                 ":sparkles: *New public API*"
+                 ":sparkles: *New public API landed on main*"
                else
-                 ":pencil2: *Public API changed*"
+                 ":pencil2: *Public API changed on main*"
                end
     headline = [headline, announcement_identity(modules)].join(" · ")
 

fastlane/api_diff_helper_test.rb

@@ -409,6 +409,52 @@ def test_resolve_merge_base_raises_when_empty
     assert_match(/merge base/, error.message)
   end
 
+  def test_current_branch_prefers_the_ci_variable
+    with_circle_branch("main") do
+      assert_equal "main", ApiDiffHelper.current_branch(runner: ->(*_c) { "detached\n" })
+    end
+  end
+
+  def test_current_branch_falls_back_to_git
+    with_circle_branch(nil) do
+      runner = ->(*command) { command == ["git", "rev-parse", "--abbrev-ref", "HEAD"] ? "my-branch\n" : "" }
+
+      assert_equal "my-branch", ApiDiffHelper.current_branch(runner: runner)
+    end
+  end
+
+  # On main the merge base is HEAD, so reusing it would compare the commit against itself.
+  def test_comparison_base_on_main_is_the_previous_commit
+    runner = lambda do |*command|
+      case command
+      when ["git", "rev-parse", "HEAD^"] then "prevsha\n"
+      when ["git", "merge-base", "origin/main", "HEAD"] then "headsha\n"
+      end
+    end
+
+    assert_equal "prevsha", ApiDiffHelper.resolve_comparison_base(runner: runner, branch: "main")
+  end
+
+  def test_comparison_base_off_main_stays_the_merge_base
+    runner = lambda do |*command|
+      case command
+      when ["git", "rev-parse", "HEAD^"] then "prevsha\n"
+      when ["git", "merge-base", "origin/main", "HEAD"] then "forksha\n"
+      end
+    end
+
+    ["my-branch", "release/5.86.0", "gh-readonly-queue/main/pr-1-abc"].each do |branch|
+      assert_equal "forksha", ApiDiffHelper.resolve_comparison_base(runner: runner, branch: branch)
+    end
+  end
+
+  # A root commit would otherwise diff the whole API in as new.
+  def test_previous_commit_raises_when_empty
+    error = assert_raises(RuntimeError) { ApiDiffHelper.resolve_previous_commit(runner: ->(*_c) { "\n" }) }
+
+    assert_match(/before HEAD/, error.message)
+  end
+
   def test_extract_baselines_writes_one_file_per_platform
     Dir.mktmpdir do |dir|
       runner = ->(*command) { "public func fromMergeBase()\n// #{command.last}\n" }
@@ -1333,15 +1379,15 @@ def test_slack_summary_leads_with_breaks_when_there_are_any
 
     message = ApiDiffHelper.slack_summary(breaks, [], source: "<url|#42> Some PR", new_declarations: ["public func a()"])
 
-    assert message.start_with?(":warning: *Breaking public API changes*")
+    assert message.start_with?(":warning: *Breaking public API landed on main*")
     assert_includes message, "<url|#42> Some PR"
     assert_includes message, "1 potential break"
   end
 
   def test_slack_summary_leads_with_new_api_when_nothing_breaks
     message = ApiDiffHelper.slack_summary([], [], source: "<url|#42> Some PR", new_declarations: ["public func a()", "public var b: Swift.Int"])
 
-    assert message.start_with?(":sparkles: *New public API*")
+    assert message.start_with?(":sparkles: *New public API landed on main*")
     assert_includes message, "2 new declarations"
   end
 
@@ -1689,7 +1735,7 @@ def test_slack_summary_reports_an_attribute_only_modification
 
     message = ApiDiffHelper.slack_summary([], [], source: "<url|#7439>", modules: ["RevenueCat"], modifications: modifications)
 
-    assert message.start_with?(":pencil2: *Public API changed* · iOS :ios: · `RevenueCat`")
+    assert message.start_with?(":pencil2: *Public API changed on main* · iOS :ios: · `RevenueCat`")
     assert_includes message, "1 modification"
     assert_includes message, "~ added @available(*, deprecated…): "
     assert_includes message, "purchaseDate(forEntitlement"
@@ -1726,7 +1772,7 @@ def test_slack_summary_still_leads_with_new_api_when_something_was_added
       [], [], source: "", new_declarations: ["public func a()"], modules: ["RevenueCat"], modifications: modifications
     )
 
-    assert message.start_with?(":sparkles: *New public API*")
+    assert message.start_with?(":sparkles: *New public API landed on main*")
     assert_includes message, "1 new declaration, 1 modification"
     assert_includes message, "+ public func a()"
     assert_includes message, "~ added @available"
@@ -1735,7 +1781,7 @@ def test_slack_summary_still_leads_with_new_api_when_something_was_added
   def test_slack_summary_labels_the_platform_and_modules
     message = ApiDiffHelper.slack_summary([], [], source: "<url|#42>", new_declarations: ["public func a()"], modules: ["RevenueCatUI"])
 
-    assert message.start_with?(":sparkles: *New public API* · iOS :ios: · `RevenueCatUI`")
+    assert message.start_with?(":sparkles: *New public API landed on main* · iOS :ios: · `RevenueCatUI`")
   end
 
   def test_changed_modules_names_only_the_schemes_that_changed
@@ -1835,8 +1881,51 @@ def test_the_announcement_happens_before_the_comment_is_written
   end
 
 
+  # A rerun of the same main job must not post twice, and last_announcement bails on an empty
+  # source, so the commit link is what keeps the suppression alive.
+  def test_the_announcement_source_is_the_commit
+    lane = File.read(File.expand_path("Fastfile", __dir__))
+    link = lane[/private_lane :api_gate_commit_link do.*?\n  end\n/m]
+
+    refute_nil link, "the api_gate_commit_link lane moved; update this test"
+    assert_match(%r{/commit/}, link, "the message links the commit, not the PR")
+    assert_match(/next "" if sha\.empty\?/, link)
+    refute_match(/detect_pr_number/, lane[/source = api_gate_commit_link/] || "x")
+  end
+
+  # The feed was noisy because every PR run posted. Only main does now, so each change lands once.
+  def test_slack_is_announced_only_on_main
+    lane = File.read(File.expand_path("Fastfile", __dir__))
+    announce = lane[/announcement = if on_main.*?\n                     end\n/m]
+
+    refute_nil announce, "the Slack announcement is no longer gated on main; update this test"
+    assert_match(/notify_api_changes_on_slack/, announce)
+    assert_match(/\{ fingerprint: nil, notice: nil \}/, announce,
+                 "a PR run still needs an announcement shape for the comment")
+  end
+
+  # main carries no PR to hold the label, so the gate there would fail changes the PR approved.
+  def test_the_breaking_change_gate_cannot_redden_main
+    lane = File.read(File.expand_path("Fastfile", __dir__))
+    gate = lane[/if ApiDiffHelper\.gate_blocked\?.*?\n    end\n/m]
+
+    refute_nil gate, "the gate section of check_api_changes moved; update this test"
+    assert_match(/if on_main/, gate, "main must not fail the gate")
+    assert_operator gate.index("if on_main"), :<, gate.index("UI.user_error!"),
+                    "the main branch of the gate must come before the failure"
+  end
+
+
   # --- Attribute additions: allowlist, not denylist ---
 
+  def with_circle_branch(value)
+    previous = ENV["CIRCLE_BRANCH"]
+    ENV["CIRCLE_BRANCH"] = value
+    yield
+  ensure
+    ENV["CIRCLE_BRANCH"] = previous
+  end
+
   def modification_adding(attribute)
     "// From\npublic func f()\n\n// To\npublic func f()\n\n/**\nChanges:\n- Added attribute `#{attribute}`\n*/"
   end