Add new scripts and targets

Author: stuartmorgan-g

.ci.yaml

@@ -228,6 +228,24 @@ targets:
       channel: stable
       version_file: flutter_stable.version
 
+  # Analyze with the previous stable (N-1) and the stable before that (N-2). The
+  # versions in `channel` should be updated after a new major stable release.
+  - name: Linux analyze_legacy N-1
+    bringup: true # New target
+    recipe: packages/packages
+    timeout: 30
+    properties:
+      target_file: analyze_legacy.yaml
+      channel: "3.7.12"
+
+  - name: Linux analyze_legacy N-2
+    bringup: true # New target
+    recipe: packages/packages
+    timeout: 30
+    properties:
+      target_file: analyze_legacy.yaml
+      channel: "3.3.10"
+
   - name: Linux_android custom_package_tests master
     recipe: packages/packages
     timeout: 30

.ci/scripts/analyze_legacy.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+set -e
+
+# Allow analyzing packages that use a dev dependency with a higher minimum
+# Flutter/Dart version than the package itself. Non-client code doesn't need to
+# work in legacy versions.
+#
+# This requires the --lib-only flag below.
+./script/tool_runner.sh remove-dev-dependencies
+
+# This uses --run-on-dirty-packages rather than --packages-for-branch
+# since only the packages changed by 'make-deps-path-based' need to be
+# re-checked.
+./script/tool_runner.sh analyze --lib-only \
+    --skip-if-not-supporting-flutter-version="$CHANNEL" \
+    --custom-analysis=script/configs/custom_analysis.yaml
+
+# Restore the tree to a clean state, to avoid accidental issues if
+# other script steps are added to the enclosing task.
+git checkout .

.ci/scripts/pathified_analyze.sh renamed to .ci/scripts/analyze_pathified.sh

@@ -12,4 +12,4 @@ tasks:
     # the changes won't break analysis of other packages in the respository
     # that depend on it.
   - name: analyze - pathified
-    script: .ci/scripts/pathified_analyze.sh
+    script: .ci/scripts/analyze_pathified.sh

.ci/scripts/dart_unit_tests_pathified.sh

@@ -0,0 +1,11 @@
+tasks:
+  - name: prepare tool
+    script: .ci/scripts/prepare_tool.sh
+  # Does a sanity check that packages at least pass analysis on the N-1 and N-2
+  # versions of Flutter stable if the package claims to support that version.
+  # This is to minimize accidentally making changes that break old versions
+  # (which we don't commit to supporting, but don't want to actively break)
+  # without updating the constraints.
+  # See https://github.com/flutter/flutter/wiki/Contributing-to-Plugins-and-Packages#supported-flutter-versions
+  - name: analyze - downgraded
+    script: .ci/scripts/analyze_legacy.sh

.ci/targets/analyze.yaml

@@ -10,7 +10,7 @@ tasks:
     args: ["license-check"]
     always: true
     # The major and minor version here should match the lowest version analyzed
-    # in legacy version analysis (currently .cirrus.yaml legacy_version_analyze).
+    # in legacy version analysis (.ci.yaml analyze_legacy).
   - name: pubspec validation
     script: script/tool_runner.sh
     args: