Reduce number of CI jobs run on PRs (#13713)

* Reduce number of CI jobs run on PRs

* Newsfile

* Also limit sytest jobs

* Fix typo

* Fix up

* Fixup

3 files changed, 160 insertions, 66 deletions

diff --git a/.ci/scripts/calculate_jobs.py b/.ci/scripts/calculate_jobs.py
new file mode 100755
index 0000000000..b1f604eeb0
--- /dev/null
+++ b/.ci/scripts/calculate_jobs.py
@@ -0,0 +1,128 @@
+#!/usr/bin/env python
+# Copyright 2022 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Calculate the trial jobs to run based on if we're in a PR or not.
+
+import json
+import os
+
+IS_PR = os.environ["GITHUB_REF"].startswith("refs/pull/")
+
+# First calculate the various trial jobs.
+#
+# For each type of test we only run on Py3.7 on PRs
+
+trial_sqlite_tests = [
+    {
+        "python-version": "3.7",
+        "database": "sqlite",
+        "extras": "all",
+    }
+]
+
+if not IS_PR:
+    trial_sqlite_tests.extend(
+        {
+            "python-version": version,
+            "database": "sqlite",
+            "extras": "all",
+        }
+        for version in ("3.8", "3.9", "3.10")
+    )
+
+
+trial_postgres_tests = [
+    {
+        "python-version": "3.7",
+        "database": "postgres",
+        "postgres-version": "10",
+        "extras": "all",
+    }
+]
+
+if not IS_PR:
+    trial_postgres_tests.append(
+        {
+            "python-version": "3.10",
+            "database": "postgres",
+            "postgres-version": "14",
+            "extras": "all",
+        }
+    )
+
+trial_no_extra_tests = [
+    {
+        "python-version": "3.7",
+        "database": "sqlite",
+        "extras": "",
+    }
+]
+
+print("::group::Calculated trial jobs")
+print(
+    json.dumps(
+        trial_sqlite_tests + trial_postgres_tests + trial_no_extra_tests, indent=4
+    )
+)
+print("::endgroup::")
+
+test_matrix = json.dumps(
+    trial_sqlite_tests + trial_postgres_tests + trial_no_extra_tests
+)
+print(f"::set-output name=trial_test_matrix::{test_matrix}")
+
+
+# First calculate the various sytest jobs.
+#
+# For each type of test we only run on focal on PRs
+
+
+sytest_tests = [
+    {
+        "sytest-tag": "focal",
+    },
+    {
+        "sytest-tag": "focal",
+        "postgres": "postgres",
+    },
+    {
+        "sytest-tag": "focal",
+        "postgres": "multi-postgres",
+        "workers": "workers",
+    },
+]
+
+if not IS_PR:
+    sytest_tests.extend(
+        [
+            {
+                "sytest-tag": "testing",
+                "postgres": "postgres",
+            },
+            {
+                "sytest-tag": "buster",
+                "postgres": "multi-postgres",
+                "workers": "workers",
+            },
+        ]
+    )
+
+
+print("::group::Calculated sytest jobs")
+print(json.dumps(sytest_tests, indent=4))
+print("::endgroup::")
+
+test_matrix = json.dumps(sytest_tests)
+print(f"::set-output name=sytest_test_matrix::{test_matrix}")
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 720cb13907..3ce4ffb036 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -73,63 +73,48 @@ jobs:
     steps:
       - run: "true"
 
-  trial:
+  calculate-test-jobs:
     if: ${{ !cancelled() && !failure() }} # Allow previous steps to be skipped, but not fail
     needs: linting-done
     runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+      - id: get-matrix
+        run: .ci/scripts/calculate_jobs.py
+    outputs:
+      trial_test_matrix: ${{ steps.get-matrix.outputs.trial_test_matrix }}
+      sytest_test_matrix: ${{ steps.get-matrix.outputs.sytest_test_matrix }}
+
+  trial:
+    if: ${{ !cancelled() && !failure() }} # Allow previous steps to be skipped, but not fail
+    needs: calculate-test-jobs
+    runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.7", "3.8", "3.9", "3.10"]
-        database: ["sqlite"]
-        extras: ["all"]
-        is_pr:
-          - ${{ startsWith(github.ref, 'refs/pull/') }}
-
-        # If we're a PR then we only test min and max python.
-        exclude:
-          - is_pr: true
-            python-version: 3.8
-          - is_pr: true
-            python-version: 3.9
-
-        include:
-          # Newest Python without optional deps
-          - python-version: "3.10"
-            extras: ""
-
-          # Oldest Python with PostgreSQL
-          - python-version: "3.7"
-            database: "postgres"
-            postgres-version: "10"
-            extras: "all"
-
-          # Newest Python with newest PostgreSQL
-          - python-version: "3.10"
-            database: "postgres"
-            postgres-version: "14"
-            extras: "all"
+        job:  ${{ fromJson(needs.calculate-test-jobs.outputs.trial_test_matrix) }}
 
     steps:
       - uses: actions/checkout@v2
       - run: sudo apt-get -qq install xmlsec1
-      - name: Set up PostgreSQL ${{ matrix.postgres-version }}
-        if: ${{ matrix.postgres-version }}
+      - name: Set up PostgreSQL ${{ matrix.job.postgres-version }}
+        if: ${{ matrix.job.postgres-version }}
         run: |
           docker run -d -p 5432:5432 \
             -e POSTGRES_PASSWORD=postgres \
             -e POSTGRES_INITDB_ARGS="--lc-collate C --lc-ctype C --encoding UTF8" \
-            postgres:${{ matrix.postgres-version }}
+            postgres:${{ matrix.job.postgres-version }}
       - uses: matrix-org/setup-python-poetry@v1
         with:
-          python-version: ${{ matrix.python-version }}
-          extras: ${{ matrix.extras }}
+          python-version: ${{ matrix.job.python-version }}
+          extras: ${{ matrix.job.extras }}
       - name: Await PostgreSQL
-        if: ${{ matrix.postgres-version }}
+        if: ${{ matrix.job.postgres-version }}
         timeout-minutes: 2
         run: until pg_isready -h localhost; do sleep 1; done
       - run: poetry run trial --jobs=2 tests
         env:
-          SYNAPSE_POSTGRES: ${{ matrix.database == 'postgres' || '' }}
+          SYNAPSE_POSTGRES: ${{ matrix.job.database == 'postgres' || '' }}
           SYNAPSE_POSTGRES_HOST: localhost
           SYNAPSE_POSTGRES_USER: postgres
           SYNAPSE_POSTGRES_PASSWORD: postgres
@@ -208,45 +193,25 @@ jobs:
 
   sytest:
     if: ${{ !failure() && !cancelled() }}
-    needs: linting-done
+    needs: calculate-test-jobs
     runs-on: ubuntu-latest
     container:
-      image: matrixdotorg/sytest-synapse:${{ matrix.sytest-tag }}
+      image: matrixdotorg/sytest-synapse:${{ matrix.job.sytest-tag }}
       volumes:
         - ${{ github.workspace }}:/src
       env:
         SYTEST_BRANCH: ${{ github.head_ref }}
-        POSTGRES: ${{ matrix.postgres && 1}}
-        MULTI_POSTGRES: ${{ (matrix.postgres == 'multi-postgres') && 1}}
-        WORKERS: ${{ matrix.workers && 1 }}
-        REDIS: ${{ matrix.redis && 1 }}
-        BLACKLIST: ${{ matrix.workers && 'synapse-blacklist-with-workers' }}
+        POSTGRES: ${{ matrix.job.postgres && 1}}
+        MULTI_POSTGRES: ${{ (matrix.job.postgres == 'multi-postgres') && 1}}
+        WORKERS: ${{ matrix.job.workers && 1 }}
+        REDIS: 1
+        BLACKLIST: ${{ matrix.job.workers && 'synapse-blacklist-with-workers' }}
         TOP: ${{ github.workspace }}
 
     strategy:
       fail-fast: false
       matrix:
-        include:
-          - sytest-tag: focal
-
-          - sytest-tag: focal
-            postgres: postgres
-
-          - sytest-tag: testing
-            postgres: postgres
-
-          - sytest-tag: focal
-            postgres: multi-postgres
-            workers: workers
-
-          - sytest-tag: buster
-            postgres: multi-postgres
-            workers: workers
-
-          - sytest-tag: buster
-            postgres: postgres
-            workers: workers
-            redis: redis
+        job: ${{ fromJson(needs.calculate-test-jobs.outputs.sytest_test_matrix) }}
 
     steps:
       - uses: actions/checkout@v2
@@ -262,7 +227,7 @@ jobs:
         uses: actions/upload-artifact@v2
         if: ${{ always() }}
         with:
-          name: Sytest Logs - ${{ job.status }} - (${{ join(matrix.*, ', ') }})
+          name: Sytest Logs - ${{ job.status }} - (${{ join(matrix.job.*, ', ') }})
           path: |
             /logs/results.tap
             /logs/**/*.log*
diff --git a/changelog.d/13713.misc b/changelog.d/13713.misc
new file mode 100644
index 0000000000..1044099542
--- /dev/null
+++ b/changelog.d/13713.misc
@@ -0,0 +1 @@
+Reduce number of CI checks we run for PRs.