ci: only test changed languages on pull requests

.github/workflows/hello-world.yml

@@ -4,11 +4,17 @@ on:
   push:
     branches: [master]
   pull_request:
+  schedule:
+    - cron: '0 4 * * *'
   workflow_dispatch:
 
 permissions:
   contents: read
 
+env:
+  # Pull requests only test the languages they change; master, the daily schedule and manual runs test everything.
+  HELLO_CHANGED_SINCE: ${{ github.event_name == 'pull_request' && format('origin/{0}', github.base_ref) || '' }}
+
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true
@@ -19,20 +25,26 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
       - run: python3 scripts/hello.py check
 
   base:
     name: Run (preinstalled toolchains)
     runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
       - run: python3 scripts/hello.py test --group base --strict
 
   apt:
     name: Run (apt toolchains)
     runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
       - name: Install toolchains
         run: |
           sudo apt-get update -qq
@@ -44,6 +56,8 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
       - uses: mlugg/setup-zig@v2
       - uses: dart-lang/setup-dart@v1
       - uses: crystal-lang/install-crystal@v1
@@ -65,6 +79,8 @@ jobs:
         shard: [1, 2, 3, 4]
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
       - run: python3 scripts/hello.py test --group docker --strict --shard ${{ matrix.shard }}/4 --timeout 600
         env:
           HELLO_DOCKER_MIRROR: mirror.gcr.io
@@ -74,6 +90,8 @@ jobs:
     runs-on: macos-latest
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
       - run: python3 scripts/hello.py test --group macos --strict
 
   windows:
@@ -84,4 +102,6 @@ jobs:
         shell: bash
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
       - run: python scripts/hello.py test --group windows --strict

README.md

@@ -620,6 +620,7 @@ Languages designed as jokes, puzzles or experiments.
 python3 scripts/hello.py check              # metadata, files and README are consistent
 python3 scripts/hello.py test               # run every language whose toolchain is installed locally
 python3 scripts/hello.py test --lang python --lang rust
+python3 scripts/hello.py test --changed-since origin/master   # only languages changed on this branch
 python3 scripts/hello.py readme             # regenerate this README from languages/*/meta.json
 ```
 

docs/specs/008-selective-ci/plan.md

@@ -0,0 +1,5 @@
+# Plano — 008
+
+- `git diff --name-only <ref>...HEAD` dentro do harness.
+- `actions/checkout` com `fetch-depth: 0` nos jobs de teste para ter a base do PR.
+- Variável `HELLO_CHANGED_SINCE` no workflow, vazia fora de PRs.

docs/specs/008-selective-ci/spec.md

@@ -0,0 +1,19 @@
+# 008 — CI seletivo nos PRs
+
+Issue: #5.
+
+## O quê
+Nos pull requests, executar só os testes das linguagens alteradas; a suíte completa roda nos pushes para `master`, num agendamento diário e sob demanda.
+
+## Requisitos
+1. `scripts/hello.py test --changed-since <ref>`: seleciona as linguagens com arquivos alterados em `languages/<slug>/` desde `<ref>`.
+2. Se `scripts/` ou `.github/workflows/` mudarem, todas as linguagens são testadas.
+3. Um grupo sem linguagens selecionadas passa sem executar nada.
+4. Workflow: `pull_request` usa `--changed-since` contra a base do PR; `push` em `master`, `schedule` (diário) e `workflow_dispatch` rodam tudo.
+
+## Critérios de aceite
+- Um PR que altera uma única linguagem executa só o teste dela.
+- O job `check` continua validando todos os metadados e o README.
+
+## Fora de escopo
+- Um job por linguagem (avaliado na issue #5; a seleção resolve o custo principal sem multiplicar jobs).

docs/specs/008-selective-ci/tasks.md

@@ -0,0 +1,5 @@
+# Tarefas — 008
+
+- [x] `--changed-since` no harness.
+- [x] Workflow com seleção em PRs e execução diária completa.
+- [x] Validar com um PR que toca uma linguagem.

docs/specs/ROADMAP.md

@@ -9,3 +9,4 @@
 | [005 — Ampliar a biblioteca de linguagens](005-more-languages/spec.md) | concluída | 003, 004 |
 | [006 — Ampliar a cobertura de testes](006-more-tests/spec.md) | concluída | 004 |
 | [007 — Cobertura de 80%](007-coverage-80/spec.md) | concluída | 006 |
+| [008 — CI seletivo nos PRs](008-selective-ci/spec.md) | concluída | 004 |

scripts/hello.py

@@ -171,6 +171,7 @@ def render_readme(langs):
 python3 scripts/hello.py check              # metadata, files and README are consistent
 python3 scripts/hello.py test               # run every language whose toolchain is installed locally
 python3 scripts/hello.py test --lang python --lang rust
+python3 scripts/hello.py test --changed-since origin/master   # only languages changed on this branch
 python3 scripts/hello.py readme             # regenerate this README from languages/*/meta.json
 ```
 
@@ -291,8 +292,26 @@ def normalize(text):
     return re.sub(r"[^a-z]", "", text.lower())
 
 
+def changed_slugs(ref):
+    """Slugs changed since ref, or None when tooling changed and everything must run."""
+    out = subprocess.run(["git", "diff", "--name-only", "%s...HEAD" % ref], cwd=ROOT, check=True,
+                         stdout=subprocess.PIPE).stdout.decode()
+    slugs = set()
+    for path in out.split():
+        if path.startswith(("scripts/", ".github/workflows/")):
+            return None
+        if path.startswith("languages/"):
+            slugs.add(path.split("/")[1])
+    return slugs
+
+
 def cmd_test(args):
     langs = [l for l in load_languages() if l.get("test")]
+    if args.changed_since:
+        slugs = changed_slugs(args.changed_since)
+        if slugs is not None:
+            langs = [l for l in langs if l["slug"] in slugs]
+            print("Testing languages changed since %s: %s" % (args.changed_since, ", ".join(sorted(slugs)) or "none"))
     if args.group:
         langs = [l for l in langs if l["test"]["group"] == args.group]
     if args.lang:
@@ -367,7 +386,10 @@ def cmd_test(args):
 
 def cmd_apt(args):
     pkgs = set()
+    slugs = changed_slugs(args.changed_since) if args.changed_since else None
     for l in load_languages():
+        if slugs is not None and l["slug"] not in slugs:
+            continue
         t = l.get("test")
         if t and (not args.group or t["group"] == args.group):
             pkgs.update(t.get("apt", []))
@@ -385,8 +407,11 @@ def main():
     t.add_argument("--strict", action="store_true", help="fail when a toolchain is missing")
     t.add_argument("--timeout", type=int, default=180)
     t.add_argument("--shard", help="run only shard I of N, as I/N")
+    t.add_argument("--changed-since", default=os.environ.get("HELLO_CHANGED_SINCE") or None,
+                   help="only languages changed since this git ref (all when scripts/ or workflows change)")
     a = sub.add_parser("apt-packages")
     a.add_argument("--group", choices=TEST_GROUPS)
+    a.add_argument("--changed-since", default=os.environ.get("HELLO_CHANGED_SINCE") or None)
     args = p.parse_args()
     return {"readme": cmd_readme, "check": cmd_check, "test": cmd_test, "apt-packages": cmd_apt}[args.cmd](args) or 0