[IMP] runbot_merge: add optional statuses on PRs

If a status is defined as `optional`, then the PR is considered valid
if the status is never sent, but *if* the status is sent then it
becomes required.

Note that as ever this is a per-commit requirement, so it's mostly
useful for conditional statuses.

Fixes #1062

runbot_merge/__manifest__.py

@@ -1,6 +1,6 @@
 {
     'name': 'merge bot',
-    'version': '1.15',
+    'version': '1.16',
     'depends': ['contacts', 'mail', 'website'],
     'data': [
         'security/security.xml',

runbot_merge/migrations/17.0.1.16/pre-migrations.py

@@ -0,0 +1,12 @@
+def migrate(cr, _version):
+    cr.execute("""
+ALTER TABLE runbot_merge_repository_status
+    ALTER COLUMN prs TYPE varchar;
+
+UPDATE runbot_merge_repository_status
+    SET prs =
+        CASE prs
+            WHEN 'true' THEN 'required'
+            ELSE 'ignored'
+        END;
+    """)

runbot_merge/models/pull_requests.py

@@ -10,6 +10,7 @@
 import logging
 import re
 import time
+import typing
 from enum import IntEnum
 from functools import reduce
 from operator import itemgetter
@@ -42,9 +43,33 @@ class StatusConfiguration(models.Model):
     context = fields.Char(required=True)
     repo_id = fields.Many2one('runbot_merge.repository', required=True, ondelete='cascade')
     branch_filter = fields.Char(help="branches this status applies to")
-    prs = fields.Boolean(string="Applies to pull requests", default=True)
+    prs = fields.Selection([
+        ('required', 'Required'),
+        ('optional', 'Optional'),
+        ('ignored', 'Ignored'),
+    ],
+        default='required',
+        required=True,
+        string="Applies to pull requests",
+        column_type=enum(_name, 'prs'),
+    )
     stagings = fields.Boolean(string="Applies to stagings", default=True)
 
+    def _auto_init(self):
+        for field in self._fields.values():
+            if not isinstance(field, fields.Selection) or field.column_type[0] == 'varchar':
+                continue
+
+            t = field.column_type[1]
+            self.env.cr.execute("SELECT 1 FROM pg_type WHERE typname = %s", [t])
+            if not self.env.cr.rowcount:
+                self.env.cr.execute(
+                    f"CREATE TYPE {t} AS ENUM %s",
+                    [tuple(s for s, _ in field.selection)]
+                )
+
+        super()._auto_init()
+
     def _for_branch(self, branch):
         assert branch._name == 'runbot_merge.branch', \
             f'Expected branch, got {branch}'
@@ -55,12 +80,16 @@ def _for_branch(self, branch):
     def _for_pr(self, pr):
         assert pr._name == 'runbot_merge.pull_requests', \
             f'Expected pull request, got {pr}'
-        return self._for_branch(pr.target).filtered('prs')
+        return self._for_branch(pr.target).filtered(lambda p: p.prs != 'ignored')
     def _for_staging(self, staging):
         assert staging._name == 'runbot_merge.stagings', \
             f'Expected staging, got {staging}'
         return self._for_branch(staging.target).filtered('stagings')
 
+    @property
+    def _default_pr_state(self) -> typing.Literal['pending', 'success']:
+        return 'pending' if self.prs == 'required' else 'success'
+
 class Repository(models.Model):
     _name = _description = 'runbot_merge.repository'
     _order = 'sequence, id'
@@ -1243,7 +1272,7 @@ def _compute_statuses(self):
 
             st = 'success'
             for ci in pr.repository.status_ids._for_pr(pr):
-                v = (statuses.get(ci.context) or {'state': 'pending'})['state']
+                v = (statuses.get(ci.context) or {'state': ci._default_pr_state})['state']
                 if v in ('error', 'failure'):
                     st = 'failure'
                     break

runbot_merge/tests/test_by_branch.py

@@ -14,7 +14,7 @@ def _setup_statuses(project, repo):
             'branch_filter': [('id', '=', project.branch_ids.id)]
         }),
         (0, 0, {'context': 'pr', 'stagings': False}),
-        (0, 0, {'context': 'staging', 'prs': False}),
+        (0, 0, {'context': 'staging', 'prs': 'ignored'}),
     ]
 
 @pytest.mark.usefixtures('_setup_statuses')

runbot_merge/tests/test_statuses_optional.py

@@ -0,0 +1,49 @@
+from utils import Commit, to_pr
+
+
+def test_basic(env, project, make_repo, users, setreviewers, config):
+    repository = make_repo('repo')
+    env['runbot_merge.repository'].create({
+        'project_id': project.id,
+        'name': repository.name,
+        'status_ids': [(0, 0, {'context': 'l/int', 'prs': 'optional'})]
+    })
+    setreviewers(*project.repo_ids)
+    env['runbot_merge.events_sources'].create({'repository': repository.name})
+
+    with repository:
+        m = repository.make_commits(None, Commit('root', tree={'a': '1'}), ref='heads/master')
+
+        repository.make_commits(m, Commit('pr', tree={'a': '2'}), ref='heads/change')
+        pr = repository.make_pr(target='master', title='super change', head='change')
+    env.run_crons()
+
+    # if an optional status is never received then the PR is valid
+    pr_id = to_pr(env, pr)
+    assert pr_id.state == 'validated'
+
+    # If a run has started, then the PR is pending (not considered valid), this
+    # limits the odds of merging a PR even though it's not valid, as long as the
+    # optional status starts running before all the required statuses arrive
+    # (with a success result).
+    with repository:
+        repository.post_status(pr.head, 'pending', 'l/int')
+    env.run_crons()
+    assert pr_id.state == 'opened'
+
+    # If the status fails, then the PR is rejected.
+    with repository:
+        repository.post_status(pr.head, 'failure', 'l/int')
+    env.run_crons()
+    assert pr_id.state == 'opened'
+
+    # re-run the job / fix the PR
+    with repository:
+        repository.post_status(pr.head, 'pending', 'l/int')
+    env.run_crons()
+    assert pr_id.state == 'opened'
+
+    with repository:
+        repository.post_status(pr.head, 'success', 'l/int')
+    env.run_crons()
+    assert pr_id.state == 'validated'