watchpr: arm the conflict rule on a new merge computation

A mergeable=false baseline meant a conflict could never be reported, since
Gitea sends false while it recomputes after a push. Arm on a head or base SHA
change as well as on a mergeable poll, break the conflict run on unknown and
failed polls, and print the baseline with the conditions it suppresses.
This commit is contained in:
2026-09-26 20:48:31 +10:00
parent 6988be9ff3
commit 54c1d868d3
5 changed files with 346 additions and 43 deletions
+54 -28
View File
@@ -17,9 +17,11 @@ func IsPRGone(err error) bool {
return errors.Is(err, errPRGone)
}
// Mergeability is Gitea's mergeable flag as a tri-state. The flag is null or
// absent while Gitea recomputes the merge base, and an unknown value must not be
// read as either answer.
// Mergeability is Gitea's mergeable flag. Gitea 1.26 always sends a plain bool,
// and sends false both for a real conflict and while it recomputes the merge
// base after a push, so false on its own decides nothing (prWatch resolves it).
// Unknown covers what the bool cannot carry: an absent or null flag from another
// Gitea build, and a snapshot no successful poll ever filled in.
type Mergeability int
const (
@@ -68,6 +70,7 @@ type PRState struct {
State string `json:"state"` // open / closed
Merged bool `json:"merged"`
HeadSHA string `json:"head_sha"`
BaseSHA string `json:"base_sha"`
Mergeable Mergeability `json:"mergeable"`
CIStatus string `json:"ci_status"` // success / pending / failure / error / ""
NonAgentComments int `json:"non_agent_comments"`
@@ -101,6 +104,7 @@ func FetchState(c *GiteaClient, ref PRRef, agentLogin string) (PRState, error) {
State: pr.State,
Merged: pr.Merged,
HeadSHA: pr.Head.Sha,
BaseSHA: pr.Base.Sha,
Mergeable: pr.Mergeable,
CIStatus: ci,
NonAgentComments: countNonAgentComments(comments, agentLogin),
@@ -141,48 +145,67 @@ func terminalState(st PRState) (bool, string) {
return false, ""
}
// conflictPolls is how many consecutive non-mergeable polls confirm a real
// conflict. Gitea reports mergeable=false while it recomputes the merge base
// after a push, so a single poll is debounced.
// conflictPolls is how many consecutive non-mergeable polls of an unchanged
// merge computation confirm a real conflict.
const conflictPolls = 2
// prWatch tracks one PR across polls. Mergeability needs more memory than the
// previous snapshot: losing it only counts as a change if the PR was mergeable
// at some point after watching began, since a conflict that predates the
// baseline is the state the operator is already waiting on.
// prWatch tracks one PR across polls, because mergeability needs more memory
// than the previous snapshot. Gitea reports mergeable=false while it recomputes
// the merge base after a push, so a false is only trusted once this watch has
// seen a merge computation start: the PR was mergeable at some point, or its
// head or base SHA moved. A bare false inherited from the baseline says nothing
// -- it is equally a conflict the operator is already waiting on and a recompute
// in flight -- so it arms nothing.
type prWatch struct {
prev PRState
everMergeable bool
conflicts int
prev PRState
armed bool
conflicts int
}
func newPRWatch(baseline PRState) *prWatch {
w := &prWatch{prev: baseline}
w.track(baseline)
return w
return &prWatch{prev: baseline, armed: baseline.Mergeable == MergeYes}
}
// track folds one snapshot's mergeability into the run of observations. Unknown
// neither confirms a conflict nor clears one.
// mergeInputsChanged reports whether the commits Gitea merges have moved, which
// starts a fresh merge computation whose result is attributable to this watch.
func mergeInputsChanged(prev, cur PRState) bool {
return cur.HeadSHA != prev.HeadSHA || cur.BaseSHA != prev.BaseSHA
}
// track folds one snapshot's mergeability into the run of observations. The
// polls that confirm a conflict must be adjacent, so anything but another
// non-mergeable observation breaks the run.
func (w *prWatch) track(st PRState) {
switch st.Mergeable {
case MergeYes:
w.everMergeable = true
w.conflicts = 0
case MergeNo:
w.conflicts++
case MergeYes:
w.armed = true
w.conflicts = 0
default:
w.conflicts = 0
}
}
// missed records a poll that never produced a snapshot; the run of adjacent
// non-mergeable observations does not survive the gap.
func (w *prWatch) missed() {
w.conflicts = 0
}
// observe folds in the newest snapshot and reports whether the watch should end.
func (w *prWatch) observe(cur PRState) (bool, string) {
changed, reason := MeaningfulChange(w.prev, cur)
if mergeInputsChanged(w.prev, cur) {
w.armed = true
w.conflicts = 0
}
w.prev = cur
w.track(cur)
if changed {
return true, reason
}
if w.everMergeable && w.conflicts >= conflictPolls && cur.State == "open" {
if w.armed && w.conflicts >= conflictPolls && cur.State == "open" {
return true, "PR lost mergeability (conflict)"
}
return false, ""
@@ -202,10 +225,11 @@ const MaxPollFailures = 20
// is gone, renamed, or no longer visible), and MaxPollFailures consecutive
// failures of one PR all abort, because a watcher that sees nothing must not
// look healthy.
// onBaseline, if set, fires once after all baselines are captured and before the
// first tick.
func Watch(f StateFetcher, refs []PRRef, agentLogin string, ticks <-chan time.Time, onBaseline func(), onError func(PRRef, error)) (WatchResult, error) {
// onBaseline, if set, receives every captured baseline once, before the first
// tick, so a caller can show what state the watch started from.
func Watch(f StateFetcher, refs []PRRef, agentLogin string, ticks <-chan time.Time, onBaseline func([]PRState), onError func(PRRef, error)) (WatchResult, error) {
watches := make(map[string]*prWatch, len(refs))
baselines := make([]PRState, 0, len(refs))
for _, ref := range refs {
st, err := f.FetchState(ref, agentLogin)
if err != nil {
@@ -215,9 +239,10 @@ func Watch(f StateFetcher, refs []PRRef, agentLogin string, ticks <-chan time.Ti
return WatchResult{Ref: ref, Reason: reason, State: st}, nil
}
watches[ref.String()] = newPRWatch(st)
baselines = append(baselines, st)
}
if onBaseline != nil {
onBaseline()
onBaseline(baselines)
}
fails := make(map[string]int, len(refs))
for range ticks {
@@ -229,6 +254,7 @@ func Watch(f StateFetcher, refs []PRRef, agentLogin string, ticks <-chan time.Ti
return WatchResult{}, fmt.Errorf("polling %s: %w", key, err)
}
fails[key]++
watches[key].missed()
if onError != nil {
onError(ref, err)
}
@@ -265,8 +291,8 @@ func isFailedCI(state string) bool {
// MeaningfulChange compares a previous state to the current one and reports
// whether a change warrants alerting the operator, with a human-readable
// reason. Benign transitions (CI pending→success, the agent's own comments, a
// new head commit, an unchanged snapshot) return false. Mergeability is not
// decided here: it takes a whole run of observations, which prWatch keeps.
// new head or base commit, an unchanged snapshot) return false. Mergeability is
// not decided here: it takes a whole run of observations, which prWatch keeps.
//
// Alerting conditions:
// - the PR merged