feat(rules): ast-grep YAML for go-concurrency/channel-closed-by-sender-only

docs/go-concurrency-patterns.md

@@ -110,7 +110,7 @@ func process(ctx context.Context) error {
 
 **Owner**: go-architecture-assistant
 **Applies when**: a Go file calls `close(ch)` on a channel that was passed in as a function parameter from elsewhere — i.e. closed by a consumer/receiver rather than by the goroutine that produces values into it.
-**Enforcement**: judgment (ast-grep follow-up: `close(X)` where `X` is a parameter type `chan T` or `chan<- T`; the agent rules in whether the function is the producer or consumer based on whether it sends into `X`)
+**Enforcement**: `rules/go/channel-closed-by-sender-only.yml` flags every `close($X)` call. The agent decides per-finding whether the enclosing function is the producer (sends into the channel — close correct, often `defer close(ch)`) or a consumer (only receives — `close(ch)` is the bug), and clears multi-producer cases routed through a dedicated closer goroutine + sync.WaitGroup. The producer-vs-consumer judgment needs reading the function body's send/receive direction — exactly the cross-context reasoning ast-grep can't do reliably.
 **Why**: Closing a channel from the receiver side is a textbook race — the sender may still be writing when the close happens, producing `send on closed channel` panic. The Go convention is: **the producer owns the channel and is the only one allowed to close it.** Receivers learn of "no more values" via `for v := range ch` or the `comma-ok` idiom (`v, ok := <-ch`), never by closing themselves. Multi-producer cases use `sync.WaitGroup` + a single dedicated closer goroutine, not concurrent closes (which also panic).
 
 #### Bad

rules/go/channel-closed-by-sender-only.yml

@@ -0,0 +1,27 @@
+id: go-concurrency/channel-closed-by-sender-only
+language: go
+severity: error
+message: |
+ `close(ch)` call needs a producer-only owner. Closing a channel
+ from the receiver side races against any still-pending send and
+ panics `send on closed channel`. The Go convention is: producer
+ owns the channel and is the only one allowed to close it;
+ receivers use `for v := range ch` or the comma-ok idiom.
+ The agent decides per-finding whether the enclosing function is
+ the producer (sends into the channel — close is correct, often
+ `defer close(ch)`) or a consumer (only receives — `close(ch)` is
+ the bug). The agent also clears multi-producer cases that route
+ through a single dedicated closer goroutine + sync.WaitGroup.
+ See docs/go-concurrency-patterns.md
+ (RULE go-concurrency/channel-closed-by-sender-only).
+rule:
+ # Match every `close($X)` call. The producer-vs-consumer
+ # adjudication needs reading the enclosing function body's
+ # send/receive direction on $X — exactly the cross-context
+ # reasoning ast-grep can't do reliably.
+ pattern: 'close($X)'
+ignores:
+ - "**/*_test.go"
+ - "vendor/**"
+ - "**/vendor/**"
+ - "**/mocks/**"

rules/index.json

@@ -228,7 +228,7 @@
  "anchor": "go-concurrency/channel-closed-by-sender-only",
  "applies_when": "a Go file calls `close(ch)` on a channel that was passed in as a function parameter from elsewhere — i.e. closed by a consumer/receiver rather than by the goroutine that produces values into it.",
  "doc_path": "docs/go-concurrency-patterns.md",
- "enforcement": "judgment (ast-grep follow-up: `close(X)` where `X` is a parameter type `chan T` or `chan<- T`; the agent rules in whether the function is the producer or consumer based on whether it sends into `X`)",
+ "enforcement": "`rules/go/channel-closed-by-sender-only.yml` flags every `close($X)` call. The agent decides per-finding whether the enclosing function is the producer (sends into the channel — close correct, often `defer close(ch)`) or a consumer (only receives — `close(ch)` is the bug), and clears multi-producer cases routed through a dedicated closer goroutine + sync.WaitGroup. The producer-vs-consumer judgment needs reading the function body's send/receive direction — exactly the cross-context reasoning ast-grep can't do reliably.",
  "id": "go-concurrency/channel-closed-by-sender-only",
  "level": "MUST",
  "owner": "go-architecture-assistant"