go/analysis/passes/lostcancel: add WithCancelCause et al

The *Cause variants behave in a similar manner.

Updates golang/go#70185

Change-Id: Ia7eea7a5be8878930505b63fa8222060fef47079
Reviewed-on: https://go-review.googlesource.com/c/tools/+/625115
Reviewed-by: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Alan Donovan <adonovan@google.com>

Author: adonovan

go/analysis/passes/lostcancel/doc.go

@@ -10,7 +10,7 @@
 // lostcancel: check cancel func returned by context.WithCancel is called
 //
 // The cancellation function returned by context.WithCancel, WithTimeout,
-// and WithDeadline must be called or the new context will remain live
-// until its parent context is cancelled.
+// WithDeadline and variants such as WithCancelCause must be called,
+// or the new context will remain live until its parent context is cancelled.
 // (The background context is never cancelled.)
 package lostcancel

go/analysis/passes/lostcancel/lostcancel.go

@@ -198,7 +198,9 @@ func isContextWithCancel(info *types.Info, n ast.Node) bool {
 		return false
 	}
 	switch sel.Sel.Name {
-	case "WithCancel", "WithTimeout", "WithDeadline":
+	case "WithCancel", "WithCancelCause",
+		"WithTimeout", "WithTimeoutCause",
+		"WithDeadline", "WithDeadlineCause":
 	default:
 		return false
 	}

go/analysis/passes/lostcancel/testdata/src/typeparams/typeparams.go

@@ -8,17 +8,22 @@ package typeparams
 
 import (
 	"context"
+	"io"
 	"time"
 )
 
+//
+// These comment lines are ballast to ensure
+// that this is L17. Add/remove as needed.
+
 var bg = context.Background()
 
 func _[T any]() {
 	var _, cancel = context.WithCancel(bg) // want `the cancel function is not used on all paths \(possible context leak\)`
 	if false {
 		_ = cancel
 	}
-} // want "this return statement may be reached without using the cancel var defined on line 17"
+} // want "this return statement may be reached without using the cancel var defined on line 22"
 
 func _[T any]() {
 	_, cancel := context.WithCancel(bg)
@@ -55,3 +60,16 @@ func _() {
 	var x C[int]
 	x.f()
 }
+
+func withCancelCause(maybe bool) {
+	{
+		_, cancel := context.WithCancelCause(bg)
+		defer cancel(io.EOF) // ok
+	}
+	{
+		_, cancel := context.WithCancelCause(bg) // want "the cancel function is not used on all paths \\(possible context leak\\)"
+		if maybe {
+			cancel(io.EOF)
+		}
+	}
+} // want "this return statement may be reached without using the cancel var defined on line 70"

gopls/doc/analyzers.md

@@ -428,8 +428,8 @@ Package documentation: [loopclosure](https://pkg.go.dev/golang.org/x/tools/go/an
 
 
 The cancellation function returned by context.WithCancel, WithTimeout,
-and WithDeadline must be called or the new context will remain live
-until its parent context is cancelled.
+WithDeadline and variants such as WithCancelCause must be called,
+or the new context will remain live until its parent context is cancelled.
 (The background context is never cancelled.)
 
 Default: on.

gopls/internal/doc/api.json

@@ -466,7 +466,7 @@
 						},
 						{
 							"Name": "\"lostcancel\"",
-							"Doc": "check cancel func returned by context.WithCancel is called\n\nThe cancellation function returned by context.WithCancel, WithTimeout,\nand WithDeadline must be called or the new context will remain live\nuntil its parent context is cancelled.\n(The background context is never cancelled.)",
+							"Doc": "check cancel func returned by context.WithCancel is called\n\nThe cancellation function returned by context.WithCancel, WithTimeout,\nWithDeadline and variants such as WithCancelCause must be called,\nor the new context will remain live until its parent context is cancelled.\n(The background context is never cancelled.)",
 							"Default": "true"
 						},
 						{
@@ -1114,7 +1114,7 @@
 		},
 		{
 			"Name": "lostcancel",
-			"Doc": "check cancel func returned by context.WithCancel is called\n\nThe cancellation function returned by context.WithCancel, WithTimeout,\nand WithDeadline must be called or the new context will remain live\nuntil its parent context is cancelled.\n(The background context is never cancelled.)",
+			"Doc": "check cancel func returned by context.WithCancel is called\n\nThe cancellation function returned by context.WithCancel, WithTimeout,\nWithDeadline and variants such as WithCancelCause must be called,\nor the new context will remain live until its parent context is cancelled.\n(The background context is never cancelled.)",
 			"URL": "https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/lostcancel",
 			"Default": true
 		},