gopls/internal/regtest: simplify OnceMet expressions with an env helper

Simplify env.Await(OnceMet(...)) to env.OnceMet(...). Aside from
avoiding boilerplate, this makes it easier to identify where we're still
using Await.

Updates golang/go#39384

Change-Id: I57a18242ce6b48e371e5ce4876ef01a6774fe15c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/461917
Reviewed-by: Alan Donovan <adonovan@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>

gopls/internal/lsp/regtest/env.go

@@ -302,13 +302,25 @@ func checkExpectations(s State, expectations []Expectation) (Verdict, string) {
 	return finalVerdict, summary.String()
 }
 
+// Await blocks until the given expectations are all simultaneously met.
+//
+// Generally speaking Await should be avoided because it can block indefinitely
+// if gopls ends up in a state where the expectations are never going to be
+// met. Use AfterChange or OnceMet instead, so that the runner knows when to
+// stop waiting.
 func (e *Env) Await(expectations ...Expectation) {
 	e.T.Helper()
 	if err := e.Awaiter.Await(e.Ctx, expectations...); err != nil {
 		e.T.Fatal(err)
 	}
 }
 
+// OnceMet blocks until precondition is met or unmeetable; if the precondition
+// is met, it atomically checks that all expectations in mustMeets are met.
+func (e *Env) OnceMet(precondition Expectation, mustMeets ...Expectation) {
+	e.Await(OnceMet(precondition, mustMeets...))
+}
+
 // Await waits for all expectations to simultaneously be met. It should only be
 // called from the main test goroutine.
 func (a *Awaiter) Await(ctx context.Context, expectations ...Expectation) error {

gopls/internal/lsp/regtest/expectation.go

@@ -291,11 +291,9 @@ func (e *Env) DoneDiagnosingChanges() Expectation {
 // expectations.
 func (e *Env) AfterChange(expectations ...Expectation) {
 	e.T.Helper()
-	e.Await(
-		OnceMet(
-			e.DoneDiagnosingChanges(),
-			expectations...,
-		),
+	e.OnceMet(
+		e.DoneDiagnosingChanges(),
+		expectations...,
 	)
 }
 

gopls/internal/regtest/codelens/codelens_test.go

@@ -208,16 +208,14 @@ require golang.org/x/hello v1.2.3
 				env.OpenFile("b/go.mod")
 				env.ExecuteCodeLensCommand("a/go.mod", command.CheckUpgrades, nil)
 				d := &protocol.PublishDiagnosticsParams{}
-				env.Await(
-					OnceMet(
-						env.DiagnosticAtRegexpWithMessage("a/go.mod", `require`, "can be upgraded"),
-						ReadDiagnostics("a/go.mod", d),
-						// We do not want there to be a diagnostic for b/go.mod,
-						// but there may be some subtlety in timing here, where this
-						// should always succeed, but may not actually test the correct
-						// behavior.
-						NoMatchingDiagnostics(env.AtRegexp("b/go.mod", `require`)),
-					),
+				env.OnceMet(
+					env.DiagnosticAtRegexpWithMessage("a/go.mod", `require`, "can be upgraded"),
+					ReadDiagnostics("a/go.mod", d),
+					// We do not want there to be a diagnostic for b/go.mod,
+					// but there may be some subtlety in timing here, where this
+					// should always succeed, but may not actually test the correct
+					// behavior.
+					NoMatchingDiagnostics(env.AtRegexp("b/go.mod", `require`)),
 				)
 				// Check for upgrades in b/go.mod and then clear them.
 				env.ExecuteCodeLensCommand("b/go.mod", command.CheckUpgrades, nil)

gopls/internal/regtest/codelens/gcdetails_test.go

@@ -45,11 +45,9 @@ func main() {
 		env.OpenFile("main.go")
 		env.ExecuteCodeLensCommand("main.go", command.GCDetails, nil)
 		d := &protocol.PublishDiagnosticsParams{}
-		env.Await(
-			OnceMet(
-				DiagnosticAt("main.go", 5, 13),
-				ReadDiagnostics("main.go", d),
-			),
+		env.OnceMet(
+			DiagnosticAt("main.go", 5, 13),
+			ReadDiagnostics("main.go", d),
 		)
 		// Confirm that the diagnostics come from the gc details code lens.
 		var found bool

gopls/internal/regtest/diagnostics/builtin_test.go

@@ -30,9 +30,6 @@ const (
 		if !strings.HasSuffix(name, "builtin.go") {
 			t.Fatalf("jumped to %q, want builtin.go", name)
 		}
-		env.Await(OnceMet(
-			env.DoneWithOpen(),
-			NoDiagnostics("builtin.go"),
-		))
+		env.AfterChange(NoDiagnostics("builtin.go"))
 	})
 }