Added the selective-enforce and tests

comment.go

@@ -40,9 +40,10 @@ func isGeneratedFile(file *ast.File) bool {
 }
 
 const (
-	ignoreComment               = "//exhaustive:ignore"
-	enforceComment              = "//exhaustive:enforce"
-	defaultRequireIgnoreComment = "//exhaustive:default-require-ignore"
+	ignoreComment                = "//exhaustive:ignore"
+	enforceComment               = "//exhaustive:enforce"
+	defaultRequireIgnoreComment  = "//exhaustive:default-require-ignore"
+	defaultRequireEnforceComment = "//exhaustive:default-require-enforce"
 )
 
 func hasCommentPrefix(comments []*ast.CommentGroup, comment string) bool {

exhaustive_test.go

@@ -48,6 +48,7 @@ func TestExhaustive(t *testing.T) {
 
 	// This tests exercises the default-case-required flag and its escape comment
 	runTest(t, "default-signifies-exhaustive/default-required/...", func() { fDefaultCaseRequired = true })
+	runTest(t, "default-signifies-exhaustive/default-not-required/...", func() { fDefaultCaseRequired = false })
 
 	// Tests for -ignore-enum-members and -ignore-enum-types flags.
 	runTest(t, "ignore-pattern/...", func() {

switch.go

@@ -93,6 +93,12 @@ func switchChecker(pass *analysis.Pass, cfg switchConfig, generated boolCache, c
 			// enforce comment.
 			return true, resultNoEnforceComment
 		}
+		requireDefaultCase := cfg.defaultCaseRequired
+		if hasCommentPrefix(switchComments, defaultRequireIgnoreComment) {
+			requireDefaultCase = false
+		} else if hasCommentPrefix(switchComments, defaultRequireEnforceComment) {
+			requireDefaultCase = true
+		}
 
 		if sw.Tag == nil {
 			return true, resultNoSwitchTag // never possible for valid Go program?
@@ -117,16 +123,13 @@ func switchChecker(pass *analysis.Pass, cfg switchConfig, generated boolCache, c
 		}
 
 		defaultCaseExists := analyzeSwitchClauses(sw, pass.TypesInfo, checkl.found)
-		if !defaultCaseExists && cfg.defaultCaseRequired {
-			// Don't enforce this if the user opted-out
-			if !hasCommentPrefix(switchComments, defaultRequireIgnoreComment) {
-				// Even if the switch explicitly enumerates all the
-				// enum values, the user has still required all switches
-				// to have a default case. We check this first to avoid
-				// early-outs
-				pass.Report(makeMissingDefaultDiagnostic(sw, dedupEnumTypes(toEnumTypes(es))))
-				return true, resultMissingDefaultCase
-			}
+		if !defaultCaseExists && requireDefaultCase {
+			// Even if the switch explicitly enumerates all the
+			// enum values, the user has still required all switches
+			// to have a default case. We check this first to avoid
+			// early-outs
+			pass.Report(makeMissingDefaultDiagnostic(sw, dedupEnumTypes(toEnumTypes(es))))
+			return true, resultMissingDefaultCase
 		}
 		if len(checkl.remaining()) == 0 {
 			// All enum members accounted for.

testdata/src/default-signifies-exhaustive/default-not-required/default_not_required.go

@@ -0,0 +1,28 @@
+package present
+
+import "default-signifies-exhaustive"
+
+func _a(t dse.T) {
+	// No diagnostic because default-require is not set.
+	switch t {
+	case dse.A:
+	case dse.B:
+	}
+}
+
+func _b(t dse.T) {
+	//exhaustive:default-require-enforce this is a comment showing that we can turn it on for select switches
+	switch t { // want "^missing default in switch of type dse.T$"
+	case dse.A:
+	case dse.B:
+	}
+}
+
+func _c(t dse.T) {
+	//exhaustive:default-require-enforce this is happy because it has a default
+	switch t {
+	case dse.A:
+	case dse.B:
+	default:
+	}
+}