Exclude expected completions for underscored attributes

Don't check completions for e.g `@_spi` or its arguments.

Author: hamishknight

SourceKitStressTester/Sources/StressTester/ActionGenerators.swift

@@ -503,6 +503,32 @@ private struct ActionToken {
         return nil
       }
     }
+
+    // Avoid matching for underscored attributes since we hide completions for
+    // those.
+    do {
+      var parent = parent
+      if let label = parent.as(LabeledExprSyntax.self),
+         let labelParent = label.parent, label.label == token {
+        parent = labelParent
+      } else if let nextParent = parent.parent {
+        parent = nextParent
+        if let label = parent.as(LabeledExprSyntax.self),
+           let labelParent = label.parent {
+          parent = labelParent
+        }
+      }
+      if let exprList = parent.as(LabeledExprListSyntax.self),
+         let listParent = exprList.parent {
+        parent = listParent
+      }
+      if let attr = parent.as(AttributeSyntax.self),
+         let ident = attr.attributeName.as(IdentifierTypeSyntax.self),
+         ident.name.text.hasPrefix("_") {
+        return nil
+      }
+    }
+
     if let parent = parent.as(DeclReferenceExprSyntax.self), parent.baseName == token {
       if let refArgs = parent.argumentNames {
         let name = SwiftName(base: token.text, labels: refArgs.arguments.map{ $0.name.text })

SourceKitStressTester/Tests/StressTesterToolTests/ActionGeneratorTests.swift

@@ -97,7 +97,11 @@ class ActionGeneratorTests: XCTestCase {
 
       // FIXME: completion doesn't suggest anonymous closure params (e.g. $0)
       (#line, "$0.first", [/*"$0",*/ "first"]),
-      (#line, "[1,2,4].filter{ $0 == 4 }", ["call:filter"/*, "$0"*/])
+      (#line, "[1,2,4].filter{ $0 == 4 }", ["call:filter"/*, "$0"*/]),
+
+      // We don't include completions for underscored attributes.
+      (#line, "@_underscored(a: Foo)", []),
+      (#line, "@_spi(Foo)", []),
     ]
 
     for test in cases {