From f6b205dae16392382324fbca676ef6afe3920642 Mon Sep 17 00:00:00 2001
From: Adam Czachorowski <adamcz@google.com>
Date: Tue, 1 Dec 2020 19:04:42 +0100
Subject: [PATCH] [clangd] ExtractFunction: disable on regions that sometimes,
 but not always return.

apply() will fail in those cases, so it's better to detect it in
prepare() already and hide code action from the user.

This was especially annoying on code bases that use a lot of
RETURN_IF_ERROR-like macros.

Differential Revision: https://reviews.llvm.org/D92408
---
 .../clangd/refactor/tweaks/ExtractFunction.cpp     | 27 +++++++++++++++++++++-
 clang-tools-extra/clangd/unittests/TweakTests.cpp  |  6 ++++-
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/clang-tools-extra/clangd/refactor/tweaks/ExtractFunction.cpp b/clang-tools-extra/clangd/refactor/tweaks/ExtractFunction.cpp
index 18fe7bf3916..8eec42876d6 100644
--- a/clang-tools-extra/clangd/refactor/tweaks/ExtractFunction.cpp
+++ b/clang-tools-extra/clangd/refactor/tweaks/ExtractFunction.cpp
@@ -708,6 +708,27 @@ tooling::Replacement createFunctionDefinition(const NewFunction &ExtractedFunc,
   return tooling::Replacement(SM, ExtractedFunc.InsertionPoint, 0, FunctionDef);
 }
 
+// Returns true if ExtZone contains any ReturnStmts.
+bool hasReturnStmt(const ExtractionZone &ExtZone) {
+  class ReturnStmtVisitor
+      : public clang::RecursiveASTVisitor<ReturnStmtVisitor> {
+  public:
+    bool VisitReturnStmt(ReturnStmt *Return) {
+      Found = true;
+      return false; // We found the answer, abort the scan.
+    }
+    bool Found = false;
+  };
+
+  ReturnStmtVisitor V;
+  for (const Stmt *RootStmt : ExtZone.RootStmts) {
+    V.TraverseStmt(const_cast<Stmt *>(RootStmt));
+    if (V.Found)
+      break;
+  }
+  return V.Found;
+}
+
 bool ExtractFunction::prepare(const Selection &Inputs) {
   const LangOptions &LangOpts = Inputs.AST->getLangOpts();
   if (!LangOpts.CPlusPlus)
@@ -715,8 +736,12 @@ bool ExtractFunction::prepare(const Selection &Inputs) {
   const Node *CommonAnc = Inputs.ASTSelection.commonAncestor();
   const SourceManager &SM = Inputs.AST->getSourceManager();
   auto MaybeExtZone = findExtractionZone(CommonAnc, SM, LangOpts);
+  if (!MaybeExtZone ||
+      (hasReturnStmt(*MaybeExtZone) && !alwaysReturns(*MaybeExtZone)))
+    return false;
+
   // FIXME: Get rid of this check once we support hoisting.
-  if (!MaybeExtZone || MaybeExtZone->requiresHoisting(SM))
+  if (MaybeExtZone->requiresHoisting(SM))
     return false;
 
   ExtZone = std::move(*MaybeExtZone);
diff --git a/clang-tools-extra/clangd/unittests/TweakTests.cpp b/clang-tools-extra/clangd/unittests/TweakTests.cpp
index 07f061b3f2e..85edd92d27d 100644
--- a/clang-tools-extra/clangd/unittests/TweakTests.cpp
+++ b/clang-tools-extra/clangd/unittests/TweakTests.cpp
@@ -607,7 +607,11 @@ TEST_F(ExtractFunctionTest, FunctionTest) {
   // Extract certain return
   EXPECT_THAT(apply(" if(true) [[{ return; }]] "), HasSubstr("extracted"));
   // Don't extract uncertain return
-  EXPECT_THAT(apply(" if(true) [[if (false) return;]] "), StartsWith("fail"));
+  EXPECT_THAT(apply(" if(true) [[if (false) return;]] "),
+              StartsWith("unavailable"));
+  EXPECT_THAT(
+      apply("#define RETURN_IF_ERROR(x) if (x) return\nRETU^RN_IF_ERROR(4);"),
+      StartsWith("unavailable"));
 
   FileName = "a.c";
   EXPECT_THAT(apply(" for([[int i = 0;]];);"), HasSubstr("unavailable"));
-- 
2.11.0