[AST] Allow limiting the scope of common AST traversals (getParents, RAV).
Summary:
The goal is to allow analyses such as clang-tidy checks to run on a
subset of the AST, e.g. "only on main-file decls" for interactive tools.
Today, these become "problematically global" by running RecursiveASTVisitors
rooted at the TUDecl, or by navigating up via ASTContext::getParent().
The scope is restricted using a set of top-level-decls that RecursiveASTVisitors
should be rooted at. This also applies to the visitor that populates the
parent map, and so the top-level-decls are considered to have no parents.
This patch makes the traversal scope a mutable property of ASTContext.
The more obvious way to do this is to pass the top-level decls to
relevant functions directly, but this has some problems:
- it's error-prone: accidentally mixing restricted and unrestricted
scopes is a performance trap. Interleaving multiple analyses is
common (many clang-tidy checks run matchers or RAVs from matcher callbacks)
- it doesn't map well to the actual use cases, where we really do want
*all* traversals to be restricted.
- it involves a lot of plumbing in parts of the code that don't care
about traversals.
This approach was tried out in D54259 and D54261, I wanted to like it
but it feels pretty awful in practice.
Caveats: to get scope-limiting behavior of RecursiveASTVisitors, callers
have to call the new TraverseAST(Ctx) function instead of TraverseDecl(TU).
I think this is an improvement to the API regardless.
Reviewers: klimek, ioeric
Subscribers: mgorny, cfe-commits
Differential Revision: https://reviews.llvm.org/D54309
llvm-svn: 346847
diff --git a/clang/unittests/AST/ASTContextParentMapTest.cpp b/clang/unittests/AST/ASTContextParentMapTest.cpp
index a391896..f06f32b 100644
--- a/clang/unittests/AST/ASTContextParentMapTest.cpp
+++ b/clang/unittests/AST/ASTContextParentMapTest.cpp
@@ -17,6 +17,9 @@
#include "clang/ASTMatchers/ASTMatchers.h"
#include "clang/Tooling/Tooling.h"
#include "gtest/gtest.h"
+#include "gmock/gmock.h"
+
+using testing::ElementsAre;
namespace clang {
namespace ast_matchers {
@@ -78,5 +81,30 @@
hasAncestor(cxxRecordDecl(unless(isTemplateInstantiation())))))));
}
+TEST(GetParents, RespectsTraversalScope) {
+ auto AST =
+ tooling::buildASTFromCode("struct foo { int bar; };", "foo.cpp",
+ std::make_shared<PCHContainerOperations>());
+ auto &Ctx = AST->getASTContext();
+ auto &TU = *Ctx.getTranslationUnitDecl();
+ auto &Foo = *TU.lookup(&Ctx.Idents.get("foo")).front();
+ auto &Bar = *cast<DeclContext>(Foo).lookup(&Ctx.Idents.get("bar")).front();
+
+ using ast_type_traits::DynTypedNode;
+ // Initially, scope is the whole TU.
+ EXPECT_THAT(Ctx.getParents(Bar), ElementsAre(DynTypedNode::create(Foo)));
+ EXPECT_THAT(Ctx.getParents(Foo), ElementsAre(DynTypedNode::create(TU)));
+
+ // Restrict the scope, now some parents are gone.
+ Ctx.setTraversalScope({&Foo});
+ EXPECT_THAT(Ctx.getParents(Bar), ElementsAre(DynTypedNode::create(Foo)));
+ EXPECT_THAT(Ctx.getParents(Foo), ElementsAre());
+
+ // Reset the scope, we get back the original results.
+ Ctx.setTraversalScope({&TU});
+ EXPECT_THAT(Ctx.getParents(Bar), ElementsAre(DynTypedNode::create(Foo)));
+ EXPECT_THAT(Ctx.getParents(Foo), ElementsAre(DynTypedNode::create(TU)));
+}
+
} // end namespace ast_matchers
} // end namespace clang