[clang/Lex/DependencyDirectivesScanner] Ignore import/include directives with missing filenames without failing the scan

[akyrtzi]

Follow-up to 34ab855826b8cb0c3b46c770b83390bd1fe95c64:

• Don't fail the scan with an include with missing filename, it may be inside a skipped preprocessor block. Let the compilation provide any related error.
• Fix an issue where the lexer was skipping through the next directive, after ignoring the include with missing filename.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Argyrios Kyrtzidis (akyrtzi)

Changes

Follow-up to 34ab855826b8cb0c3b46c770b83390bd1fe95c64:

• Don't fail the scan with an include with missing filename, it may be inside a skipped preprocessor block. Let the compilation provide any related error.
• Fix an issue where the lexer was skipping through the next directive, after ignoring the include with missing filename.

---

Full diff: https://github.com/llvm/llvm-project/pull/100126.diff

2 Files Affected:

• (modified) clang/lib/Lex/DependencyDirectivesScanner.cpp (+1-2)
• (modified) clang/unittests/Lex/DependencyDirectivesScannerTest.cpp (+22-6)

diff --git a/clang/lib/Lex/DependencyDirectivesScanner.cpp b/clang/lib/Lex/DependencyDirectivesScanner.cpp
index 31a4c0f52b465..088d1cc96e3a2 100644
--- a/clang/lib/Lex/DependencyDirectivesScanner.cpp
+++ b/clang/lib/Lex/DependencyDirectivesScanner.cpp
@@ -914,8 +914,7 @@ bool Scanner::lexPPLine(const char *&First, const char *const End) {
   case pp_import:
     // Ignore missing filenames in include or import directives.
     if (lexIncludeFilename(First, End).is(tok::eod)) {
-      skipDirective(Id, First, End);
-      return true;
+      return false;
     }
     break;
   default:
diff --git a/clang/unittests/Lex/DependencyDirectivesScannerTest.cpp b/clang/unittests/Lex/DependencyDirectivesScannerTest.cpp
index 513e184be09ec..bdb5e23510118 100644
--- a/clang/unittests/Lex/DependencyDirectivesScannerTest.cpp
+++ b/clang/unittests/Lex/DependencyDirectivesScannerTest.cpp
@@ -653,12 +653,28 @@ TEST(MinimizeSourceToDependencyDirectivesTest, AtImport) {
 TEST(MinimizeSourceToDependencyDirectivesTest, EmptyIncludesAndImports) {
   SmallVector<char, 128> Out;
 
-  ASSERT_TRUE(minimizeSourceToDependencyDirectives("#import\n", Out));
-  ASSERT_TRUE(minimizeSourceToDependencyDirectives("#include\n", Out));
-  ASSERT_TRUE(minimizeSourceToDependencyDirectives("#ifdef A\n"
-                                                   "#import \n"
-                                                   "#endif\n",
-                                                   Out));
+  ASSERT_FALSE(minimizeSourceToDependencyDirectives("#import\n", Out));
+  EXPECT_STREQ("<TokBeforeEOF>\n", Out.data());
+
+  ASSERT_FALSE(minimizeSourceToDependencyDirectives("#include\n", Out));
+  EXPECT_STREQ("<TokBeforeEOF>\n", Out.data());
+
+  ASSERT_FALSE(minimizeSourceToDependencyDirectives("#ifdef A\n"
+                                                    "#import \n"
+                                                    "#endif\n",
+                                                    Out));
+  // The ifdef block is removed because it's "empty".
+  EXPECT_STREQ("<TokBeforeEOF>\n", Out.data());
+
+  ASSERT_FALSE(minimizeSourceToDependencyDirectives("#ifdef A\n"
+                                                    "#import \n"
+                                                    "#define B\n"
+                                                    "#endif\n",
+                                                    Out));
+  EXPECT_STREQ("#ifdef A\n"
+               "#define B\n"
+               "#endif\n",
+               Out.data());
 }
 
 TEST(MinimizeSourceToDependencyDirectivesTest, AtImportFailures) {