Add test for missing pch files to document shortcoming

Author: adrian-prantl

lldb/test/API/lang/swift/clangimporter/missing_pch/Foo.swift

@@ -0,0 +1,3 @@
+public func foo(_ x : Int) -> Int {
+  return x + x
+}

lldb/test/API/lang/swift/clangimporter/missing_pch/Makefile

@@ -0,0 +1,25 @@
+SWIFT_SOURCES := main.swift
+SWIFT_OBJC_INTEROP := 1
+SWIFTFLAGS_EXTRAS = -I$(BUILDDIR)
+LD_EXTRAS = -L$(BUILDDIR) -lFoo
+
+all: libFoo.dylib $(EXE)
+
+include Makefile.rules
+
+OVERLAY := $(BUILDDIR)/overlay.yaml
+lib%.dylib: %.swift
+	echo "struct S {};">$(BUILDDIR)/header.h
+	$(MAKE) MAKE_DSYM=$(MAKE_DSYM) CC=$(CC) SWIFTC=$(SWIFTC) \
+		ARCH=$(ARCH) DSYMUTIL=$(DSYMUTIL) \
+		BASENAME=$(shell basename $< .swift) \
+	        SWIFT_BRIDGING_HEADER=header.h \
+		SWIFT_PRECOMPILE_BRIDGING_HEADER=YES \
+                VPATH=$(SRCDIR) -I $(SRCDIR) -f $(SRCDIR)/dylib.mk all
+	rm -f $(OVERLAY)
+
+clean::
+	$(MAKE) MAKE_DSYM=$(MAKE_DSYM) CC=$(CC) SWIFTC=$(SWIFTC) \
+		ARCH=$(ARCH) DSYMUTIL=$(DSYMUTIL) \
+		BASENAME=$(shell basename $< .swift) \
+		VPATH=$(SRCDIR) -I $(SRCDIR) -f $(SRCDIR)/dylib.mk clean

lldb/test/API/lang/swift/clangimporter/missing_pch/TestSwiftMissingPCH.py

@@ -0,0 +1,31 @@
+import lldb
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.decorators import *
+import lldbsuite.test.lldbutil as lldbutil
+import unittest2
+import os
+
+class TestSwiftMissingVFSOverlay(TestBase):
+    mydir = TestBase.compute_mydir(__file__)
+
+    NO_DEBUG_INFO_TESTCASE = True
+
+    def setUp(self):
+        TestBase.setUp(self)
+
+    # Don't run ClangImporter tests if Clangimporter is disabled.
+    @skipIf(setting=("symbols.use-swift-clangimporter", "false"))
+    @skipUnlessDarwin
+    @swiftTest
+    def test(self):
+        """This used to be a test for a diagnostic, however,
+        this is no longer an unrecoverable error"""
+        self.build()
+        os.unlink(self.getBuildArtifact("header.pch"))
+        lldbutil.run_to_source_breakpoint(
+            self, "break here", lldb.SBFileSpec("main.swift"),
+            extra_images=["Foo"]
+        )
+        # FIXME: This crashes the compiler while trying to diagnose the
+        # missing file (because the source location is inside the missing file).
+        #self.expect("expr y", substrs=["1"])

lldb/test/API/lang/swift/clangimporter/missing_pch/dylib.mk

@@ -0,0 +1,5 @@
+DYLIB_ONLY := YES
+DYLIB_NAME := $(BASENAME)
+DYLIB_SWIFT_SOURCES := $(DYLIB_NAME).swift
+
+include Makefile.rules

lldb/test/API/lang/swift/clangimporter/missing_pch/main.swift

@@ -0,0 +1,4 @@
+import Foo
+
+let y = foo(21)
+print(y) // break here