[Caching] Add swift-scan-test to test libSwiftScan APIs

Add a new test tool, that is a very simple driver to call into
libSwiftScan APIs. This enables testing libSwiftScan interfaces
directly, without relying on cross repo testing from swift-driver.

This allows adding new tests for cache replay feature, that has quite
some unique code path from how replay works in swift-frontend.

Author: cachemeifyoucan

include/swift-c/DependencyScan/DependencyScan.h

@@ -567,7 +567,7 @@ SWIFTSCAN_PUBLIC void swiftscan_cache_query_async(
 SWIFTSCAN_PUBLIC void
     swiftscan_cached_compilation_dispose(swiftscan_cached_compilation_t);
 
-/// Download and materialized the CASObject referenced by the CASID in the local
+/// Download and materialize the CASObject referenced by the CASID in the local
 /// CAS if needed from a remote CAS.
 /// If the return value is SWIFTSCAN_CACHE_RESULT_ERROR, the error message is
 /// returned via \c error parameter and its caller needs to free the message

test/CAS/swift-scan-test.swift

@@ -0,0 +1,24 @@
+// RUN: %empty-directory(%t)
+
+// RUN: %swift-scan-test -action compute_cache_key -cas-path %t/cas -input %s -- %target-swift-frontend -cache-compile-job -Rcache-compile-job %s \
+// RUN:   -emit-module -emit-module-path %t/Test.swiftmodule -c -emit-dependencies -module-name Test -o %t/test.o -cas-path %t/cas \
+// RUN:   -allow-unstable-cache-key-for-testing > %t/key.casid
+
+// RUN: not %swift-scan-test -action cache_query -id @%t/key.casid -cas-path %t/cas 2>&1 | %FileCheck %s --check-prefix=CHECK-QUERY-NOT-FOUND
+
+// RUN: %target-swift-frontend -cache-compile-job -Rcache-compile-job %s -emit-module -emit-module-path %t/Test.swiftmodule -c -emit-dependencies \
+// RUN:  -module-name Test -o %t/test.o -cas-path %t/cas -allow-unstable-cache-key-for-testing
+
+// RUN: %swift-scan-test -action cache_query -id @%t/key.casid -cas-path %t/cas | %FileCheck %s --check-prefix=CHECK-QUERY
+
+// RUN: %swift-scan-test -action replay_result -cas-path %t/cas -id @%t/key.casid -- %target-swift-frontend -cache-compile-job -Rcache-compile-job %s \
+// RUN:   -emit-module -emit-module-path %t/Test2.swiftmodule -c -emit-dependencies -module-name Test -o %t/test2.o -cas-path %t/cas \
+// RUN:   -allow-unstable-cache-key-for-testing
+
+// RUN: diff %t/Test.swiftmodule %t/Test2.swiftmodule
+// RUN: diff %t/test.o %t/test.o
+
+// CHECK-QUERY-NOT-FOUND: cached output not found
+// CHECK-QUERY: Cached Compilation for key "llvmcas://{{.*}}" has 4 outputs: (object) (swiftmodule) (dependencies) (cached-diagnostics)
+
+func testFunc() {}

test/lit.cfg

@@ -345,6 +345,7 @@ config.benchmark_o = inferSwiftBinary('Benchmark_O')
 config.benchmark_driver = inferSwiftBinary('Benchmark_Driver')
 config.wasm_ld = inferSwiftBinary('wasm-ld')
 config.swift_plugin_server = inferSwiftBinary('swift-plugin-server')
+config.swift_scan_test = inferSwiftBinary('swift-scan-test')
 
 config.swift_utils = make_path(config.swift_src_root, 'utils')
 config.line_directive = make_path(config.swift_utils, 'line-directive')
@@ -636,6 +637,7 @@ config.substitutions.append( ('%llvm-strings', config.llvm_strings) )
 config.substitutions.append( ('%target-ptrauth', run_ptrauth ) )
 config.substitutions.append( ('%swift-path', config.swift) )
 config.substitutions.append( ('%swift-plugin-server', config.swift_plugin_server) )
+config.substitutions.append( ('%swift-scan-test', config.swift_scan_test) )
 config.substitutions.append( ('%validate-json', f"{config.python} -m json.tool") )
 
 # This must come after all substitutions containing "%swift".

tools/CMakeLists.txt

@@ -28,6 +28,7 @@ add_swift_tool_subdirectory(libSwiftScan)
 add_swift_tool_subdirectory(libStaticMirror)
 add_swift_tool_subdirectory(libMockPlugin)
 add_swift_tool_subdirectory(swift-plugin-server)
+add_swift_tool_subdirectory(swift-scan-test)
 
 if(SWIFT_INCLUDE_TESTS OR SWIFT_INCLUDE_TEST_BINARIES)
   add_swift_tool_subdirectory(swift-ide-test)

tools/libSwiftScan/CMakeLists.txt

@@ -7,6 +7,7 @@ set(LLVM_EXPORTED_SYMBOL_FILE
 add_swift_host_library(libSwiftScan SHARED
   libSwiftScan.cpp
   c-include-check.c
+  SwiftCaching.cpp
   HAS_SWIFT_MODULES)
 
 if(SWIFT_HOST_VARIANT_SDK IN_LIST SWIFT_DARWIN_PLATFORMS)