Separate swift-syntax libs for the compiler and for the library plugins.
Compiler communicates with library plugins using serialized messages
just like executable plugins.
* `lib/swift/host/compiler/lib_Compiler*.dylib`(`lib/CompilerSwiftSyntax`):
swift-syntax libraries for compiler. Library evolution is disabled.
* Compiler (`ASTGen` and `swiftIDEUtilsBridging`) only depends on
`lib/swift/host/compiler` libraries.
* `SwiftInProcPluginServer`: In-process plugin server shared library.
This has one `swift_inproc_plugins_handle_message` entry point that
receives a message and return the response.
* In the compiler
* Add `-in-process-plugin-server-path` front-end option, which specifies
the `SwiftInProcPluginServer` shared library path.
* Remove `LoadedLibraryPlugin`, because all library plugins are managed
by `SwiftInProcPluginServer`
* Introduce abstract `CompilerPlugin` class that has 2 subclasses:
* `LoadedExecutablePlugin` existing class that represents an
executable plugin
* `InProcessPlugins` wraps `dlopen`ed `SwiftInProcPluginServer`
* Unified the code path in `TypeCheckMacros.cpp` and `ASTGen`, the
difference between executable plugins and library plugins are now
abstracted by `CompilerPlugin`
This executable is intended to be installed in the toolchain and act as
an executable compiler plugin just like other 'macro' plugins.
This plugin server has an optional method 'loadPluginLibrary' that
dynamically loads dylib plugins.
The compiler has a newly added option '-external-plugin-path'. This
option receives a pair of the plugin library search path (just like
'-plugin-path') and the corresponding "plugin server" path, separated
by '#'. i.e.
-external-plugin-path
<plugin library search path>#<plugin server executable path>
For exmaple, when there's a macro decl:
@freestanding(expression)
macro stringify<T>(T) -> (T, String) =
#externalMacro(module: "BasicMacro", type: "StringifyMacro")
The compiler look for 'libBasicMacro.dylib' in '-plugin-path' paths,
if not found, it falls back to '-external-plugin-path' and tries to find
'libBasicMacro.dylib' in them. If it's found, the "plugin server" path
is launched just like an executable plugin, then 'loadPluginLibrary'
method is invoked via IPC, which 'dlopen' the library path in the plugin
server. At the actual macro expansion, the mangled name for
'BasicMacro.StringifyMacro' is used to resolve the macro just like
dylib plugins in the compiler.
This is useful for
* Isolating the plugin process, so the plugin crashes doesn't result
the compiler crash
* Being able to use library plugins linked with other `swift-syntax`
versions
rdar://105104850
