NotifySubscribe/NotifyUnsubscribe and Update to PEGTL 3.0.0 Release

I bumped the minor version to 3.3.0 to reflect the new NotifySubscribe/NotifyUnsubscribe feature. The update to PEGTL technically breaks backwards compatibility with older compilers/toolchains, so I could also bump it up to 4.0.0, but since it's still source compatible with prior versions I left it as is.

• Support for invoking the default Subscription object resolvers on subscribe/unsubscribe.
  • If there's a default Subscription object passed to the Operations constructor, and you call one of the overloads which takes a std::launch policy, it will resolve the subscription query on subscribe with ResolverContext::NotifySubscribe, and on unsubscribe with ResolverContext::NotifyUnsubscribe.
  • Using the older subscribe/unsubscribe overrides, or leaving the default Subscription argument empty, should behave the same as before, except there's now an additional FieldParams::resolverContext member which you may inspect at runtime.
  • You can still override the Subscription object when calling deliver to separate subscription state management from the delivery of events. If you pass deliver a nullptr, it will still fallback to using the default Subscription object.
• Update the PEGTL submodule to the 3.0.0 release tag which just came out.
  • Remove the boot-filesystem fallback now that PEGTL depends on std::filesystem as well, which bumps the minimum compiler toolchain version up on Linux.
  • Clarify compatibility requirements in the README
• Other
  • Miscellaneous bug fixes.
  • Enable clang-format and use that to re-format almost everything.

Make fragment type conditions handle union membership

This is a bugfix release specifically for #112. Unions still work with inline fragment spreads on the option types, but without this fix it's much harder to encapsulate your union handling in standalone fragment definitions.

Bug fixes and CMake build and versioning improvements

Bugs fixed: #105 and #106

You can now build cppgraphqlgen using the add_subdirectory command in CMake as an alternative to importing it with find_package from an external installation.

The version number of the project was getting out of sync with the release tags in git, so now it keeps track of the project version number in a separate version.txt file. Anytime there's a new release tag with a greater version number, the CMake configuration should bump the version it uses in version.txt up to match. This should make it so clones of the git repo automatically stay up to date with released version numbers, and worst case if I forget to bump version.txt before tagging a release, consumers building from a non-git source archive should be at most 1 version number behind since it will have been last updated when building the prior version.

Update to latest 3.0.0-pre commit from PEGTL

Aside from a couple of bug fixes, the biggest difference in this release is that it picked up and fixed a few breaking changes in PEGTL since the last sub-module update. The 3.0.0 version of PEGTL is in a pre-release state and may still introduce breaking changes.

I'm going to submit a PR to update both packages simultaneously in vcpkg. If you use another package manager which doesn't use the sub-module and you want to update cppgraphqlgen to this release, please check whether there's a matching update for PEGTL to go with it.

Fix VS 2017 compilation plus minor build tweaks

The biggest difference between this release and v3.2.0 is a fix for #97, which was a template compilation break in GraphQLService.h specific to VS 2017. I use VS 2019 on Windows which compiled the previous version just fine, and so do gcc and clang on Linux and Mac.

I also updated the optional PEGTL sub-module to the latest master branch commit, and I re-added a GRAPHQL_BUILD_SCHEMAGEN CMake option to suppress building schemagen. I use that in some of my own build pipelines to build schemagen for the host platform and cross-compile the libraries for other target platforms.

Use explicit DLL exports on Windows

This should be backwards compatible at the source/CMake level with previous 3.x versions, but the change is big enough that I decided to rev the minor version to 3.2.

Previously, if you used BUILD_SHARED_LIBS on Windows (including building with vcpkg by default), it was setting CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS and letting CMake figure out all of the symbols in all of the DLLs and mark them as exported. That bloats the import libs which are used to consume them and increases the binary size considerably.

This release replaces that mechanism with explicit __declspec(dllimport/dllimport) attributes defined conditionally through macros on Windows for the methods which are actually referenced across modules. There should be no duplication of symbols between DLLs, and part of that meant I needed to split graphqlresponse into an independent library target/DLL in order to take a dependency on it from both graphqljson and graphqlservice.

I've tested this with static and shared libraries on Windows and Linux, as well as building with vcpkg and verifying that schemagen and the samples/tests still work.

Doc updates and assorted bug fixes

This is a minor update on top of v3.1.0. The only noticeable change at runtime should be that default arguments of scalar String type should be returned properly from Introspection queries.

This is necessary to get GraphiQL working again, now that we include @deprecated(reason: String = "No longer supported") in the schema. It wanted to parse the string in defaultValue as a GraphQL input type, and not having the quotes embedded in the response broke the parser.

Feature release: Query Validation

This is a comprehensive fix for #69. Per the spec, the service ought to validate every query before execution to make sure the results are not ambiguous.

There may still be runtime field errors that this doesn't catch, and since the last time I looked at that section of the spec there also seems to be a lot more guidance about how to format the errors. I added locations to all of the errors I could, and a path to the runtime field errors.

In the process of building the validation feature with TDD based on the Examples and Counter Examples in the spec, I found a few bugs in SchemaGenerator as well and fixed those. The validation relies on Introspection and helped flush those out.

Validation can be performed separately with Request::validate, or you can use the new Request::resolve overloads which take a peg::ast& query parameter instead of a const peg::ast_node& root parameter, they will make sure the query is validated once before executing it. The old Request::resolve overloads are still there for backwards compatibility, but they have been marked as [[deprecated]]. They will go away the next time there's a major version release.

Fix a few bugs in schemagen and add documentation

If v3.0.3 was working for your GraphQL schema already, this update should not change any runtime behavior. It fixes a couple of bugs in schemagen (#72 and #74), and it adds documentation in the doc sub-directory which among other things clarifies how to handle subscriptions (#67).

Various bug fixes including a crash in schema_exception destructor

Most notably, this release should be better at bubbling up schema_exception and preserving error messages from deeper in the query resolution process.

At least on Windows with VS 2019, the copy constructor hiding that I tried for the fix to #63 broke the contract for std::exception and resulted in a crash when the schema_exception was copied but didn't invoke the default copy of the _errors member. That bug has been in there since v3.0.1.