Source Link support in Go To Definition

[davidwengier]

Allow Go To Definition to pull sources from Source Link enabled assemblies.

See also #24349

Background:

• Embed document information into the PDB for types that don't otherwise have it
  • Add documents to PDB for types that have no methods with IL #56278

Process:

• Given a symbol, get the metadata token for it
  • Add public API to retrieve metadata token from ISymbol #53486 / Add ISymbol.MetadataToken #55913
• Given a DLL, find the implementation assembly
  • ref assemblies don't have pdbs, so need a "real" one
    • Can tell by an attribute in the DLL
  • Might be in the nuget cache, so can maybe follow nuget naming conventions
    • eg, if something is in ref\* then we might just need to go to ..\lib\*
    • There might be multiple, for different platforms
    • We know the context you navigated from, and should use that knowledge to find the best one to load
      • Ideally a Nuget API exists for this, since they already know all of this
      • If there is one, make sure its async
    • We should list the other contexts in the nav bar
  • Might be in some platform ref assembly somewhere
    • With .net framework, could just hardcode a mapping. we just need the MVID from the implementation dlls
      • When .NET Framework is serviced, the impl assemblies would get a new guid, but ref assemblies wouldn't change
      • Need a database of all these links, from ref to lib, and some way to automate updating it
    • For .NET Core, can probably ask the runtime/SDK to ship a list if they don't already
    • Whats the story if someone is targeting .net core 3.1, but doesn't have it installed locally
    • Provide mapping of reference assemblies to their implementations sdk#12360
• Given the implementation assembly, find the PDB
  • Debugger will provide this service (exposed over service broker) that gives us the PDB given some information we find in the implementation DLL (MVID)
• Given the PDB and metadata token, find the source link URL
  • Samuel worked of going from metadata token to source link url and document etc.
  • Cherry-pick/cleanup Gtd - samuel #54337
• We need to download the source from the URL
  • Debugger will provide this service, taking into account their various caches
• Put the source in a workspace
  • Miscellaneous workspace is fine to start with
  • Long term would like better support for references etc.
  • Possibly fine for everything, but probably need to create a project to put things in
    • New compilations will have embedded options and references, so should be straight forward
      • Dependencies might be already in our solution, otherwise can ask the debugger for them
  • Metadata-as-source has the same issue so might have some ideas, or existing things to look at
    • Nope! It has the same issue: Decompiler does not decode some assemblies... #58192
• We need to call Codex to let them have a go at finding things too.
• PDB could be embedded. Source could be embedded
  • Go To Definition from source information in PDBs #57073
  • Follow ups:
    • [SourceLink] Ensure embedded source is shown with the right encoding #57350
    • [SourceLink] Ensure source file found on disk matches compiled DLL #57351
    • [SourceLink] Output window logging #57352
    • [SourceLink] Metadata As Source service should use solution snapshot instead of Workspace.CurrentSolution #57353
    • [SourceLink] Use PEReader to try to read pdbs #57417
    • Allow returning multiple file results
    • Don't ignore checksum for SourceLink files, do smarter checks: Try with CRLF, then try with LF
    • Add option for "Always check Microsoft and Nuget symbol servers in GTD"
• Support Go To Implementation/Base: Go to Implementation/Base to include external references #58147
• Support Find All References: Find All References to include external references #59568
• Support Go To All
  • Go To support for decompiled types/members #28275
  • Go To All to include external types #58146
• Investigate using Background Work Indicator for GTD/Source Link #59710
• Add option to always use known symbol servers for embedded and Source Link navigation #59712
• Better handle multiple definitions from Source Link in GTD #59713

Also:

• Need an LSP answer to this now, which may or may not be supported by the current implementation
  • [LSP] Go to Definition doesn't support source link (or decompilation) #58702

[terrajobst]

@jmarolf I think you want this to be either Epic or Theme, probably Epic, right?

[davidwengier]

I feel strangely violated

[jmarolf]

Sorry @davidwengier I am labeling things to see what happens on themeof.net. They don't mean anything yet. Just experiementing

[terrajobst]

They don't mean anything yet.

Now I feel strangely violated

[Meligy]

Is this supposed to work even partially with "remoteHub.richNavigation.enabled": true? Spotted it in #24349 (comment) but probably does not work for non remote repos.

[davidwengier]

@Meligy I'm not sure what that setting means, nor where you would set it. In general Go To Def works regardless of what repo code may come from, but the Source Link aspect would not work if there wasn't Source Link information in the PDBs of the referenced DLLs. If you're having issues with things not working, it's probably best to just log an issue and we can investigate.

[Meligy]

Hi @davidwengier. Thanks for the reply and sorry for not providing enough context. I was checking why Omnisharp decompilation support was not showing implementation for BCL methods (for a simply example, Array.Empty<int>()). And my googling led to #24349 (comment). The setting I mentioned my previous reply is what's shown in the VS Code Settings picture in the comment. I wasn't sure if it's related or not, hence the question.

I understand that in Visual Studio (at least for Windows, maybe for Mac but did not check) there are settings to add symbol servers, download symbols from them, and use these for debugging and maybe decompilation. I was hoping there was something similar when consuming Roslyn via VS Code / Omnisharp.

[davidwengier]

Unfortunately the components that enable Roslyn to download PDBs and Source Link files are part of Visual Studio, and don't ship with OmniSharp/the C# extension.

[JoeRobich]

@Meligy The documentation for configuring Symbol and Source Link options for the .NET Core Debugger in the C# extension can be found at https://github.com/OmniSharp/omnisharp-vscode/blob/master/debugger-launchjson.md#symbol-options

[Meligy]

@JoeRobich thanks a lot. I was actually wondering more about decompilation without debugging (think: right click a symbol and choose "Go to Definition/implementation"). But this is also very useful. I wonder if once downloaded, this become available to use even without debugging.

[JoeRobich]

@Meligy If you set omnisharp.enableDecompilationSupport to true and accept the terms, then with a restart you are able to go to decompilation with the C# extension in VS Code. If you had previously rejected the terms, then you can run the "CSharp: Show decompilation terms agreement" command.