Add a delegate to errors.d to make error handling configurable

[ManishKhurana11]

This PR adds a delegate to errors.d to make error handling configurable

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[jacob-carlborg]

I've been planning to do something similar. I don't think this is the best approach. I've been discussing this with Walter and he prefers we add a delegate to make the error handling configurable. By default the delegate would do what verrorPrint does today.

[WalterBright]

LSP Diagnostic request

What is that?

[JinShil]

LSP

That appears to be the Language Server Protocol GSoC project: https://forum.dlang.org/post/tatciprksgbbnczqfxbc@forum.dlang.org

[WalterBright]

That appears to be

We shouldn't have to guess.

Besides, @jacob-carlborg is right. Instead of adding more and more data structures and complexity for error reporting in the compiler, just add a sink delegate that the compiler sends the message to, and the recipient then does what it needs.

[jacob-carlborg]

LSP

For reference, LSP (Language Server Protocol) [1] is a client-server protocol for implementing intellisense (code completion, go to definition, and so on). The client would be a text editor or an IDE and the server would be a daemon running in the background containing all the logic for the intellisense. The idea is that one doesn't have to implement the same intellisense logic (for a given language) for all the text editors out there. It's enough to implement once. Same idea as the separation of a compiler frontend and backend.

Manish Khurana is a Google Summer of Code student that is working on an LSP server that is using DMD as a library.

[1] https://langserver.org

[jacob-carlborg]

Please add a new parameter to the initDMD function [1] that sets the diagnostic handler.

[1]

dmd/src/dmd/frontend.d

Lines 105 to 108 in bc6bb99

	void initDMD(
	const string[] versionIdentifiers = [],
	ContractChecks contractChecks = ContractChecks()
	)

[rainers]

I think this is fine, but please add a test similar to the ones in https://github.com/dlang/dmd/blob/master/test/unit

[rainers]

I've pushed some minor changes:

• added bool return value to the diagnostic handler to allow continuing with standard error output
• made the handler variable __gshared as TLS is not used in dmd

If this is merged, the DiagnosticReporter classes could build on it and could be moved from the core compiler to the frontend library as in master...rainers:move_diagreport. @jacob-carlborg would you be ok with this?

[jacob-carlborg]

Yes.

[RazvanN7]

What is the status of this? Should we merge this or do you have an alternate solution @jacob-carlborg ?

[jacob-carlborg]

I don’t have an alternate solution. But the handler should be set to null in deinitializeDMD or somewhere.

[rainers]

But the handler should be set to null in deinitializeDMD or somewhere.

Ok, I added that.

[rainers]

@jacob-carlborg Is your change request resolved?

As I have contributed to this PR I'm biased and hesitate to merge it myself, I'm using it in my own fork for a language server, though, and would like to reduce differences...

[jacob-carlborg]

Is your change request resolved?

Yes.

[rainers]

Thanks!