Re: [PATCH] Makefile: add support for generating JSON compilation database

From: Jeff King <peff@peff.net>
Date: Sep 1, 2020, 07:38 UTC
Message-ID: <20200901073827.GA3967005@coredump.intra.peff.net>
In-Reply-To: <xmqqsgc3h28s.fsf@gitster.c.googlers.com>

On Sun, Aug 30, 2020 at 09:24:03PM -0700, Junio C Hamano wrote:

Show 19 quoted lines

> "brian m. carlson" <sandals@crustytoothpaste.net> writes:
> 
> > On 2020-08-30 at 19:28:27, Philippe Blain via GitGitGadget wrote:
> >> From: Philippe Blain <levraiphilippeblain@gmail.com>
> >> 
> >> Tools based on LibClang [1] can make use of a 'JSON Compilation
> >> Database' [2] that keeps track of the exact options used to compile a set
> >> of source files.
> >
> > For additional context why this is valuable, clangd, which is a C
> > language server protocol implementation, can use these files to
> > determine the flags needed to compile a file so it can provide proper
> > editor integration.  As a result, editors supporting the language server
> > protocol (such as VS Code, or Vim with a suitable plugin) can provide
> > better searching, integration, and refactoring tools.
> 
> I found that the proposed commit log was very weak to sell the
> change; some of what you gave above should definitely help strenthen
> it.

Likewise. Looking at the output, I'm confused how it would help with things like searching and refactoring. It might be nice to spell it out for those of us exposed to it for the first time (I tried following the links but remained unenlightened).

I'd also be curious to hear what advantages it gives to add a new Makefile knob rather than just letting interested parties add -MJ to their CFLAGS. Is it just a convenience to create the concatenated form? It seems weird that projects would need to do so themselves with sed hackery (i.e., I'd expect whatever consumes this json to be able to handle multiple files).

-Peff