Vscode-cpptools: c_cpp_properties.json is now requiring write access

[daltairwalter]

The c_cpp_properties.json now requires write access or it will not parse. I am using the C/C++ extension 0.16.1 and the vscode version:
Version 1.21.1
Commit 79b44aa704ce542d8ca4a3cc44cfca566e7720f1
Date 2018-03-14T14:46:47.128Z
Shell 1.7.9
Renderer 58.0.3029.110
Node 7.9.0
Architecture x64

We use perforce and I had to check the file out before it would read correctly.
Without this file checked out I get the error:
Failed to parse "h:....vscode\c_cpp_properties.json'

This is a new problem as we have been saving this file in perforce for a while.

[bobbrow]

In this latest version, we wanted to show customers which compiler we were using to populate the system include path and defines as well as which c++ standard IntelliSense was using.

We haven't added any new settings to the c_cpp_properties.json schema in a while. But since we are an extension still in preview and are trying to improve the IntelliSense configuration experience, we do attempt to update existing c_cpp_properties.json files from time to time. We should not make it mandatory to write back to the file though. We should be able to get by with doing this in memory and recomputing the changes if you edit the file again.

[sean-mcmanus]

Is checking the file out, letting the extension modify the file, and then checking the changes back in a workaround? We try to add cppStandard and cStandard values, but I don't think we do that repeatedly if they're already there. On Linux/Mac we try to add compilerPath if a default is found.

But we could add code to check if the file isn't writeable too.

[pyrrho]

Having hit a similar issue, I considered checking the automatically generated changes into git, but not knowing how it will interact with different compiler paths across different computers gives me pause. I've had to switch back and forth between my system clang and a locally-built copy of GCC a fair few times now, so I'm not actually sure that workaround will work for me locally, long-term.

Even if it will work, the idea of committing a system-generated, absolute path into a shared configuration file doesn't sit terribly well with me.

[ghost]

I also hit an issue with VS Code repeatedly updating the c_cpp_properties.json file if it didn't contain the cppStandard and cStandard fields.

This kept me from using certain git commands while VS Code was open (because the working tree wasn't clean). If I stashed the changes to this file, VS Code would just add them back.

As a workaround I just ended up committing the changes to the repo, but I feel like VS Code shouldn't modify this file on its own..

[akoeplinger]

I'm hitting this file being modified now as well and while checking in the cppStandard and cStandard fields sounds OK doing the same for compilerPath does not as it can be different on other machines.

@sean-mcmanus is setting "compilerPath": "" a good workaround or does it have unintended implications?

[bobbrow]

Setting the compiler path to "" turns off the system include and preprocessor symbol discovery logic.

However, a feature I am working on may provide the solution. We're going to add VSCode settings for all of the properties of c_cpp_properties.json so that you can set default values for them and not need to set them in c_cpp_properties.json anymore. I'm working on the writeup for this which I will post in #1338 if you would like to review it and provide feedback.

[akoeplinger]

@bobbrow sounds good but I think there needs to be a short-term fix for this is well, e.g. what you mentioned in https://github.com/Microsoft/vscode-cpptools/issues/1790#issuecomment-378670849

[bobbrow]

Absolutely, though I think both of these will come out in the same release (the next one). I'll mark it for the same milestone so I don't lose track of it.

[bobbrow]

A preview of this is available in the insiders build if you would like to try it out and provide feedback.

[akoeplinger]

@bobbrow thanks, I tried this build but it still writes the fields to the config file all the time.

[bobbrow]

Have you disabled write-access to the file? We will still attempt to write to the file, but we shouldn't crash if the write fails.

[akoeplinger]

@bobbrow no I haven't and I don't see why I should. Those fields should only be written if they don't have the default value.

[bobbrow]

Given the number of configuration issues we've serviced, we are attempting to make it clearer to developers how IntelliSense is configured. And if we don't expose the new properties in some way, people are unlikely to find them.

However, I can move this logic into a configuration upgrade block so that we only attempt to add them once.

[akoeplinger]

Since my main problem with writing to the file is that this is checked into git and shared between colleagues (so hardcoding "compilerPath": "/usr/bin/clang" into the file can't be done) I think using ${default} from https://github.com/Microsoft/vscode-cpptools/issues/1338 will solve the issue much better for me.

Though I should note that https://github.com/Microsoft/vscode-cpptools/issues/1338#issuecomment-380868383 mentions:

Is omitting a configuration option the same as specifying it to ${default}?

Yes.

... which doesn't seem to happen for me, if I omit the compilerPath and save the file just gets updated with hardcoded /usr/bin/clang.

[bobbrow]

Yeah, compilerPath, cStandard, and cppStandard all keep coming back, but the other properties do not. If I move the code that adds these into an upgrade block, then it will only happen once and leave you alone if you want to delete it later.

[bobbrow]

This is fixed in 0.17.0.

In addition, compilerPath, cStandard, cppStandard, and intelliSenseMode will only be force-written to c_cpp_properties.json one last time during the config upgrade to version 4. You should be able to permanently delete them after that if you want to use the defaults for your platform or the new default settings we added to the extension.