CMake builds launch target once per every "${command:cmake.launchTargetXXX}" reference

[dslijepcevic]

Brief Issue Summary

It seems that ${command:cmake.launchTargetDirectory}, ${command:cmake.launchTargetFilename} and ${command:cmake.launchTargetPath} are evaluated more than once when launching a configuration. When cmake.buildBeforeRun is true these commands will ensure that launch target exists before evaluating its properties, but the unfortunate side-effect is that the target will get built once per each command reference. This means that if you reference all 3 of them in a launch configuration in launch.json and then once again within the preLaunchTask in tasks.json, your launch target will get built 6 (six) times! And all 6 times you get full output text as well as extension pop-ups about compiling.

I guess this may have been implemented like this for simplicity, but I would still optimize this down to building the launch target exactly once when cmake.buildBeforeRun is true. I believe it should be possible since CMake Tools is fully in charge of the build process.

[bobbrow]

Yeah, that's pretty bad. It seems that the underlying cause is simply that a function written with the intent to prepare binaries for debug/launch was reused to get the current launch target. If you need a quick fix before we update the extension, you can patch the main.js file under ~/.vscode/extensions/ms-vscode.cmake-tools-1.4.2/dist.

line 42520 would change from chosen = current; to return current;. This will exit the function early and skip configuration/build which is unnecessary for these commands.

[dslijepcevic]

Hmm, with that modification I think it behaves as if cmake.buildBeforeRun is set to false. Oh, and also, I don't see these 3 commands in question documented in a single place anywhere. Even extension's Feature Contributions are showing %% in place of descriptions:

[bobbrow]

Sorry about that. I meant to reply back and say that my suggestion wouldn't work for some cases because this function is called in some other scenarios that I didn't realize. I was working on an alternate fix but got pulled away into a few meetings. You'll want to revert any code changes you made in main.js for now.

[bobbrow]

Regarding documentation, I thought we had documented this, but I'm not finding a specific page for it. I think we should update cmake-settings.md and add all the supported commands. I also see some references in debug-launch.md

The %% showing in the feature contributions is a vscode bug. microsoft/vscode#54111

[dslijepcevic]

Well, we tried, no worries. But while we're at it, I have a suggestion for a new command: ${command:cmake.buildTargetName}. Should not be too hard to implement I think. It would be useful if you want to perform a build using a task (for example, with cmake.buildTask set to true), but you'd still like to use some of CMake Tools's cool features like active build target. Thanks.

[andreeis]

This should be fixed in CMake Tools 1.5.0 which was published today.
Let us know if you encounter any issues with this release.