LC Task Can Fail Without Logging An Error

[benvillalobos]

Issue Description

Someone reported here that the LC task can fail without throwing a warning.

Some times, when I rebuild my solution (C#) in Visual Studio Enterprise 2019, the following error is shown:


Severity	Code	Description	Project	File	Line	Suppression State

Error		The “LC” task returned false but did not log an error.	SBM


Other times, the solution simply builds without a problem.

ToolTaskExtension may be able to return false and not log an error. Note that the LC task does not implement its own execute function.

[Forgind]

I found something very suspicious:

msbuild/src/Utilities/ToolTask.cs

Lines 1439 to 1444 in 4b9f612

	string pathToTool = ComputePathToTool();
	if (pathToTool == null)
	{
	// An appropriate error should have been logged already.
	return false;
	}

attempts to calculate a path to the tool to be executed, and if it's still null after the calculation, it returns false without logging an error, claiming an error already should have been logged.

Looking at that function, if UseCommandProcessor is false, and GenerateFullPathToTool (which is implemented by classes that extend ToolTaskExtension) returns null without logging an error, which sounds legit based on

msbuild/src/Utilities/ToolTask.cs

Lines 500 to 501 in 4b9f612

	// if we cannot find the file, we'll probably error out later on when
	// we try to launch the tool; so do nothing for now

, it will hit this problem.

[Forgind]

I think it will also hit this problem if the tool is cancelled:

msbuild/src/Utilities/ToolTask.cs

Lines 1516 to 1519 in 4b9f612

	if (_terminatedTool)
	{
	return false;
	}

returns false without logging an error if _terminatedTool is true.
That's set to true here.
TerminateToolProcess itself doesn't log an error, so if the tool doesn't log an error before being cancelled, that should lead to ToolTask returning false without logging an error.