Fix resolveTask

[renkun-ken]

What problem did you solve?

Closes #991

[gowerc]

More for my own knowledge sorry but what is vscode.TaskDefinition. I can't seem to find any details about what this interface actually is in the api documentation :(

[ManuelHentschel]

Just my personal opinion/experience: Last time I tried (~1 year ago), the task api was quite confusing to work with and not really flexible. I tried implementing the typical build/test tasks with the possibility to supply optional arguments to e.g. devtools::install(), but this was not supported by the task API. Instead, the extension had to explicitly register all possible combinations of arguments, which is not feasible. Apparently, the idea is to scan a list of tasks specified elsewhere, e.g. package.json, and parse them.

[renkun-ken]

TaskDefinition is basically the schema of tasks user could specify in tasks.json for that particular task type, in our case, R.

Previously, our resolveTask does not really resolve the task.

[renkun-ken]

Currently, there is a problem that #964 uses ShellQuotedString in the arguments supplied to ShellExecution. Then clicking the icon on the right of the task label

will result in an invalid task definition:

{
	"type": "R",
	"command": "Rscript",
	"args": [
		"-e",
		{
			"value": "devtools::install()",
			"quoting": 2
		}
	],
	"problemMatcher": [],
	"label": "R: Install"
}

I'm wondering if it is necessary to use ShellExecution in the first place? If we use ProcessExecution instead, then there seems to be no quoting issue at all, as implemented at renkun-ken@8384f3a.

[renkun-ken]

I tested using ProcessExecution on Windows, Linux and macOS, and the pre-defined tasks work as expected. And user does not need to take care of argument quoting when they write tasks like this:

{
	"version": "2.0.0",
	"tasks": [
		{
			"type": "R",
			"command": "Rscript",
			"args": [
				"-e",
				"readLines('${file}')",
			],
			"cwd": "${workspaceRoot}",
			"env": {
				"ZZZ_TEST": "test1"
			},
			"problemMatcher": [],
			"label": "R: print file"
		}
	]
}

[renkun-ken]

However, in Windows, the file paths are supplied as is. Maybe we could use some form of notation in args so that the file paths could be properly supplied as R string literals.

> Executing task: C:\Program Files\R\R-4.1.2\bin\Rscript.exe -e readLines('c:\Users\ken\Documents\languageserver\.vscode\tasks.json') <

Error: '\U' used without hex digits in character string starting "'$c:\U"
Execution halted
The terminal process "C:\Program Files\R\R-4.1.2\bin\Rscript.exe '-e', 'readLines('c:\Users\ken\Documents\languageserver\.vscode\tasks.json')'" terminated with exit code: 1.

[renkun-ken]

Thanks @gowerc for the nice work done in renkun-ken#3.

[renkun-ken]

Windows user could use raw string (requires R 4.0+) in task code to make use of the path variables:

{
	"version": "2.0.0",
	"tasks": [
		{
			"type": "R",
			"code": [
				"readLines(r'{${file}}')"
			],
			"group": "build",
			"problemMatcher": [],
			"label": "R test"
		}
	]
}

[gowerc]

@renkun-ken

I was wondering if we should document the use of tasks in the readme? Personally I never found the current way vscode exposes them to users to be that intuitive so was thinking we might get more adoption if we had some more docs on it?

[renkun-ken]

Yes, of course. I'll add an entry to Features which points to Tasks in wiki. If you are interested, you could directly edit the wiki page.

[gowerc]

Makes sense to me, will try and add something