option for limiting code line length

[jvoigtlaender]

When something like

maxLineLength: 80

is put into the config, submissions with lines containing more than 80 characters would be rejected with a message complaining about the offending line(s).

[jvoigtlaender]

This check should happen in the syntax phase, before compilation, and should actually turn into a step before Compilation here:

haskell-template-task/src/Haskell/Template/Task.hs

Lines 129 to 131 in d2f18e2

	\# syntaxCutoff - determines the last step in the syntax phase (later steps are considered semantics)
	\# possible values (and also the order of steps):
	\# Compilation, GhcErrors, HlintErrors, TemplateMatch, TestSuite

That is, it should then also become possible to cut off the syntax phase after a first step named something like LineLengthChecking (well, preferably something shorter).

Part of the rationale is that with #41 it will then even become possible to turn also the potentially costly compilation stuff off in settings where that is desirable.

[jvoigtlaender]

Should be prefixed to

haskell-template-task/src/Haskell/Template/Task.hs

Lines 908 to 923 in 1a726f0

	testPhases reject inform template solutionFile modules config exts submission dirname =
	[
	do
	-- Reject if submission does not compile with provided hidden modules,
	-- but without Test module.
	compilation <- liftIO $ runInterpreter (compiler dirname config noTest)
	checkResult reject compilation reject Nothing $ const $ return ()
	-- Reject if submission does not compile with provided hidden modules.
	-- This only runs when allowModifying is set to True in the config
	-- and displays a custom message telling students not to change type signatures.
	when (runIdentity $ allowModifying config) $ do
	compilationWithTests <- liftIO $ runInterpreter $
	compiler dirname config modules
	checkResult reject compilationWithTests signatureError Nothing $ const $ return ()
	,

so that it runs both on the sample solution and on student submissions.

[jvoigtlaender]

On this:

Part of the rationale is that with #41 it will then even become possible to turn also the potentially costly compilation stuff off in settings where that is desirable.

and in particular after #48, when disableSemantics is set to True and syntaxCutoff to (say) CodeWidth, then also much of the other stuff in grade, in particular the file writing, can be skipped. Maybe even for other settings of syntaxCutoff along with disableSemantics = True some more fine-grained optimizations are possible.