- image.py

	- compile_tex -> tex_to_pdf
		- most code moved to...
- ...new module "latex.py"
- gift.py
	- process_latex
		- an exception is raised if a formula cannot be compiled...
- question.py
	- HtmlQuestion
		- process_text
			- ...the exception is caught
- wrap.py
	- new command-line option "no-checks"
- minor improvements
- more documentation

README.md

@@ -105,10 +105,14 @@ Only formulas inside `$`s are processed (no, e.g., `\textit` or `\textbf` inside
 - `\left(` and `\right)`
 - `\left[` and `\right]`
 - `\begin{bmatrix}` and `\end{bmatrix}`
-- symbols `\sim`
+- symbols `\sim`, `\approx`
 
 More things are probably ok, but I have not tried them yet.
 
+### Safety checks
+
+By default, `wrap` checks whether or not the formulas you wrote between `$`'s can actually be compiled. Right now this involves a call to `pdflatex` *for every formula*, meaning that it can significantly slow down the process. It can be disabled by passing ` --no-checks` (or simply `-n`). It is probably a good idea to actually check the formulas every once in a while (e.g., every time you add a new one), though, since *bad* latex formulas will be (silently) imported by Moodle anyway, and not only will they be incorrectly rendered but they may also mess up subsequent content.  
+
 ## Current limitations
 
 - only *numerical* and *multiple-choice* questions are supported (notice that the GIFT format itself doesn't support every type of question available in Moodle)

gift.py

@@ -1,5 +1,18 @@
 import re
 
+import latex
+
+
+class NotCompliantLatexFormula(Exception):
+
+	def __init__(self, formula: str) -> None:
+
+		self.formula = formula
+
+	def __str__(self) -> str:
+
+		return self.formula
+
 
 html = '[html]'
 
@@ -105,14 +118,16 @@ def from_feedback(text: str) -> str:
 	return '#'*4 + text
 
 
-def process_latex(text: str) -> str:
+def process_latex(text: str, check_compliance: bool = True) -> str:
 	"""
 	Adapts every occurrence of $$ to GIFT.
 
 	Parameters
 	----------
 	text : str
 		Input text.
+	check_compliance: bool
+		Whether or not to check if the formula can be compiled.
 
 	Returns
 	-------
@@ -125,6 +140,12 @@ def replacement(m: re.Match) -> str:
 
 		latex_source = m.group(1)
 
+		if check_compliance:
+
+			if not latex.formula_can_be_compiled(latex_source):
+
+				raise NotCompliantLatexFormula(latex_source)
+
 		for to_be_escaped in ['\\', '{', '}', '=']:
 
 			latex_source = latex_source.replace(to_be_escaped, '\\' + to_be_escaped)
@@ -134,7 +155,7 @@ def replacement(m: re.Match) -> str:
 		return r'\\(' + latex_source + r'\\)'
 
 	# it looks for strings between $'s (that do not include $ itself) and wraps them in \( and \)
-	return re.sub('\$([^\$]*)\$', replacement, text)
+	return re.sub(r'\$([^\$]*)\$', replacement, text)
 
 
 def process_url_images(text: str, width: int, height: int) -> str:

image.py

@@ -1,19 +1,21 @@
 import pathlib
 import shutil
 import subprocess
-from typing import Union, Optional
+from typing import Union
 
 import colors
 
+import latex
 
-def compile_tex(source_file: Union[str, pathlib.Path], timeout: int = 10) -> pathlib.Path:
+
+def tex_to_pdf(source_file: Union[str, pathlib.Path], timeout: int = 10) -> pathlib.Path:
 	"""
 	Compiles a TeX file.
 
 	Parameters
 	----------
 	source_file : str or pathlib.Path
-		Tex file.
+		TeX file.
 	timeout: int
 		Seconds that are given to compile the source.
 
@@ -26,27 +28,20 @@ def compile_tex(source_file: Union[str, pathlib.Path], timeout: int = 10) -> pat
 
 	source_file = pathlib.Path(source_file)
 
-	path_to_compiler = shutil.which('pdflatex')
-
-	assert path_to_compiler, 'cannot find pdflatex'
-
-	command = [path_to_compiler, '-halt-on-error', source_file.name]
-	# command = [path_to_compiler, r'-interaction=nonstopmode', source_file.name]
-
 	try:
 
-		run_summary = subprocess.run(command, capture_output=True, cwd=source_file.parent, timeout=timeout)
+		exit_status = latex.compile_tex(source_file, timeout=timeout)
 
 	except subprocess.TimeoutExpired:
 
 		print(
-			f'{colors.error}could not compile {colors.reset}{source_file}'
-			f' in {colors.reset}{timeout}{colors.error} seconds...probably some bug in the code'
+			f'{colors.error}could not compile {colors.reset}{source_file + ".tex"}'
+			f' {colors.error}in {colors.reset}{timeout}{colors.error} seconds'
 		)
 
 		raise SystemExit
 
-	assert run_summary.returncode == 0, f'{colors.error}errors were found while compiling {colors.reset}{source_file}'
+	assert exit_status == 0, f'{colors.error}errors were found while compiling {colors.reset}{source_file}'
 
 	return source_file.with_suffix('.pdf')
 

latex.py

@@ -0,0 +1,83 @@
+import pathlib
+import shutil
+import subprocess
+import string
+from typing import Union, List, Optional
+
+
+def compile_tex(
+		source_file: Union[str, pathlib.Path], timeout: Optional[int], options: List[str] = ['halt-on-error']) -> int:
+	"""
+	Compiles a TeX file.
+
+	Parameters
+	----------
+	source_file : str or pathlib.Path
+		TeX file.
+	timeout: int
+		Seconds that are given to compile the source.
+	options: list of str
+		Options to be passed to `pdflatex`.
+
+	Returns
+	-------
+	out: int
+		The exit status of the call to `pdflatex`.
+
+	"""
+
+	source_file = pathlib.Path(source_file)
+
+	path_to_compiler = shutil.which('pdflatex')
+
+	assert path_to_compiler, 'cannot find pdflatex'
+
+	command = [path_to_compiler] + [f'-{o}' for o in options] + [source_file.name]
+
+	run_summary = subprocess.run(command, capture_output=True, cwd=source_file.parent, timeout=timeout)
+
+	return run_summary.returncode
+
+
+latex_template = string.Template(r'''
+\documentclass{standalone}
+
+\usepackage{amsmath}
+
+\begin{document}
+
+$$
+$formula
+$$
+
+\end{document}
+''')
+
+
+def formula_can_be_compiled(formula: str, auxiliary_file: str = '__latex_check.tex') -> bool:
+	"""
+	Checks whether a latex formula can be compiled with the above template, `latex_template`.
+
+	Parameters
+	----------
+	formula : str
+		Latex formula.
+	auxiliary_file : str
+		(Auxiliary) TeX file that is created to check the formula.
+
+	Returns
+	-------
+	out: bool
+		`True` if the compilation finished with no errors.
+
+	"""
+
+	tex_source_code = latex_template.substitute(formula=formula)
+
+	with open(auxiliary_file, 'w') as f:
+
+		f.write(tex_source_code)
+
+	exit_status = compile_tex(auxiliary_file, timeout=10, options=['halt-on-error', 'draftmode'])
+
+	return exit_status == 0

question.py

@@ -7,14 +7,17 @@
 import gift
 import image
 import remote
+import colors
 
 
 class HtmlQuestion(metaclass=abc.ABCMeta):
 	"""
 	Abstract class implementing an html-based question.
 	"""
 
-	def __init__(self, name: str, statement: str, images_settings: dict, history: dict, feedback: Optional[str] = None):
+	def __init__(
+			self, name: str, statement: str, images_settings: dict, history: dict, check_latex_formulas: bool,
+			feedback: Optional[str] = None):
 		"""
 		Initializer.
 
@@ -42,7 +45,7 @@ def __init__(self, name: str, statement: str, images_settings: dict, history: di
 
 		self.processing_functions = [
 			functools.partial(gift.process_url_images, width=self.images_width, height=self.images_height),
-			gift.process_new_lines, gift.process_latex
+			gift.process_new_lines, functools.partial(gift.process_latex, check_compliance=check_latex_formulas)
 		]
 
 		# this might be tampered with by subclasses/decorator
@@ -66,7 +69,17 @@ def process_text(self, text: str) -> str:
 
 		for function in (self.pre_processing_functions + self.processing_functions):
 
-			text = function(text)
+			try:
+
+				text = function(text)
+
+			except gift.NotCompliantLatexFormula as e:
+
+				print(
+					f'\n{colors.error}cannot compile latex formula\n {colors.extra_info}{e.formula}{colors.reset} in '
+					f'{colors.info}{self.name}')
+
+				raise SystemExit
 
 		return text
 
@@ -116,10 +129,10 @@ class Numerical(HtmlQuestion):
 	"""
 
 	def __init__(
-			self, name: str, statement: str, images_settings: dict, history: dict, solution: dict,
-			feedback: Optional[str] = None):
+			self, name: str, statement: str, images_settings: dict, history: dict, check_latex_formulas: bool,
+			solution: dict, feedback: Optional[str] = None):
 
-		super().__init__(name, statement, images_settings, history, feedback)
+		super().__init__(name, statement, images_settings, history, check_latex_formulas, feedback)
 
 		assert ('value' in solution), '"value" missing in "solution"'
 
@@ -144,10 +157,10 @@ class MultipleChoice(HtmlQuestion):
 	"""
 
 	def __init__(
-			self, name: str, statement: str, images_settings: dict, history: dict, answers: dict,
-			feedback: Optional[str] = None):
+			self, name: str, statement: str, images_settings: dict, history: dict, check_latex_formulas: bool,
+			answers: dict, feedback: Optional[str] = None):
 
-		super().__init__(name, statement, images_settings, history, feedback)
+		super().__init__(name, statement, images_settings, history, check_latex_formulas, feedback)
 
 		self.answers = answers
 
@@ -174,6 +187,9 @@ def answer(self):
 # ========================================== Decorators
 
 class QuestionDecorator:
+	"""
+	Abstract class to implement a question decorator.
+	"""
 
 	def __init__(self, decorated: Union[HtmlQuestion, 'QuestionDecorator']):
 
@@ -199,6 +215,27 @@ def __setattr__(self, key, value):
 	def transform_files(
 			text: str, pattern: str, process_match: Callable[[str], None],
 			replacement: Union[str, Callable[[re.Match], str]]):
+		"""
+		It searches in a text for strings corresponding to files (maybe including a path), replaces them by another
+		string according to some function and, additionally, processes each file according to another function.
+
+		Parameters
+		----------
+		text : str
+			Input text.
+		pattern : str
+			Regular expression including a capturing group that yields the file.
+		process_match : Callable[[str], None]
+			Function that will *process* each file.
+		replacement : str or Callable[[re.Match], str]
+			Regular expression making use of the capturing group or function processing the match delivered by `pattern`
+
+		Returns
+		-------
+		out: str
+			Output text with the replacements performed, after having processed all the files.
+
+		"""
 
 		# all the matching files in the given text
 		files = re.findall(pattern, text)
@@ -214,6 +251,9 @@ def transform_files(
 
 
 class TexToSvg(QuestionDecorator):
+	"""
+	Decorator to converts TeX files into svg files.
+	"""
 
 	def __init__(self, decorated: Union[HtmlQuestion, QuestionDecorator]):
 
@@ -225,7 +265,7 @@ def process_match(f):
 			if f not in self.history['already compiled']:
 
 				# ...it is...
-				image.pdf_to_svg(image.compile_tex(f))
+				image.pdf_to_svg(image.tex_to_pdf(f))
 
 				# ...and a note is made of it
 				self.history['already compiled'].add(f)
@@ -241,6 +281,9 @@ def process_match(f):
 
 
 class SvgToHttp(QuestionDecorator):
+	"""
+	Decorator to transfer svg files to a remote location.
+	"""
 
 	def __init__(
 			self, decorated: Union[HtmlQuestion, QuestionDecorator], connection: remote.Connection,

remote.py

@@ -51,13 +51,15 @@ def __init__(self, host: str, user: str, password: str, public_key: Union[str, p
 
 		except paramiko.ssh_exception.AuthenticationException:
 
-			print(f'provided username ({user}) and/or password are not valid')
+			print(f'{colors.error}provided username {colors.reset}({user}){colors.error} and/or password are not valid')
 
 			raise SystemExit
 
 		except paramiko.ssh_exception.SSHException:
 
-			print(f'the provided public key ({public_key}) is not valid or has not been decrypted')
+			print(
+				f'{colors.error}the provided public key {colors.reset}({public_key}){colors.error}'
+				f' is not valid or has not been decrypted')
 
 			raise SystemExit
 
@@ -112,8 +114,9 @@ class FakeConnection:
 	For offline runs.
 	"""
 
-	def __init__(self) -> None:
+	def __init__(self, host: str) -> None:
 
+		self.host = host
 		self.already_copied = set()
 
 	@staticmethod
@@ -129,7 +132,7 @@ def copy(self, source: Union[str, pathlib.Path], remote_directory: str):
 
 			print(
 				f'{colors.info}you *should* copy {colors.reset}{source}{colors.info} to'
-				f' {colors.reset}{remote_directory}')
+				f' {colors.reset}{remote_directory}{colors.info} in {colors.reset}{self.host}')
 
 			self.already_copied.add(source.as_posix())