Fix memory leak during large csv error handling

- Delay exception raising until context manager `with open()` has finished. - _render_grid now returns a four element tuple (sheets, size, nbr_rows, nbr_cols), where the first two for success and the last two for the `TableTooLargeError`.

Author: cslzchen

mfr/extensions/tabular/render.py

@@ -1,4 +1,5 @@
 import json
+import gc
 import logging
 import os
 
@@ -30,14 +31,23 @@ def render(self):
  )
 
  with open(self.file_path, errors='replace') as fp:
- sheets, size = self._render_grid(fp, self.metadata.ext)
- return self.TEMPLATE.render(
- base=self.assets_url,
- width=settings.TABLE_WIDTH,
- height=settings.TABLE_HEIGHT,
- sheets=json.dumps(sheets),
- options=json.dumps(size),
- )
+ sheets, size, nbr_rows, nbr_cols = self._render_grid(fp, self.metadata.ext)
+ # gc.collect()
+ if sheets and size:
+ return self.TEMPLATE.render(
+ base=self.assets_url,
+ width=settings.TABLE_WIDTH,
+ height=settings.TABLE_HEIGHT,
+ sheets=json.dumps(sheets),
+ options=json.dumps(size),
+ )
+ # gc.collect()
+ raise exceptions.TableTooBigError(
+ 'Table is too large to render.',
+ extension=self.metadata.ext,
+ nbr_cols=nbr_cols,
+ nbr_rows=nbr_rows
+ )
 
  @property
  def file_required(self):
@@ -59,6 +69,11 @@ def _render_grid(self, fp, ext, *args, **kwargs):
  size = settings.SMALL_TABLE
  self._renderer_tabular_metrics['size'] = 'small'
  self._renderer_tabular_metrics['nbr_sheets'] = len(sheets)
+
+ table_too_big = False
+ nbr_cols = 0
+ nbr_rows = 0
+
  for sheet_title in sheets:
  sheet = sheets[sheet_title]
 
@@ -74,10 +89,13 @@ def _render_grid(self, fp, ext, *args, **kwargs):
 
  nbr_rows = len(sheet[1])
  if nbr_cols > settings.MAX_SIZE or nbr_rows > settings.MAX_SIZE:
- raise exceptions.TableTooBigError('Table is too large to render.', extension=ext,
- nbr_cols=nbr_cols, nbr_rows=nbr_rows)
+ table_too_big = True
+ break
+
+ if table_too_big:
+ return None, None, nbr_rows, nbr_cols
 
- return sheets, size
+ return sheets, size, None, None
 
  def _populate_data(self, fp, ext):
  """Determine the appropriate library and use it to populate rows and columns