Checking if a chart is closed before rendering html/json (#163)

qf_lib/documents_utils/document_exporting/element/chart.py

@@ -89,6 +89,12 @@ def generate_json(self) -> str:
         -------
         A string with the base64 image (with encoding prefix) of the chart.
         """
+        if self._chart.closed:
+            error_message = 'Chart generation error: The chart you are trying to generate has been already closed. ' \
+                            'Check if you are not trying to regenerate the json for an already processed chart.'
+            self.logger.warning(error_message)
+            return error_message
+
         try:
             result = "data:image/png;base64," + self._chart.render_as_base64_image(
                 self.figsize, self.dpi, self.optimise)
@@ -106,6 +112,13 @@ def generate_html(self, document: Optional[Document] = None) -> str:
         Generates the HTML necessary to display the underlying chart in a PDF document. The chart is rendered in
         memory, then encoded to base64 and embedded in the HTML
         """
+        if self._chart.closed:
+            self.logger.warning('Chart generation error: The chart you are trying to generate has been already closed. '
+                                'Check if you are not trying to regenerate the html for an already processed chart.')
+            result = "<h2 class='chart-render-failure'>Failed to render chart</h1>"
+            result += self._create_html_comment()
+            return result
+
         try:
             base64 = self._chart.render_as_base64_image(self.figsize, self.dpi, self.optimise,
                                                         **self.savefig_settings)
@@ -125,8 +138,7 @@ def generate_html(self, document: Optional[Document] = None) -> str:
 
         except Exception as ex:
             error_message = "{}\n{}".format(ex.__class__.__name__, traceback.format_exc())
-            self.logger.exception('Chart generation error:')
-            self.logger.exception(error_message)
+            self.logger.exception(f'Chart generation error: {error_message}')
             result = "<h2 class='chart-render-failure'>Failed to render chart</h1>"
         # Close the chart's figure as we are no longer going to be using it.
         if self._chart is not None:
@@ -138,7 +150,7 @@ def generate_html(self, document: Optional[Document] = None) -> str:
 
     def _create_html_comment(self):
         template = Template("""
-            <p class="comment">{{ comment }}</p>
-        """)
+                <p class="comment">{{ comment }}</p>
+            """)
 
         return template.render(comment=self.comment)

qf_lib/plotting/charts/chart.py

@@ -95,6 +95,7 @@ def __init__(self, start_x: Any = None, end_x: Any = None, upper_y: Any = None,
         Determines where secondary axes should be created. When Vertical, a vertical axes is created using ``twinx``,
         otherwise a horizontal axes is created using ``twiny``.
         """
+        self.closed = False
 
     @property
     def axes(self):
@@ -179,6 +180,7 @@ def close(self):
         """
         Closes the window containing the figure.
         """
+        self.closed = True
         plt.close(self.figure)
 
     def set_x_range(self, start_x=None, end_x=None):