Capture, log and handle generic exceptions

Handle any and all unforeseen error conditions gracefully by capturing
the exceptions, logging out for debug purposes and providing the user
with a generic error page.

3 files changed, 38 insertions, 0 deletions

diff --git a/qc_app/__init__.py b/qc_app/__init__.py
index 6b760b9..4810d45 100644
--- a/qc_app/__init__.py
+++ b/qc_app/__init__.py
@@ -7,6 +7,7 @@ from flask import Flask
 from .entry import entrybp
 from .parse import parsebp
 from .dbinsert import dbinsertbp
+from .errors import register_error_handlers
 
 def instance_path():
     """Retrieve the `instance_path`. Raise an exception if not defined."""
@@ -29,4 +30,6 @@ def create_app(instance_dir):
     app.register_blueprint(entrybp, url_prefix="/")
     app.register_blueprint(parsebp, url_prefix="/parse")
     app.register_blueprint(dbinsertbp, url_prefix="/dbinsert")
+
+    register_error_handlers(app)
     return app
diff --git a/qc_app/errors.py b/qc_app/errors.py
new file mode 100644
index 0000000..0da6b3c
--- /dev/null
+++ b/qc_app/errors.py
@@ -0,0 +1,14 @@
+"""Application error handling."""
+import logging
+import traceback
+
+from flask import Flask, render_template
+
+def handle_general_exception(exc: Exception):
+    trace = traceback.format_exc()
+    logging.error("Error: Generic unhandled exception!!\n%s", trace)
+    return render_template("unhandled_exception.html", trace=trace)
+
+def register_error_handlers(app: Flask):
+    """Register top-level error/exception handlers."""
+    app.register_error_handler(Exception, handle_general_exception)
diff --git a/qc_app/templates/unhandled_exception.html b/qc_app/templates/unhandled_exception.html
new file mode 100644
index 0000000..6e6a051
--- /dev/null
+++ b/qc_app/templates/unhandled_exception.html
@@ -0,0 +1,21 @@
+{%extends "base.html"%}
+
+{%block title%}System Error{%endblock%}
+
+{%block css%}
+<link rel="stylesheet" href="/static/css/two-column-with-separator.css" />
+{%endblock%}
+
+{%block contents%}
+<p>
+  An error has occured, and your request has been aborted. Please notify the
+  administrator to try and get this sorted.
+</p>
+<p>
+  Provide the following information to help the administrator figure out and fix
+  the issue:<br />
+  <hr /><br />
+  {{trace}}
+  <hr /><br />
+</p>
+{%endblock%}