Move error handling into separate package.

5 files changed, 131 insertions, 0 deletions

diff --git a/gn_auth/errors/__init__.py b/gn_auth/errors/__init__.py
new file mode 100644
index 0000000..533a842
--- /dev/null
+++ b/gn_auth/errors/__init__.py
@@ -0,0 +1,62 @@
+"""Handle application level errors."""
+import logging
+import traceback
+
+from werkzeug.exceptions import NotFound, HTTPException
+from flask import (Flask,
+                   request,
+                   jsonify,
+                   render_template)
+
+from gn_auth.auth.errors import AuthorisationError
+
+from .tracing import add_trace
+from .http import http_error_handlers
+
+logger = logging.getLogger(__name__)
+
+__all__ = ["register_error_handlers"]
+
+
+def handle_general_exception(exc: Exception):
+    """Handle generic unhandled exceptions."""
+    logger.error("Error occurred!", exc_info=True)
+    content_type = request.content_type
+    if bool(content_type) and content_type.lower() == "application/json":
+        exc_args = [str(x) for x in exc.args]
+        msg = ("The following exception was raised while attempting to access "
+               f"{request.url}: {' '.join(exc_args)}")
+        return jsonify(add_trace(exc, {
+            "error": type(exc).__name__,
+            "error_description": msg
+        })), 500
+
+    return render_template("50x.html",
+                           page=request.url,
+                           error=exc,
+                           trace=traceback.format_exception(exc)), 500
+
+
+def handle_authorisation_error(exc: AuthorisationError):
+    """Handle AuthorisationError if not handled anywhere else."""
+    logger.error("Error occurred!", exc_info=True)
+    logger.error(exc)
+    return jsonify(add_trace(exc, {
+        "error": type(exc).__name__,
+        "error_description": " :: ".join(exc.args)
+    })), exc.error_code
+
+__error_handlers__ = {
+    Exception: handle_general_exception,
+    AuthorisationError: handle_authorisation_error
+}
+
+
+def register_error_handlers(app: Flask):
+    """Register ALL defined error handlers"""
+    _handlers = {
+        **__error_handlers__,
+        **http_error_handlers()
+    }
+    for class_, error_handler in __error_handlers__.items():
+        app.register_error_handler(class_, error_handler)
diff --git a/gn_auth/errors/http/__init__.py b/gn_auth/errors/http/__init__.py
new file mode 100644
index 0000000..f4164d1
--- /dev/null
+++ b/gn_auth/errors/http/__init__.py
@@ -0,0 +1,13 @@
+"""HTTP error handlers."""
+
+from .http_4xx_errors import http_4xx_error_handlers
+from .http_5xx_errors import http_5xx_error_handlers
+
+__all__ = ["http_error_handlers"]
+
+def http_error_handlers() -> dict:
+    """Return *ALL* HTTP error handlers."""
+    return {
+        **http_4xx_error_handlers(),
+        **http_5xx_error_handlers()
+    }
diff --git a/gn_auth/errors/http/http_4xx_errors.py b/gn_auth/errors/http/http_4xx_errors.py
new file mode 100644
index 0000000..704f11b
--- /dev/null
+++ b/gn_auth/errors/http/http_4xx_errors.py
@@ -0,0 +1,31 @@
+"""Handlers for HTTP 4** errors"""
+import logging
+from werkzeug.exceptions import NotFound
+
+from flask import request, jsonify, render_template
+
+from gn_auth.errors.tracing import add_trace
+
+__all__ = ["http_4xx_error_handlers"]
+
+logger = logging.getLogger(__name__)
+
+def page_not_found(exc):
+    """404 handler."""
+    logger.error("Page '%s' was not found.", request.url, exc_info=True)
+    content_type = request.content_type
+    if bool(content_type) and content_type.lower() == "application/json":
+        return jsonify(add_trace(exc, {
+            "error": exc.name,
+            "error_description": (f"The page '{request.url}' does not exist on "
+                                  "this server.")
+        })), exc.code
+
+    return render_template("404.html", page=request.url), exc.code
+
+
+def http_4xx_error_handlers() -> dict:
+    """Return handlers for HTTP errors in the 400-499 range"""
+    return {
+        NotFound: page_not_found
+    }
diff --git a/gn_auth/errors/http/http_5xx_errors.py b/gn_auth/errors/http/http_5xx_errors.py
new file mode 100644
index 0000000..71d09d8
--- /dev/null
+++ b/gn_auth/errors/http/http_5xx_errors.py
@@ -0,0 +1,7 @@
+"""Handlers for HTTP 5** errors."""
+
+__all__ = ["http_5xx_error_handlers"]
+
+def http_5xx_error_handlers() -> dict:
+    """Return handlers for HTTP errors in the 500-599 range"""
+    return {}
diff --git a/gn_auth/errors/tracing.py b/gn_auth/errors/tracing.py
new file mode 100644
index 0000000..25b544f
--- /dev/null
+++ b/gn_auth/errors/tracing.py
@@ -0,0 +1,18 @@
+"""Utilities for improving error tracing."""
+import logging
+import traceback
+
+from flask import request
+
+logger = logging.getLogger(__name__)
+
+
+def add_trace(exc: Exception, errobj: dict) -> dict:
+    """Add the traceback to the error handling object."""
+    logger.error("Endpoint: %s\n%s",
+                 request.url,
+                 traceback.format_exception(exc))
+    return {
+        **errobj,
+        "error-trace": "".join(traceback.format_exception(exc))
+    }