evalweb: Improve error handling in compare

evalweb/evalweb.py

@@ -2,8 +2,9 @@ from flask import Blueprint, render_template, request
 from flask_wtf import FlaskForm  # type: ignore
 from wtforms import RadioField   # type: ignore
 from lib.parsing.parser import ParsingError
-from evalweb.web_checker import WebChecker, Language
+from evalweb.web_checker import WebChecker, Language, CompositeException
 from evalweb.examples import examples, convert_examples
+from typing import Optional
 
 
 bp = Blueprint('eval', __name__, url_prefix='/reg')
@@ -64,15 +65,31 @@ def compare() -> str:
         teacher_area = teacher_string
 
         if student_string == "" or teacher_string == "":
-            return render_template('parsing_error.html',
-                                   error="Nebyl zadán vstupní formalismus.")
+            def ifempty(arg: str) -> Optional[str]:
+                if arg == "":
+                    return "Nebyl zadán vstupní formalismus."
+                return None
+
+            return render_template('compare.html',
+                                   error_asgn=ifempty(teacher_string),
+                                   error_sol=ifempty(student_string),
+                                   student_form=student_form,
+                                   teacher_form=teacher_form,
+                                   student_area=student_area,
+                                   teacher_area=teacher_area)
 
         checker = WebChecker(student_string=student_string, task=student_type)
         try:
             result = checker.compare(teacher_string=teacher_string,
                                      teacher_type=teacher_type)
-        except ParsingError as ex:
-            return render_template('parsing_error.html', error=str(ex))
+        except CompositeException as ex:
+            return render_template('compare.html',
+                                   error_asgn=ex.exceptions[0],
+                                   error_sol=ex.exceptions[1],
+                                   student_form=student_form,
+                                   teacher_form=teacher_form,
+                                   student_area=student_area,
+                                   teacher_area=teacher_area)
 
         extra_word_ce, missing_word_ce, inf = None, None, None
         if not result and checker.eq is not None:  # languages not equivalent

evalweb/templates/compare.html

@@ -15,7 +15,13 @@
         <label for="teacher_string">Zadání</label>
         <div>
             <div style="width:400px; float:right;">
-            <textarea style="width:400px;" name="teacher_string" id="teacher_string">{{ teacher_area }}</textarea></div>
+                <textarea style="width:400px;" name="teacher_string" id="teacher_string">{{ teacher_area }}</textarea>
+                {% if error_asgn is defined and error_asgn %}
+                <div class="error">
+                    {{error_asgn}}
+                </div>
+                {% endif %}
+            </div>
             {{ teacher_form.hidden_tag() }}
             <div style="float:left;">{{ teacher_form.make(style="list-style:none") }}</div>
         </div>
@@ -23,7 +29,13 @@
         <label for="student_string">Řešení</label><br>
         <div>
             <div style="width:400px; float:right;">
-                <textarea style="width:400px;" name="student_string" id="student_string">{{ student_area }}</textarea></div>
+                <textarea style="width:400px;" name="student_string" id="student_string">{{ student_area }}</textarea>
+                {% if error_sol is defined and error_sol %}
+                <div class="error">
+                    {{error_sol}}
+                </div>
+                {% endif %}
+            </div>
             {{ student_form.hidden_tag() }}
             <div style="float:left;">{{ student_form.make(style="list-style:none") }}</div>
         </div>

evalweb/templates/parsing_error.html

-{% extends 'base.html' %}
-
-{% block header %}
-    <h1>Výsledek</h1>
-{% endblock %}
-
-{% block content %}
-    <br>Vstupní formalismus nebyl správně zadán, nastala chyba při parsování.<br><br>
-    {{ error }}
-
-{% endblock %}

evalweb/web_checker.py

@@ -51,6 +51,12 @@ class Language:  # contains information about formalism and its language
         return f"{teacher}-{task}:{dfa}"
 
 
+class CompositeException(Exception):
+    def __init__(self, *args: Optional[Exception]) -> None:
+        self.exceptions = args
+        super().__init__()
+
+
 class WebChecker:
     def __init__(self, student_string: str, task: str) -> None:
         self.student_string = student_string
@@ -67,8 +73,18 @@ class WebChecker:
     # nearly equivalent to dfa_task in fja_checker (for IS ROPOTs)
     def dfa_task(self, teacher_type: str, teacher_string: str,
                  task: str, student_string: str) -> bool:
+        error_teach = None
+        try:
             teacher = Language(string=teacher_string, task=teacher_type)
+        except ParsingError as ex:
+            error_teach = ex
+        try:
             student = Language(string=student_string, task=self.task)
+        except ParsingError as ex:
+            raise CompositeException(error_teach, ex)
+        if error_teach:
+            raise CompositeException(error_teach, None)
+
         # only for task checking
         student_solution = transform(student_string, task)