fix(qrgen): fix "trim spaces" checkbox hold state over submits

Only use submitted data to populate form when in POST handler.
Otherwise default value for Boolean field gets clobbered.

app/qrwebform.py

@@ -13,23 +13,20 @@ app.config['SECRET_KEY'] = os.urandom(40)
 
 class QRForm(FlaskForm):
     user_data = TextField("Dane:", validators=[DataRequired()])
-    # setting default here doesn't work, so we cannot retain checkbox state over POST
-    # we force trim_spaced to be checked in the template
-    # see https://github.com/wtforms/flask-wtf/issues/489 https://github.com/wtforms/flask-wtf/issues/362
-    # https://github.com/wtforms/flask-wtf/issues/464
-    trim_spaces = BooleanField("Usuń spacje")
+    trim_spaces = BooleanField("Usuń spacje", default=True)
     submit = SubmitField("Generuj")
 
     @app.route("/", methods=["GET", "POST"])
     def main():
-        form = QRForm(request.form)
 
         if request.method == "POST":
+            form = QRForm(request.form)
             data = request.form["user_data"]
-            if "trim_spaces" in request.form and request.form["trim_spaces"] == "y":
+            if "trim_spaces" in request.form:
                 data = data.replace(" ", "")
         else:
-            # not POST? get back to ourselves
+            # not POST? get back to ourselves, start with empty form
+            form = QRForm()
             data = request.url_root
 
         return render_template("main.html", form=form, data=data, genurl="/render/")

app/templates/main.html

@@ -15,7 +15,7 @@
 
 	<div> {{ form.user_data }} </div>
 	<div class="input submit">
-		{{ form.trim_spaces(checked=True) }} {{ form.trim_spaces.label }}
+		{{ form.trim_spaces }} {{ form.trim_spaces.label }}
 		{{ form.submit }} </div>
 </form>
 </p>