Flask-admin: search_placeholder fails with TypeError when using lazy_gettext for column_labels

[fwiersENO]

For translations I use lazy_gettext in column_labels in a ModelView. With version 1.5.3 this results in an error (was working for version 1.5.2):

TypeError: sequence item 0: expected str instance, _LazyString found
at: libsite-packages\flask_admin\contrib\sqla\view.py", line 608, in search_placeholder
at: return 'Search: %s' % u', '.join(placeholders)

Maybe I am doing translations for column-names wrong and there is another (better) way to provide translations for column-names?

I monkey-patched the method locally to use the the previous statements (i.e. just return gettext('Search')) after I also tried to overwrite the method (which worked but the result is not to my liking, see related issue https://github.com/flask-admin/flask-admin/pull/1728 ):

def search_placeholder(self):
    """
    Bug in version 1.5.3: the join on placeholders fails with _LazyString
    """
    if not self.column_searchable_list:
        return 'Search'

    placeholders = []

    for searchable in self.column_searchable_list:
        if isinstance(searchable, InstrumentedAttribute):
            placeholders.append(
                str(self.column_labels.get(searchable.key, searchable.key)))
        else:
            placeholders.append(
                str(self.column_labels.get(searchable, searchable)))

    return gettext('Search') + ': %s' % u', '.join(placeholders)

[mrjoes]

I reviewed and merged #1728, see if the latest master fixes the issue for you.

[fwiersENO]

I have not tried the latest master but I do no think it will work since the cause of the exception is not resolved. Below a small test-program I used to reproduce the issue:

from flask_babelex import lazy_gettext

column_searchable_list = ['first_name', 'last_name']
column_labels = {
    'first_name': lazy_gettext('First name'),
    'last_name': lazy_gettext('Last name')
}

placeholders = []
for searchable in column_searchable_list:
    placeholders.append(column_labels.get(searchable, searchable))
try:
    search_placeholder = u', '.join(placeholders)
    print("Yes: " + search_placeholder)
except Exception:
    print("No")

placeholders = []
for searchable in column_searchable_list:
    placeholders.append(str(column_labels.get(searchable, searchable)))

try:
    search_placeholder = u', '.join(placeholders)
    print("Yes: " + search_placeholder)
except Exception:
    print("No")

[LionelR]

Last master version installed and this bug is still present.
For some Views, removing the column name in a related parent-child table do the trick

# break in 1.5.3, fine in 1.5.2
column_list = ['parent_table.child_table.name']
column_labels = {'parent_table.child_table.name': lazy_gettext('Name')}

fix:

column_list = ['parent_table.child_table']
column_labels = {'parent_table.child_table': lazy_gettext('Name')}

For others views and as mentioned by @fwiersVANAD, a simple

def search_placeholder(self):
    return gettext('Search')

is a simple and clean solution

[selurvedu]

I can confirm that this bug is not fixed on latest release. I was able to work around it by using hints from previous comments and by looking at the current implementation in flask-admin. Just add this to your ModelView.

    def search_placeholder(self):
        if self.column_searchable_list:
            return ", ".join(
                str(self.column_labels.get(col, col))
                for col in self.column_searchable_list
            )