Calling a jinja2 filter with only the context as an argument-CodePudding

I'm trying to render a jinja2 template in my service (not using flask, just pure jinja2 and constructing a jinja2 Environment.

Let's say I have the following filter defined

import jinja2

@jinja2.contextfilter
def my_function(context):
    if context.get('my_var'):
        return "hello"
    else:
        return "world"

Super simplified example, but the point of it is that I have some logic that conditionally returns a value based on some variable passed into the context.

Also, I'm using jinja2 2.11 or something like that, which is why I'm using @contextfilter instead of @pass_context.

I've added this filter to my environment using env.filters['my_function'] = my_function

In rendering the template, I'm calling

template = env.get_template('my_template.html')
template.render({'my_var': 'some_value'})

where the template might look something like

... some html here
{{ my_function }}
... some more html

This doesn't actually return "hello", and instead just is empty/blank.

I managed to get it by passing in a dummy variable

@jinja2.contextfilter
def my_function(context, value):
    .... code is the same

And then in the template, I call it with {{ 'hi' | my_function }}. But obviously this is just a hack and not very desirable.

So my question is, how can I call a jinja2 filter function that only takes the context in as an argument? I've tried {{ my_function() }} which returns the error UndefinedError: 'my_function' is undefined, and {{ | my_function }}, which returns the error TemplateSyntaxError: unexpected '|'`

Or is there some other jinja2 construct I should be using?

Edit: my suspicion is that jinja2 uses the | to identify a filter vs a variable, and since I don't have |, then it tries to just render the variable my_function from the context, and since it doesn't exist in the context, it just outputs an empty string.

CodePudding user response：

Jinja2 calls these kind of functions global functions (like range()), not filters. Just change filters to globals in this line:

env.globals['my_function'] = my_function

And then you can call your function in the templates: {{ my_function() }}.