Liquid filters not working as expected

In Power Pages (Power Apps Portals), Liquid filters are used to modify and manipulate data in your templates. When Liquid filters are not behaving as expected, it can cause issues in rendering content or formatting output. This troubleshooting guide will help you identify and resolve issues with Liquid filters not working as intended.

---

What Are Liquid Filters?

Liquid filters are used in Liquid templating language to modify or manipulate output. They are commonly used to:

• Format dates and numbers
• Transform text (e.g., uppercase, lowercase)
• Manipulate arrays and objects
• Perform calculations or transformations on variables

Filters are applied using a pipe (|) after a variable, like so:

liquidCopyEdit{{ user.name | upcase }}

This applies the upcase filter to the user.name variable to convert the text to uppercase.

---

Common Causes of Liquid Filters Not Working

1. Incorrect Filter Syntax
2. Unsupported Filters for the Data Type
3. Filters Applied to Undefined or Nil Variables
4. Incorrect Data Type for the Filter
5. Filter Execution Order Conflicts
6. Caching Issues

---

Example Scenarios and Fixes

1. Incorrect Filter Syntax

Incorrect:

{{ product.price | currency }}

If currency is not a valid filter in your Liquid environment or is misspelled, this can cause the filter to fail.

Fix: Make sure you are using the correct filter for the intended operation. For example, use the money filter in Power Pages (Dataverse):

{{ product.price | money }}

2. Unsupported Filters for Data Type

Incorrect:

{{ user.registration_date | upcase }}

If registration_date is a date object, applying the upcase filter, which is designed for strings, will not work as expected.

Fix: Ensure the correct filter is applied to the correct data type. Use date formatting filters for dates:

{{ user.registration_date | date: "%Y-%m-%d" }}

3. Filters Applied to Undefined or Nil Variables

Incorrect:

{{ user.name | upcase }}

If user is nil (undefined or not assigned), trying to apply a filter will result in an error.

Fix: Check if the variable exists before applying a filter:

{% if user %}
  {{ user.name | upcase }}
{% else %}
  No user name available.
{% endif %}

4. Incorrect Data Type for the Filter

Incorrect:

{{ product.quantity | upcase }}

If quantity is a number, the upcase filter will not work since it’s intended for strings.

Fix: Only apply string filters (like upcase) to text data types. For numbers, use filters like money, round, or format_number:

{{ product.quantity | round }}

---

5. Filter Execution Order Conflicts

Filters may not work as expected if applied in the wrong order.

Incorrect:

{{ "1234" | upcase | reverse }}

This will reverse the string after converting it to uppercase, which might not be the intended behavior.

Fix: Reorder the filters to get the desired result:

{{ "1234" | reverse | upcase }}

---

6. Caching Issues

Sometimes, caching can cause filters to appear as though they are not working correctly. If cached data is returned, you might not see the expected changes immediately after modifying Liquid filters.

Fix: Clear the cache or use cache-busting techniques in Power Pages to force the page to reload with updated data.

{{ "example" | upcase | cache: false }}

Alternatively, manually clear the cache via the Power Pages portal settings.

---

Debugging Liquid Filter Issues

1. Check Filter Syntax

Always double-check the syntax of the filter you are using. The Liquid documentation or Power Pages-specific documentation can be helpful in verifying which filters are supported and how they should be used.

Example of valid filters:

• upcase
• downcase
• date
• money
• json (for formatting JSON data)

2. Inspect Data Types

Ensure you are using the correct filters for the data types you are working with. For instance, text filters should be used for string values, date filters for dates, and number filters for numerical data.

3. Use inspect for Debugging

For debugging purposes, you can output the value of variables before applying filters. This can help identify if the variable contains data and what its type is.

{{ user | inspect }}

4. Use Conditional Checks

Before applying a filter to a variable, check if the variable exists or has a value. This can prevent errors when the variable is nil or empty.

{% if user %}
  {{ user.name | upcase }}
{% else %}
  No user data found.
{% endif %}

5. Test with Sample Data

Test filters with sample data (hardcoded values) to ensure that the filter is working properly:

{{ "hello world" | upcase }}   <!-- Outputs: HELLO WORLD -->
{{ 100 | money }}              <!-- Outputs: $100.00 -->

---

Common Liquid Filters in Power Pages

• upcase / downcase: Converts text to uppercase or lowercase.
• date: Formats dates. {{ user.created_on | date: "%Y-%m-%d" }}
• money: Formats numbers as currency. {{ product.price | money }}
• round: Rounds numbers to a specific number of decimal places.
  {{ 3.14159 | round: 2 }} <!-- Output: 3.14 -->
• default: Provides a fallback value if the variable is nil.
  {{ user.name | default: 'Guest' }}

---

Best Practices for Using Liquid Filters

1. Know the Supported Filters: Always verify which filters are supported in Power Pages (or the specific platform you’re using).
2. Check Data Types: Use filters appropriate for the data type of the object you are manipulating.
3. Conditional Logic: Use {% if %} statements to ensure the variable is not nil before applying filters.
4. Format Dates and Numbers Correctly: Use date and number-specific filters to avoid errors.
5. Test with Sample Data: Always test filters using sample or hardcoded values to ensure they work as expected before applying them to dynamic data.