If condition not evaluating properly

In Liquid, the if condition is used to evaluate expressions and execute blocks of code based on the result. If an if condition isn’t evaluating as expected, the issue could lie in how the condition is written, how the data is being passed to the condition, or how the logic is structured. Below is a detailed guide to help you resolve issues related to if conditions in Liquid.

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Common Causes of If Condition Evaluation Errors

1. Incorrect Syntax
2. Data Type Mismatch
3. Nil or Empty Values
4. Logical Errors
5. Using == for False Conditions
6. Issues with Liquid Filters
7. Misunderstanding the Truthy/Falsy Values
8. Nested Conditions

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1. Incorrect Syntax

If you don’t use the correct syntax for if conditions in Liquid, it may not evaluate properly.

Incorrect Syntax Example:

{% if product_list %}
  <p>{{ product_list.name }}</p>
{% else %}
  <p>No products found</p>
{% endif %}

Here, if product_list is nil or an empty collection, the condition may not evaluate as expected, or nothing will be rendered.

Fix: Make sure you properly structure your if statement:

{% if product_list != nil and product_list.size > 0 %}
  <p>{{ product_list.first.name }}</p>
{% else %}
  <p>No products available</p>
{% endif %}

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2. Data Type Mismatch

Liquid works with different types of data (strings, numbers, arrays, booleans). Sometimes, you might be trying to evaluate a condition with an incorrect data type.

Incorrect Example:

{% assign number = "10" %}
{% if number > 5 %}
  <p>The number is greater than 5</p>
{% endif %}

In this case, number is a string, so it will not compare correctly with the number 5.

Fix: Make sure to convert the data type when needed:

{% assign number = "10" | plus: 0 %}
{% if number > 5 %}
  <p>The number is greater than 5</p>
{% endif %}

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3. Nil or Empty Values

Liquid considers nil or empty values as falsy, meaning that an if condition with such values won’t evaluate as true.

Example with Nil:

{% assign product_list = nil %}
{% if product_list %}
  <p>{{ product_list.first.name }}</p>
{% else %}
  <p>No products found</p>
{% endif %}

Here, product_list is nil, so the if condition evaluates to false, and the else block will be executed.

Fix: Ensure you’re checking for nil explicitly, if necessary:

{% if product_list != nil and product_list.size > 0 %}
  <p>{{ product_list.first.name }}</p>
{% else %}
  <p>No products available</p>
{% endif %}

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4. Logical Errors

Logical mistakes in how the condition is constructed can cause it to not evaluate properly. For instance, if you are testing multiple conditions, you might mix up the operators.

Incorrect Example:

{% assign is_logged_in = true %}
{% assign has_permission = false %}
{% if is_logged_in and has_permission %}
  <p>Access granted</p>
{% else %}
  <p>Access denied</p>
{% endif %}

In the above example, the condition should return “Access denied” because has_permission is false, but the logic is correct.

Fix: Make sure the logic in the if condition makes sense:

{% if is_logged_in == true and has_permission == true %}
  <p>Access granted</p>
{% else %}
  <p>Access denied</p>
{% endif %}

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5. Using == for False Conditions

In some cases, Liquid will interpret an empty value, such as an empty string or a zero, as false. If you’re testing a condition that you expect to be false, you should use == to compare the value explicitly.

Incorrect Example:

{% assign user_role = "" %}
{% if user_role %}
  <p>User is assigned a role</p>
{% else %}
  <p>No user role assigned</p>
{% endif %}

Here, user_role is an empty string, but it will still evaluate as “true” in the if condition.

Fix: Explicitly check for an empty string or a nil value:

{% if user_role == "" %}
  <p>No user role assigned</p>
{% else %}
  <p>User is assigned a role</p>
{% endif %}

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6. Issues with Liquid Filters

Sometimes, if conditions may not behave as expected due to how filters are used. Filters modify the values you are checking in the condition, which can sometimes lead to unexpected results.

Incorrect Example:

{% assign product_name = "   " %}
{% if product_name %}
  <p>{{ product_name }}</p>
{% else %}
  <p>No product name</p>
{% endif %}

Here, the string contains spaces, which is considered “truthy,” even though it is empty in the sense that it does not contain meaningful content.

Fix: Trim the value before checking it:

{% if product_name | strip != "" %}
  <p>{{ product_name }}</p>
{% else %}
  <p>No product name</p>
{% endif %}

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7. Misunderstanding the Truthy/Falsy Values

Liquid evaluates the following as falsy:

• nil
• false
• Empty arrays ([])
• Empty strings ("")

Any other value is considered truthy. If you’re not accounting for these falsy values, your conditions may not behave as expected.

Example:

{% assign discount = 0 %}
{% if discount %}
  <p>Discount available!</p>
{% else %}
  <p>No discount available</p>
{% endif %}

Here, discount is 0, which is falsy in Liquid, so the else block will be executed.

Fix: Ensure that 0 or other falsy values are explicitly handled as needed:

{% if discount != 0 %}
  <p>Discount available!</p>
{% else %}
  <p>No discount available</p>
{% endif %}

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8. Nested Conditions

When using nested if conditions, you may encounter issues with how the conditions are structured. Incorrect nesting can cause evaluation errors.

Incorrect Example:

{% if product_list %}
  <p>Products available</p>
  {% if product_list.size > 0 %}
    <p>{{ product_list.first.name }}</p>
  {% endif %}
{% endif %}

In this case, the if checking product_list.size > 0 will only execute if product_list is truthy, which might be redundant or unnecessary.

Fix: You can combine conditions or ensure proper nesting:

{% if product_list and product_list.size > 0 %}
  <p>{{ product_list.first.name }}</p>
{% else %}
  <p>No products available</p>
{% endif %}

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Troubleshooting Summary Table

Issue	Cause	Fix
Incorrect Syntax	Missing {% endif %} or improper structure	Properly close the if statement
Data Type Mismatch	Using incompatible data types	Ensure correct type conversion (e.g., `
Nil or Empty Values	Checking for nil or empty values	Use explicit checks for nil or empty (== nil or size > 0)
Logical Errors	Incorrect operators or condition setup	Review logic for clarity and correctness
Using == for False Conditions	Not checking empty or zero properly	Use == "" or == 0 for falsy conditions
Issues with Filters	Filters altering condition result	Use filters (e.g., strip, downcase) carefully
Misunderstanding Truthy/Falsy Values	False or empty values causing issues	Be aware of falsy values (nil, false, empty strings)
Nested Conditions	Improper nesting of conditions	Combine conditions or ensure correct nesting

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Example Code for Evaluating If Conditions Correctly

{% if product_list != nil and product_list.size > 0 %}
  <p>{{ product_list.first.name }}</p>
{% else %}
  <p>No products available</p>
{% endif %}

This ensures proper evaluation of product_list and handles cases where the collection is empty or nil.