Migrate to Liquid's strictest parser

Liquid now ships with a stricter error mode. Previously, Liquid would allow certain code patterns which appear to be well formed, but which the language doesn't yet support. Liquid's parser would accept this code, but evaluate it incorrectly.

To develop the Liquid language so that these types of code patterns can be supported in the future, we’ve updated the parser to be stricter about the code it accepts.

For example, instead of accepting assign x = false or true and evaluating x to be false, the new stricter error mode reports that this code can’t be parsed. This change means that we’ll be able to update Liquid in the future so it can accept assign x = false or true and correctly evaluate the expression to true.

In the following example, the previous parser would suppress the syntax error caused by trying to assign a logical expression to a variable and would never render Important content.

We've put together a list of common errors we've seen across themes and theme app extensions to help the transition:

Anchor to Expected end_of_string but found pipeExpected end_of_string but found pipe

Anchor to Filters in render tagsFilters in render tags

Using filters outside of variable output, assign and the echo tag throws a syntax error:

Fix by pulling the filter outside of the render tag and into its own variable:

Anchor to Expected end_of_string but found comparisonExpected end_of_string but found comparison

Anchor to Conditional expressions in render tagsConditional expressions in render tags

Using conditional expressions as a value for a render argument throws a syntax error:

Fix by wrapping the render tag with the conditional expression:

Anchor to Expected end_of_string but found colonExpected end_of_string but found colon

Anchor to Using ,[object Object], with key value pairsUsing with with key value pairs

You can pass a single object to a snippet using the with parameter but also including a key value pair causes a syntax error:

Fix by removing with:

Another version of this error you might see is raised as [:colon, ":"] is not a valid expression which you'll see if you use a colon immediately after with. Similarly to above, fix by removing with::

If you want to keep the behavior of with (which in the error example above assigns the value of style to icon, see documentation for more details) then you can specify it like this:

Anchor to Malformed arguments in render tagMalformed arguments in render tag

Missing a value for the responsive attribute:

Fix by adding a value for responsive:

Anchor to Expected end_of_string but found idExpected end_of_string but found id

Anchor to Logical operators in variable assignmentsLogical operators in variable assignments

Logical operators can only be used in if statements. The following throws a syntax error:

Fix by moving the conditional expression into the if statement:

Anchor to Logical operators in case statementsLogical operators in case statements

Just like variables, case statements can't use logical operators:

Depending on the scenario you might need to rework your business logic but the example above could be refactored to be like this:

Anchor to Expected colon but found end_of_stringExpected colon but found end_of_string

Anchor to Malformed arguments passed to render tagMalformed arguments passed to render tag

Fix by adding a value for responsive:

Anchor to Expected colon but found commaExpected colon but found comma

Anchor to Malformed arguments passed to render tagMalformed arguments passed to render tag

Variables passed to a snippet need to be formatted as key value pairs:

Anchor to Unexpected charactersUnexpected characters

This is an all encompassing error that can sometimes be hard to parse where the exact issue is. In most cases the problem is a typo but the line number on the error should help point you to the exact spot. Provided are some common examples we've seen but this isn't an exhaustive list:

Anchor to Conditional expressions using ,[object Object], and ,[object Object], instead of ,[object Object], and ,[object Object]Conditional expressions using && and || instead of and and or

Conditional expressions in Liquid use and and or. Using && and || throws a syntax error:

Fix by using Liquid's boolean operators:

Anchor to Conditional expressions using parenthesesConditional expressions using parentheses

Using parentheses to group conditional expressions throws a syntax error:

Fix by removing the parentheses (and read the documentation on the order in which Liquid parses conditional expressions):

Anchor to Invalid expressions used in case statementInvalid expressions used in case statement

The following results in Liquid syntax error (line 3): Unexpected character =:

To fix this remove the =>:

Anchor to Comments must be written on their own lineComments must be written on their own line

The following results in Liquid syntax error (line 5): Unexpected character #:

To fix this, move the comment to its own line:

Anchor to [object Object], is not a valid expression[:end_of_string] is not a valid expression

Anchor to Malformed arguments passed to render tagMalformed arguments passed to render tag

Fix by adding a value for style::