Using filter pipelines

Let’s say we want to modify a colour and then insert its hex into the template:

highlight = {{ (red | sub(saturation=60)).hex }}

$ whiskers -f mocha my-cool-template.txt
Error: Template is invalid

Caused by:
    0: Failed to parse 'test.tera'
    1:  --> 1:42
         |
       1 | highlight = {{ (red | sub(saturation=60)).hex }}
         |                                          ^---
         |
         = expected `or`, `and`, or a variable end (`}}`)

What happened? Well, Tera doesn’t allow inserting parentheses around a filter pipeline like this. Instead, you have to use the get filter:

highlight = {{ (red | sub(saturation=60)).hex }}
highlight = {{ red | sub(saturation=60) | get(key="hex") }}

$ whiskers -f mocha my-cool-template.txt
highlight = cdb1b9

This works for getting any property from an object:

highlight_red = {{ red | sub(saturation=60) | get(key="rgb") | get(key="r") }}

$ whiskers -f mocha my-cool-template.txt
highlight_red = 205

This example is equivalent to adding .rgb.r on the end of the object.

Getting the hex string from a colour at the end of a filter pipeline is such a common need that we added a dedicated hex filter for it:

highlight = {{ red | sub(saturation=60) | get(key="hex") }}
highlight = {{ red | sub(saturation=60) | hex }}

$ whiskers -f mocha my-cool-template.txt
highlight = cdb1b9