feat: add find_index, has, and reject filters (#799)

* feat: add find_index, has, and reject filters

* Minor tweaks

* Change semantics of jekyllStyle, add more tests

* Some docs improvements

docs/source/_data/sidebar.yml

@@ -51,10 +51,14 @@ filters:
   escape_once: escape_once.html
   find: find.html
   find_exp: find_exp.html
+  find_index: find_index.html
+  find_index_exp: find_index_exp.html
   first: first.html
   floor: floor.html
   group_by: group_by.html
   group_by_exp: group_by_exp.html
+  has: has.html
+  has_exp: has_exp.html
   inspect: inspect.html
   join: join.html
   json: json.html
@@ -72,6 +76,8 @@ filters:
   push: push.html
   prepend: prepend.html
   raw: raw.html
+  reject: reject.html
+  reject_exp: reject_exp.html
   remove: remove.html
   remove_first: remove_first.html
   remove_last: remove_last.html

docs/source/filters/find_index.md

@@ -0,0 +1,25 @@
+---
+title: find_index
+---
+
+{% since %}v10.21.0{% endsince %}
+
+Return the 0-based index of the first object in an array for which the queried attribute has the given value or return `nil` if no item in the array satisfies the given criteria. For the following `members` array:
+
+```javascript
+const members = [
+  { graduation_year: 2013, name: 'Jay' },
+  { graduation_year: 2014, name: 'John' },
+  { graduation_year: 2014, name: 'Jack' }
+]
+```
+
+Input
+```liquid
+{{ members | find_index: "graduation_year", 2014 | json }}
+```
+
+Output
+```text
+1
+```

docs/source/filters/find_index_exp.md

@@ -0,0 +1,25 @@
+---
+title: find_index_exp
+---
+
+{% since %}v10.21.0{% endsince %}
+
+Return the 0-based index of the first object in an array for which the given expression evaluates to true or return `nil` if no item in the array satisfies the evaluated expression.
+
+```javascript
+const members = [
+  { graduation_year: 2013, name: 'Jay' },
+  { graduation_year: 2014, name: 'John' },
+  { graduation_year: 2014, name: 'Jack' }
+]
+```
+
+Input
+```liquid
+{{ members | find_index_exp: "item", "item.graduation_year == 2014" | json }}
+```
+
+Output
+```text
+1
+```

docs/source/filters/has.md

@@ -0,0 +1,25 @@
+---
+title: has
+---
+
+{% since %}v10.21.0{% endsince %}
+
+Return `true` if the array includes an item for which the queried attribute has the given value or return `false` if no item in the array satisfies the given criteria. For the following `members` array:
+
+```javascript
+const members = [
+  { graduation_year: 2013, name: 'Jay' },
+  { graduation_year: 2014, name: 'John' },
+  { graduation_year: 2014, name: 'Jack' }
+]
+```
+
+Input
+```liquid
+{{ members | has: "graduation_year", 2014 | json }}
+```
+
+Output
+```text
+true
+```

docs/source/filters/has_exp.md

@@ -0,0 +1,25 @@
+---
+title: has_exp
+---
+
+{% since %}v10.21.0{% endsince %}
+
+Return `true` if an item exists in an array for which the given expression evaluates to true or return `false` if no item in the array satisfies the evaluated expression.
+
+```javascript
+const members = [
+  { graduation_year: 2013, name: 'Jay' },
+  { graduation_year: 2014, name: 'John' },
+  { graduation_year: 2014, name: 'Jack' }
+]
+```
+
+Input
+```liquid
+{{ members | has_exp: "item", "item.graduation_year == 2014" | json }}
+```
+
+Output
+```text
+true
+```

docs/source/filters/reject.md

@@ -0,0 +1,118 @@
+---
+title: reject
+---
+
+{% since %}v10.21.0{% endsince %}
+
+Creates an array excluding the objects with a given property value, or excluding [truthy][truthy] values by default when a property is not given.
+
+In this example, assume you have a list of products and you want to filter out kitchen products. Using `reject`, you can create an array excluding only the products that have a `"type"` of `"kitchen"`.
+
+Input
+```liquid
+All products:
+{% for product in products %}
+- {{ product.title }}
+{% endfor %}
+
+{% assign non_kitchen_products = products | reject: "type", "kitchen" %}
+
+Kitchen products:
+{% for product in non_kitchen_products %}
+- {{ product.title }}
+{% endfor %}
+```
+
+Output
+```text
+All products:
+- Vacuum
+- Spatula
+- Television
+- Garlic press
+
+Kitchen products:
+- Vacuum
+- Television
+```
+
+Say instead you have a list of products and you want to exclude taxable products. You can `reject` with a property name but no target value to reject all products with a [truthy][truthy] `"taxable"` value.
+
+Input
+```liquid
+All products:
+{% for product in products %}
+- {{ product.title }}
+{% endfor %}
+
+{% assign not_taxed_products = products | reject: "taxable" %}
+
+Available products:
+{% for product in not_taxed_products %}
+- {{ product.title }}
+{% endfor %}
+```
+
+Output
+```text
+All products:
+- Vacuum
+- Spatula
+- Television
+- Garlic press
+
+Available products:
+- Spatula
+- Television
+```
+
+Additionally, `property` can be any valid Liquid variable expression as used in output syntax, except that the scope of this expression is within each item. For the following `products` array:
+
+```javascript
+const products = [
+    { meta: { details: { class: 'A' } }, order: 1 },
+    { meta: { details: { class: 'B' } }, order: 2 },
+    { meta: { details: { class: 'B' } }, order: 3 }
+]
+```
+
+Input
+```liquid
+{% assign selected = products | reject: 'meta.details["class"]', "B" %}
+{% for item in selected -%}
+- {{ item.order }}
+{% endfor %}
+```
+
+Output
+```text
+- 1
+```
+
+## Jekyll style
+
+{% since %}v10.21.0{% endsince %}
+
+For Liquid users migrating from Jekyll, there's a `jekyllWhere` option to mimic the behavior of Jekyll's `where` filter. This option is set to `false` by default. When enabled, if `property` is an array, the target value is matched using `Array.includes` instead of `==`, which is particularly useful for excluding tags.
+
+```javascript
+const pages = [
+    { tags: ["cat", "food"], title: 'Cat Food' },
+    { tags: ["dog", "food"], title: 'Dog Food' },
+]
+```
+
+Input
+```liquid
+{% assign selected = pages | reject: 'tags', "cat" %}
+{% for item in selected -%}
+- {{ item.title }}
+{% endfor %}
+```
+
+Output
+```text
+Dog Food
+```
+
+[truthy]: ../tutorials/truthy-and-falsy.html

docs/source/filters/reject_exp.md

@@ -0,0 +1,37 @@
+---
+title: reject_exp
+---
+
+{% since %}v10.21.0{% endsince %}
+
+Select all the objects in an array where the expression is false. In this example, assume you have a list of products and you want to hide your kitchen products. Using `reject_exp`, you can create an array that omits only the products that have a `"type"` of `"kitchen"`.
+
+Input
+```liquid
+All products:
+{% for product in products %}
+- {{ product.title }}
+{% endfor %}
+
+{% assign non_kitchen_products = products | reject_exp: "item", "item.type == 'kitchen'" %}
+
+Kitchen products:
+{% for product in non_kitchen_products %}
+- {{ product.title }}
+{% endfor %}
+```
+
+Output
+```text
+All products:
+- Vacuum
+- Spatula
+- Television
+- Garlic press
+
+Kitchen products:
+- Vacuum
+- Television
+```
+
+[truthy]: ../tutorials/truthy-and-falsy.html

docs/source/filters/where.md

@@ -37,6 +37,7 @@ Kitchen products:
 ```
 
 Say instead you have a list of products and you only want to show those that are available to buy. You can `where` with a property name but no target value to include all products with a [truthy][truthy] `"available"` value.
+As a special case, the same will happen if the target value is given but evaluates to `undefined`.
 
 Input
 ```liquid
@@ -70,7 +71,6 @@ The `where` filter can also be used to find a single object in an array when com
 Input
 ```liquid
 {% assign new_shirt = products | where: "type", "shirt" | first %}
-
 Featured product: {{ new_shirt.title }}
 ```
 
@@ -105,9 +105,11 @@ Output
 
 ## Jekyll style
 
-{% since %}v10.19.0{% endsince %}
+{% since %}v10.21.0{% endsince %}
 
-For Liquid users migrating from Jekyll, there's a `jekyllWhere` option to mimic the behavior of Jekyll's `where` filter. This option is set to `false` by default. When enabled, if `property` is an array, the target value is matched using `Array.includes` instead of `==`, which is particularly useful for filtering tags.
+For Liquid users migrating from Jekyll, there's a `jekyllWhere` option to mimic the behavior of Jekyll's `where` filter. This option is set to `false` by default. When enabled, if `property` is an array, the target value is matched using `Array.includes` instead of `==`, which is particularly useful for filtering tags. Additionally, a target value of `undefined` is treated normally, entries matched are exactly those which are themselves `undefined`.
+
+This option affects other array selection filters as well, such as `reject` and `find`.
 
 ```javascript
 const pages = [