group_by_exp fails with object as input

[theonlypwner]

In Jekyll, it is possible to do

{%- assign tags_by_size = site.tags | group_by_exp: 'tag', 'tag[1].size' | sort: 'name' | reverse -%}
{%- for tags_with_size in tags_by_size -%}
{%- for tag in tags_with_size.items -%}
{%- assign tag_name = tag[0] -%}
<!-- ... -->
{{ tag_name }} <sup>{{ tags_with_size.name }}</sup> <!-- tag name and count -->
<!-- ... -->
{%- for post in tag[1] %}
<!-- render each post with this tag -->
<!-- ... -->

However, in liquidjs, collections.postsByTag | group_by_exp: 'tag', 'tag[1].size' (where collections.postsByTag in Eleventy is in the same format as site.tags in Jekyll) just ends up being [ { name: undefined, items: [ [Object] ] } ]

Running collections.postsByTag through Object.entries makes this filter work properly.

This came up while migrating from Jekyll to Eleventy, but I will probably end up reimplementing this functionality, so I might not need it in the end, but I am reporting this missing functionality here.

[harttle]

I guess the issue is about tag[1].size

Do we know the structure of tag here?

[theonlypwner]

site.tags or collections.postsByTag is an object that maps tag names to an array of posts, like {tag0: [post0, post1], tag1: [post1, post2]}, so tag would be an array of size 2, like ["tag0", [post0, post1]]

[harttle]

Please try 10.20.1, let me know if there's still any issue. I created a test case for this issue:

liquidjs/test/e2e/issues.spec.ts

Lines 534 to 560 in 25ef104

	it('group_by_exp fails with object as input #785', () => {
	const site = {
	tags: {
	CPP: [ 'page0' ],
	PHP: [ 'page0', 'page2' ],
	JavaScript: [ 'page1', 'page2', 'page3' ],
	CSharp: [ 'page2', 'page4' ]
	}
	}
	const tpl = `
	{%- assign tags_by_size = site.tags | group_by_exp: 'tag', 'tag[1].size' | sort: 'name' | reverse -%}
	{%- for tags_with_size in tags_by_size -%}
	{%- for tag in tags_with_size.items -%}
	{%- assign tag_name = tag[0] %}
	{{ tag_name }} <sup>{{ tags_with_size.name }}</sup> Posts:
	{%- for post in tag[1] -%}{{post}},{%- endfor -%}
	{%- endfor -%}
	{%- endfor -%}
	`
	const engine = new Liquid()
	const html = engine.parseAndRenderSync(tpl, { site })
	expect(html).toEqual(`
	JavaScript <sup>3</sup> Posts:page1,page2,page3,
	PHP <sup>2</sup> Posts:page0,page2,
	CSharp <sup>2</sup> Posts:page2,page4,
	CPP <sup>1</sup> Posts:page0,`)
	})

[theonlypwner]

It seems to be working in 10.20.1.

In 10.20.0, collections.postsByTag | entries | group_by_exp: 'tag', 'tag[1].size' | ... was the workaround. I had a custom entries filter that calls Object.entries.

In 10.20.1, collections.postsByTag | group_by_exp: 'tag', 'tag[1].size' | ... generates the same output.