Feature #15538
Updated by kke (Kimmo Lehto) about 5 years ago
In `Erb`, would it be possible to add a new trim mode that would indent the following content to match the depth of the tag? The tag could for example be `<%|` and it would be enabled using `Erb.new(template, trim_mode: '|')`
## Reason
Something like this would be easy to follow:
``` ruby
1
<%- [2, 3, 4].each do |num| -%>
<%- unless num == 3 -%>
<%= num %>
<%- end -%>
<%- end -%>
5
```
But unfortunately it will render with "extra" indentation:
```
1
2
4
5
```
Currently, to avoid this, you have to write your template using either no indentation:
```
1
<%- [2, 3, 4].each do |num| -%>
<%- unless num == 3 -%>
<%= num %>
<%- end -%>
<%- end -%>
5
```
Or a weird jumpy indentation:
```
1
<%- [2, 3, 4].each do |num| -%>
<%- unless num == 3 -%>
<%= num %>
<%- end -%>
<%- end -%>
5
```
With the `|` trim mode it could be written as:
```ruby
1
<%|- [2, 3, 4].each do |num| -%>
<%- unless num == 3 -%>
<%= num %>
<%- end -%>
<%|- end -%>
5
```
And it would output as desired without the "extra" indentation:
```
1
2
4
5
```
## Using with `=`
It would also be handy if the `|` could be used with `<%=`, perhaps `<%|=`, this would be excellent for example when templating YAML's:
```yaml
<%- bar_content = "- abc\n- " -def" -%>
foo:
bar:
<%|= bar_content |%>
```
Which would produce something like:
```yaml
foo:
bar:
- abc
- def
```
This would require these new tags:
1. `<%|` begin a capturing a block which will be reindented to the column Instead of the `<` character invalid YAML:
```yaml
2. `|%>` end the capturing block foo:
bar:
- abc
3. `<%|=` like regular `<%=` but multiline strings will be reindented - def
```
Currently there's no way to accomplish this without manually counting the column of the `<` character
Optionally versions of the block tags with whitespace trim control:
4. `<%-|` like `<%|` but if block outputs nothing, remove leading whitespace
5. `|-%>`like `|%>` but remove trailing whitespace spaces and linefeed from the line this tag appears on using something like:
```yaml
<%- bar_content = "- abc\n- " -def" -%>
foo:
bar:
<%= bar_content.gsub(/(?<!\A)^(?!$)/m, ' ' * 4) %>
```