Re: Proposed: #indent directive

It's easiest to show examples

The not-yet-PR for the maven-dependency-plugin uses these templates:

https://github.com/coyotesong/maven-dependency-plugin/tree/convert-tree-dot-to-velocity/src/main/resources/templates

and more importantly the format-specific content in the 'macros' directory.

It uses the two new Directives I'm proposing. (The other proposal still
needs a lot of work.)

- indent:
https://github.com/coyotesong/maven-dependency-plugin/blob/convert-tree-dot-to-velocity/src/main/java/org/apache/maven/plugins/dependency/utils/velocity/runtime/directive/Indent.java

- collapse:
https://github.com/coyotesong/maven-dependency-plugin/blob/convert-tree-dot-to-velocity/src/main/java/org/apache/maven/plugins/dependency/utils/velocity/runtime/directive/Collapse.java

REAL WORLD EXAMPLES (maven-dependency-plugin PR):

YAML

#macro (showChildDependencies $parent)
#for ($child in $parent.children index $idx)
  #indent
    #showNestingDependencies($child, $idx, $parent.children.size)
  #end
#end
#end

#macro (showNestingDependencies $dependency)
#set ($artifact = $dependency.artifact)
#indent
- groupId: $artifact.groupId
  artifactId: $artifact.artifactId
  version: $artifact.version
  type: $artifact.type
#if ($dependency.hasScope)
  scope: $artifact.scope
#end
#if ($artifact.hasClassifier)
  classifier: $artifact.classifier
#end
  optional: $dependency.optional
#if ($dependency.hasChildren)
  children:
  #showChildDependencies($dependency)
#end
#end
#end


The double indentation isn't required - it's proper YAML if either one is
dropped, but I feel the double indentation is
a little easier to read. Since that's the primary reason I use YAML (vs.
JSON, etc.) that's a big win.

JSON is similar but a bit more gnarly since it requires '[', ']', and
commas on everything but the final item and that
means a lot of extra *#if* directives.


GRAPHML

#**
 * This is expanded for clarity
 *#
#macro (showSimpleDependency $dependency)
#collapse
    <node id="$dependency.id">
      <data key="d0">
        <y:ShapeNode>
          <y:NodeLabel>$dependency.nodeString</y:NodeLabel>
        </y:ShapeNode>
      </data>
    </node>
#end
#end

#**
 * This is expanded for clarity
 *#
#macro (showSimpleEdge $parent $child)
#collapse
    <edge source="$parent.id" target="$child.id">
      <data key="d1">
        <y:PolyLineEdge>
          <y:EdgeLabel>$child.artifact.scope</y:EdgeLabel>
        </y:PolyLineEdge>
      </data>
    </edge>
#end
#end

In this case the format don't *require* what *#collapse* does, but it makes
it much easier for the developer
since they can use the open format shown above yet have it collapsed to a
single line in the final document.
This can substantially reduce the size of the document.

The user can still use the single-line version if they want... but I
suspect most people would prefer the
latter since it makes it easy to have one variable (mostly) per line.

I will probably combine these examples with a POC. JSON doesn't care about
whitespace and it's not
common to have everything but any children on a single line. Proper
indentation is still useful since
it gives the user information about the level of nesting. It will require
tweaking the current *#if directives*
*used to handle the lack of a final comma and the addition of the [ ]
delimiters for the children.*



Bear

On Mon, Apr 7, 2025 at 1:28 AM Claude Brisson <[email protected]>
wrote:

> The use case you give is also not clear to me.
>
> What does `writeNodeAsJson()` do on arrays or maps if you still have to
> call `walktree()` on children? Where is the final ']' or '}' written?
>
> Usually, I do solve such problems of displaying a tree using an extra
> `$indentation` argument which is just passed to the recursive macro with
> additional spaces and it's sufficient (and frankly, this is most easily
> done in Java rather in VTL where it's not exactly pertinent...).
>
>
> On 07/04/2025 00:58, Nathan Bubna wrote:
> > A PR to look over would be good.
> >
> > On Sun, Apr 6, 2025 at 9:41 AM Bear Giles <[email protected]> wrote:
> >
> >> I've been working on a contribution to maven-dependency-plugin and
> spent a
> >> fair amount of time trying to figure out how to cleanly implement proper
> >> indentation when converting the dependency tree to json, yaml, etc.
> >>
> >> After a bit of pain, okay a lot of pain, I have finally implemented a
> new
> >> Directive - 'indent' - which extends Block and prepends a 'padding'
> value
> >> on render(). This works since render() is also called recursively.
> >>
> >> (I know there's a TreeContext but I have no idea how to use it, whether
> it
> >> can be used within the existing plugin, or even if it would help solve
> this
> >> problem.)
> >>
> >> An example of how it is used is:
> >>
> >> #macro (writeNodeAsJson $node)
> >> // do the json magic
> >> #end
> >>
> >> #macro (walktree $node)
> >> #indent
> >>     #writeNodeAsJson($node)
> >>     #foreach ($child in $node.children)
> >>        #walktree ($node)
> >>     #end
> >> #end
> >> #end
> >>
> >> (I don't have that code on this system so there may be a slight error in
> >> it.)
> >>
> >> At the moment the directive doesn't take any parameter but I do plan to
> add
> >> an optional one, ideally either a string literal or a reference, but I
> >> haven't coded it yet. In theory it could even be a reference to a
> different
> >> macro, e.g., so you could have 'I", "II",... then 'a','b'..., then
> >> '1','2'... since the macro could be provided the current indentation
> depth
> >> but I'll leave that for another day.
> >>
> >> I think I have JIRA access and if so I'll create an issue and submit a
> PR.
> >>
> >> Bear Giles
> >>
>
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