Report unsupport tags/filters more nicely

[jvanzyl]

Right now it's really hard to tell during parsing when a tag/filter is not implemented. You just get a NPE:

java.lang.NullPointerException
	at liqp.nodes.TagNode.<init>(TagNode.java:22)
	at liqp.parser.v4.NodeVisitor.visitOther_tag(NodeVisitor.java:104)
	at liqp.parser.v4.NodeVisitor.visitOther_tag(NodeVisitor.java:24)
	at liquid.parser.v4.LiquidParser$Other_tagContext.accept(LiquidParser.java:588)
	at org.antlr.v4.runtime.tree.AbstractParseTreeVisitor.visitChildren(AbstractParseTreeVisitor.java:46)
	at liquid.parser.v4.LiquidParserBaseVisitor.visitTag(LiquidParserBaseVisitor.java:62)
	at liquid.parser.v4.LiquidParser$TagContext.accept(LiquidParser.java:453)
	at org.antlr.v4.runtime.tree.AbstractParseTreeVisitor.visitChildren(AbstractParseTreeVisitor.java:46)
	at liquid.parser.v4.LiquidParserBaseVisitor.visitAtom_tag(LiquidParserBaseVisitor.java:34)

Which is very hard to figure out what is not implemented.

[msangel]

code to reproduce?

[jvanzyl]

I'll make a test that has a template with a tag that has not been implemented and it should yield the error above. In my case it was happening as the template I was using made use of a post_url tag. Then that worked and it failed again on another tag.

Actually it tells you when a filter is missing, but I don't think the same happens with tags.

[jvanzyl]

So at this location:

https://github.com/bkiers/Liqp/blob/master/src/main/java/liqp/parser/v4/NodeVisitor.java#L103

Placing something like this:

   String tagName = ctx.Id().getText();
    if (tags.containsKey(tagName)) {
      throw new RuntimeException("No tag exists: " + tagName);
    }

    return new TagNode(tags.get(tagName), expressions.toArray(new LNode[expressions.size()]));

Helped me report and find the tags that are missing. Maybe this isn't the ideal way to do this but something like this to help users determine if there are tags missing. I'm testing various Jekyll sites and there are a bunch of tags I'll have to implement so some better reporting would be good.

[jvanzyl]

@msangel What's the recommend way to create templates with custom filters and tags?

[msangel]

The examples in readme are good. I can just suggest to use those variants of apply method that also accept TemplateContext. пт, 20 серп. 2021 о 21:23 Jason van Zyl ***@***.***> пише:

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[jvanzyl]

I'll try and see if there is a test for registering a new tag and using it as this seems not to be working for me. I'll make a test quickly.

[msangel]

Thanks for the commit!