[
https://issues.apache.org/jira/browse/FREEMARKER-107?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16952255#comment-16952255
]
Dániel Dékány commented on FREEMARKER-107:
------------------------------------------
As I imagine it, {{.args}} will only contain the arguments that were actually
passed to the macro (i.e., you can tell exactly what its content will be, just
by looking at the calling side). Because {{.args}} is for delegating a call to
another macro as is (except that with {{?spreadArgs}} you can do argument value
overrides too). Thus, by {{<@m3?spreadArgs(.args)/>}} you truly "replay" the
original invocation of the containing macro (of {{m1}} or {{m2}} in your
example). That also means that *parameter defaults*, and catch-all parameters
declared in the originally invoked macro (of {{m1}} or {{m2}} in your example)
has no effect on {{.args}}.
On the other hand, some user might will expect that if you declared a macro
parameter called {{foo}}, then {{foo}} and {{.args.foo}} always give the same.
But they may don't, for several reasons: {{foo}} might was a catch-all argument
(and so it's in "exploded" form in {{.args}}), {{foo}} might have a default
(which is not applied in {{.args}}), and last not least, inside a function
{{.args}} is a sequence (a list), so {{.args.someName}} will never work there.
I'm hoping we are on the same page here, but you might realize something
regarding your use case when you think through these.
> Hash expansion to macro arguments (Python **kwargs style)
> ---------------------------------------------------------
>
> Key: FREEMARKER-107
> URL: https://issues.apache.org/jira/browse/FREEMARKER-107
> Project: Apache Freemarker
> Issue Type: New Feature
> Components: engine
> Affects Versions: 2.3.28
> Reporter: Pascal Proulx
> Priority: Major
>
> Hello,
> We heavily rely on Freemarker macros to build a helper template API, but have
> had to make large workarounds for passing contents of hashes as macro
> arguments, for several years. (In truth I should have made this ticket much
> sooner!)
> It would help greatly simplify our work to have hash expansion to macro
> arguments, like this:
> {code:java}
> <#macro myMacro arg1 arg2 arg3="value3">...</#macro>
> <#assign myHash = {"arg1":"value1", "arg2":"value2"}>
> <@myMacro **myHash/><#-- the hash contents are passed as parameters, instead
> of the hash itself -->
> {code}
> This exists in Python:
> {code:java}
> def test_var_args_call(arg1, arg2, arg3):
> pass
> kwargs = {"arg3": 3, "arg2": "two"}
> test_var_args_call(1, **kwargs)
> {code}
> Essentially the hash contents fill in any arguments not explicitly specified.
> For the case where arguments are specified in addition to the hash, you may
> need to decide on a good syntax, e.g.:
> {code:java}
> <@myMacro arg1="value1" **myHash/>{code}
> This example doesn't have much precedent in freemarker syntax but is fairly
> understandable.
> Although we don't need it nearly as much, the same could be done with lists
> and function arguments:
> {code:java}
> <#function myFunc arg1 arg2>...</#function>
> <#assign myList = ["val1", "val2"]>
> ${myFunc(*myList)}
> <#assign myList = ["val2"]>
> ${myFunc("val1", *myList)}
> {code}
> Again similar to Python:
> {code:java}
> def test_var_args_call(arg1, arg2, arg3):
> pass
> args = ("two", 3)
> test_var_args_call(1, *args)
> {code}
> You might want this for consistency, although in practice the hash expansion
> will be many times more useful to us.
> If there's a lack a manpower I could try to see what I can do digging into
> the source, but wanted to bring this up for discussion first. It doesn't
> appear hard to implement to dump a hash into the macro args map, but there is
> defining the syntax.
> We use Freemarker 2.3.28 at the moment.
> Thank you
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
