Pascal Proulx created FREEMARKER-107:
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Summary: 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
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
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