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text/template: Functions are evaluated immediately and #16125

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aarondl opened this issue Jun 20, 2016 · 1 comment
Closed

text/template: Functions are evaluated immediately and #16125

aarondl opened this issue Jun 20, 2016 · 1 comment

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@aarondl
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@aarondl aarondl commented Jun 20, 2016

Please answer these questions before submitting your issue. Thanks!

  1. What version of Go are you using (go version)?
    go version 1.6.2 linux/amd64
  2. What operating system and processor architecture are you using (go env)?
    Ubuntu 16.04 Xenial - Linux, amd64
  3. What did you do?
    If possible, provide a recipe for reproducing the error.
    A complete runnable program is good.
    A link on play.golang.org is best.
    https://play.golang.org/p/zbRIyl8apl
  4. What did you expect to see?
    I expected the function toupper to be passed as an argument to map and for the output of the program to be like this one https://play.golang.org/p/S8LsA-o5KX
  5. What did you see instead?
template: :1:10: executing "" at <toupper>: wrong number of args for toupper: want 1 got 0

It seems like toupper is evaluated as soon as it's seen, which breaks because it's meant to be an argument to the map function.

@adg
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@adg adg commented Jun 20, 2016

That's how template functions work. When they appear by name, they are invoked. They can't be passed as values within templates.

You can, however, pass the function as data, as you can see in this edited version of your first example:
https://play.golang.org/p/9BXHAwda14

@adg adg closed this Jun 20, 2016
@golang golang locked and limited conversation to collaborators Jun 20, 2017
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