Add annotation for read-only properties.

[GoogleCodeExporter]

There is currently no annotation flag that can be used to mark a property (eg. 
a getter) as read-only. The @const annotation flag is not suitable for this 
task because the property value may be variable.

This is a request for a @read-only or @readonly annotation flag.

Original issue reported on code.google.com by RetroModular on 7 Mar 2014 at 10:09

[GoogleCodeExporter]

If you want to make something read-only in code that you're writing, you'd just 
add a getter with no setter. So this is really just for externs. Maybe as an 
alternative, we could just establish a rule that when the compiler sees @const 
in externs, it won't treat it as truly constant (it will assume that the value 
could change over time) but it will still prevent the user from explicitly 
changing the value.

Original comment by tbreisac...@google.com on 7 Mar 2014 at 5:21

[GoogleCodeExporter]

I think the convention Tyler mentioned sounds good. Not a pressing need for yet 
another annotation.

Original comment by dim...@google.com on 7 Mar 2014 at 6:15

[GoogleCodeExporter]

Tyler's suggestion sounds good to me as well. I don't know how the compiler 
treats externs exactly but I guess this new convention wouldn't kill any 
existing optimizations, eg. the inlining of "real" constant values.

Original comment by RetroModular on 7 Mar 2014 at 6:43

[GoogleCodeExporter]

I don't think this is a good idea at all.  @const has a very specific meaning 
and is very important for type checking namespaces and similar.    My thought 
was that properties that were "readonly" would be defined as a getter use 
either ES5 get syntax (externs are always parsed as ES5 or greater now) or 
using Object.defineProperty.

This doesn't require a new annotation is should be clear as to the meaning. 

Original comment by concavel...@gmail.com on 13 Mar 2014 at 12:24

[GoogleCodeExporter]

There currently isn't a way to tell the compiler what is and isn't a getter in 
externs, and there needs to be a way to do that. Consider the following:

    /** @type {number} */
    Foo.prototype.counter;

That property isn't a constant because it doesn't have the @const keyword 
attached to it, so is it read-only or read-write? The compiler *will* be able 
to work out the access rules for that property *if* the compiler encounters the 
property definition in source code but the source code won't always be 
available to the compiler, externs for W3C APIs are a very good example and 
they are what sparked my request for a @readonly annotation to be added.

Original comment by RetroModular on 13 Mar 2014 at 1:34

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Issue tracking has been migrated to github. Please make any further comments on 
this issue through https://github.com/google/closure-compiler/issues

Original comment by blic...@google.com on 1 May 2014 at 6:31

• Added labels: Restrict-AddIssueComment-Nobody

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Original comment by blic...@google.com on 1 May 2014 at 6:34

• Changed state: Duplicate