[OpenAjaxIDE] API metadata: multiple returns

Jon Ferraiolo jferrai at us.ibm.com
Sat Aug 30 00:12:07 PDT 2008

Do we really need to address the general factory case from Gears via
special metadata markup rules, or is it sufficient to ask metadata authors
to explain what's happening within the <description> elements?

If we do feel we need to address this problem, then I would think we need
to come up with a solution that directly addresses the first API that we
encountered (i.e., the Gears factory method) without expecting them to
redesign their API. For their case, I would think you would need markup
that looked something like this:

  <parameter name="classname" .../>
  <returnType datatype="Database" condition="parameter(classname)=
  <returnType datatype="Desktop" condition="parameter(classname)=
  <returnType datatype="LocalServer" condition="parameter(classname)=
  <!-- etc -->


Yes, but see, one the one hand I agree that the factory problem is hard to
solve, but on the other hand it’s about the only good reason to have
varying return types.
Allowing multiple static return types only encourages bad practice (but
OpenAjax is not especially about enforcing good practice so I wouldn’t
oppose them) and fails to solve the only case that really matters.
This type of factory is actually very, very common and worth spending some
time investigating.

So let’s see. The way we specify simple types currently, you can pretty
much evaluate the type and get a valid reference to the type constructor,
right? The type really is an expression that resolves to an actual concrete
type/constructor. There is a precedent in JavaScript in terms of name
resolution, so if you could specify a parameter name, even if there is
potential for naming conflict there, you could apply the same rules of
resolution. Here’s something that could work without being too complex:
If you have a factory such as createInstance(type, options), you would
document it like so:
 <method name="createInstance" scope="instance">
    <description>A method that creates an instance of a class and sets
properties on it.</description>
       <parameter name="type" required="true" datatype="Function">
          <description>The constructor of the class to
       <parameter name="options " required="false" datatype="Object">
          <description>An associative array of property values to
    <returns datatype="type">
       <description>The created instance.</description>
The Google sample from Lori’s e-mail is a little more difficult because the
return type is actually not a trivial expression of the parameters but
using a type name instead of a type in factories is so common that we could
include that special case. So here’s what the metadata for the Google
create method could look like:
<method name="create" scope="instance">
    <description>A method that creates an instance of a class from its type
       <parameter name="type" required="true" datatype="String">
          <description>The constructor of the class to
    <returns datatype="type">
       <description>The created instance.</description>

The type specification for the return type here still is “type”, but the
IDE can look at the type for that parameter and infer what it should do
from it: if it’s a function, use that as the constructor, and if it’s a
string, evaluate that string to get the actual type (when the value is
known, which is the case when it’s a string literal).
I realize this increases the complexity of the spec somehow but it is *a
lot* more useful than multiple return types (which also comes with added

From: Jon Ferraiolo [mailto:jferrai at us.ibm.com]
Sent: Friday, August 29, 2008 12:59 AM.
To: Bertrand Le Roy
Cc: Bertrand Le Roy; ide at openajax.org; Kevin Lindsey; Lori Hylan-Cho
Subject: RE: [OpenAjaxIDE] API metadata: multiple returns;

Hi Bertrand,
I'm not sure we can solve the factory problem very well other than setting
datatype to Object and allowing the IDE to display the text found in the
<description> tag so that developers can see in words that the Object that
is returned requires complex processing.

Regarding what to do with the multiple return types, I was thinking that
that's up to the tool, but I would expect most tools would concatenate
somehow, perhaps with a divider line between each of the return types, such
as a popup that says the following:

|a - Descriptive text for a
|b - Description text for b
|{type=Object} Descriptive text for the first return type
|{type=String} Descriptive text for the second return type


Inactive hide details for Bertrand Le Roy <Bertrand.Le.Roy at microsoft.com>
Bertrand Le Roy <Bertrand.Le.Roy at microsoft.com>

                         <Ber                                           To 
                         d.Le        Bertrand Le Roy                       
                         .Roy        <Bertrand.Le.Roy at microsoft.com>, Jon  
                         @mic        Ferraiolo/Menlo Park/IBM at IBMUS, Lori  
                         roso        Hylan-Cho <lorihc at aptana.com>         
                         om>                                            cc 
                                     Kevin Lindsey <klindsey at aptana.com>,  
                         08/2        "ide at openajax.org" <ide at openajax.org> 
                         08                                        Subject 
                         7 PM        RE: [OpenAjaxIDE] API metadata:       
                                     multiple returns                      

Plus, what would you do with multiple return types? Merge all members and
present them all?

From: Bertrand Le Roy
Sent: Thursday, August 28, 2008 3:36 PM
To: 'Jon Ferraiolo'; Lori Hylan-Cho
Cc: Kevin Lindsey; ide at openajax.org
Subject: RE: [OpenAjaxIDE] API metadata: multiple returns

Multiple return tags don’t solve the factory problem…

From: ide-bounces at openajax.org [mailto:ide-bounces at openajax.org.] On Behalf
Of Jon Ferraiolo
Sent: Thursday, August 28, 2008 3:28 PM
To: Lori Hylan-Cho
Cc: Kevin Lindsey; ide at openajax.org
Subject: Re: [OpenAjaxIDE] API metadata: multiple returns

Hi Lori,
I have been waiting for someone to bring up <returns>. Our tentative
resolution from six months ago was that we would only allow a single
<returns> element but that it could represent multiple return types via the
pipe symbol (e.g., <returns datatype="String|Object"/> But I now think that
we went the wrong direction and that we should adopt the approach that
Aptana ScriptDoc has taken, where there can be multiple <return> (or
<returnType> or <return-type>) elements. I came to this conclusion when
writing the JSDoc to OpenAjax converter. I'll bet that Aptana noticed the
same thing when writing their sdoc to ScriptDocXML converter.

Besides how this makes conversion from JSDoc or sdoc easier, there is also
the argument that the different return types warrant different
<description> elements (and <remarks>, <title>, <examples>, etc.)

Regarding <seealso>, 1-2 months ago we actually decided to rename the
element to <reference>. The descriptive elements and attributes chapter
shows the new names:

but I neglected to update the other chapters. I have fixed things now.


Inactive hide details for Lori Hylan-Cho <lorihc at aptana.com>Lori Hylan-Cho
<lorihc at aptana.com>

 Lori Hylan-Cho <lorihc at aptana.com>                                        
 Sent by: ide-bounces at openajax.org                                         
 08/28/2008 12:53 PM                                                       
                                                         "ide at openajax.org 
                                                         <ide at openajax.org 
                                                         Kevin Lindsey     
                                                         <klindsey at aptana. 
                                                         [OpenAjaxIDE] API 
                                                         multiple returns  

hi all

I know we've been focusing on the widget[/gadget/mashup] metadata lately,
but at Aptana we're starting to work on implementing the API metadata, and
I have some questions about that. (It seemed like we finished with the API
metadata months ago, but the spec's still pretty short on details and long

The first thing I need guidance on is multiple return types. Currently we
have a <returns> tag that doesn't have a plural container (probably because
the verb "returns" already ends in s). Are we going to allow multiple
<returns> tags as children of <constructor>, <method>, etc.? There are a
couple libraries I can think of off the top of my head that need this --
and one at least will also need a way to indicate which return type applies
to which case. For example, in Google gears, the Factory.create() method
creates various objects based on the string passed to it.

// Instantiate Gears objects
var db = google.gears.factory.create('beta.database');

In this case, db is a Database object, but if I had passed "beta.desktop",
I'd have gotten a Desktop object, "beta.localserver" would have given me a
LocalServer object, etc. It'd be great if the metadata could express a
relationship between the argument and the return value, but I don't have a
good idea of how to do that.

One other issue I have in mapping our current method of describing APIs to
the OAA format is the <seealso> tag. I *think* this is analogous to our
<reference> tag, but as <seealso> (
) seems to have been omitted from the Descriptive elements and attributes
chapter, I'm not sure.


Lori Hylan-Cho
Ajax Wrangler
Aptana, Inc.
lorihc at aptana.com

IDE mailing list
IDE at openajax.org

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