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https://issues.apache.org/jira/browse/CB-12218?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16307647#comment-16307647
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Hideto KIHARA commented on CB-12218:
------------------------------------
There are two routes which uses different message encoding on native to JS
message.
(on EvalBridgeMode)
If route2 is used, null becomes "".
Because popAndEncodeJs() does not support null.
{noformat}
* route1 (popAndEncode()):
CordovaBridge#jsExec()
-> [plugin calls CallbackContext#sendPluginResult()]
-> NativeToJsMessageQueue#popAndEncode()
* route2 (popAndEncodeJs()):
CordovaBridge#jsExec()
-> [plugin starts new thread and returns immediately from execute()]
-> (NativeToJsMessageQueue#popAndEncode(). no message in queue yet)
-> [plugin thread calls CallbackContext#sendPluginResult()]
-> EvalBridgeMode#onNativeToJsMessageAvailable()
-> NativeToJsMessageQueue#popAndEncodeJs()
{noformat}
null becomes "" by JSONObject.quote(null) in PluginResult#getMessage().
(It may be better to add a method calculateJsEncodedLength().
Because calculateEncodedLength() does not consider encodeAsJsMessage())
I wrote sample plugin and cordova-paramedic tests to reproduce this issue:
https://github.com/deton/cordova-plugin-nullresulttest
> inconsistent null handling between EVAL and ONLINE bridge modes
> ---------------------------------------------------------------
>
> Key: CB-12218
> URL: https://issues.apache.org/jira/browse/CB-12218
> Project: Apache Cordova
> Issue Type: Bug
> Components: cordova-android
> Affects Versions: 6.0.0
> Environment: Android
> Reporter: Alan Kinzie
> Assignee: Joe Bowser
> Attachments: CB12218.zip
>
>
> If the Android native code invokes the success callback like this:
> callbackContext.success(null);
> then the value given to the javascript callback changes depending on the
> bridge type used.
> If the ONLINE_EVENT type is used, then null will be passed to the javascript
> callback.
> ie: if result is the parameter of the javascript success callback then
> result === null // will be true
> result === "" // will be false
> If the EVAL_BRIDGE type is used, then an empty string will be passed to the
> javascript callback.
> ie: if result is the parameter of the javascript success callback then
> result === null // will be false
> result === "" // will be true
> The value of the parameter given to the success callback should not change
> depending on the bridge type. Since ONLINE_EVENT was the default before
> cordova android 6.0.0, I am inclined to think the ONLINE bridge is doing the
> correct behaviour. Also, converting null to an empty string loses
> information. Therefore I think the EVAL mode should to be changed to be
> consistent with the ONLINE mode.
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