[jira] [Commented] (AVRO-1872) Using union in nodejs, when has several different names in the union's record will report the Error at this time: ambiguous unwrapped the union, but the same protocol in Java: no problem

["Matthieu Monsch (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AVRO-1872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15355310#comment-15355310 ] 

Matthieu Monsch commented on AVRO-1872:
---------------------------------------

TL;DR: This isn't a bug, it'll work if you set the `wrapUnions` flag when parsing the protocol (e.g. `parse('./Test.avpr', {wrapUnions: true})`).

JavaScript types don't map perfectly to Avro types. For example, we can distinguish between values of type `int` and values of type `string`, but not always between `int` and `double`. This can lead to data corruption when encoding unions (since we might not be able to correctly infer the active branch). For the majority of unions, this isn't a problem and using the natural "unwrapped" representation is a good choice. However, in cases where two or more branches are alike, this representation isn't good enough and parsing the schema will fail rather than risk corrupting data. The simplest option is then to use the `wrapUnions` flag to fall back to the "wrapped" representation (similar to unions' JSON encoding), which is less convenient but always correct. If you are curious, you can read more about this here - https://github.com/mtth/avsc/wiki/API#class-unwrappeduniontypeattrs-opts .

> Using union in nodejs, when has several different names in the union's record will report the Error at this time: ambiguous unwrapped the union, but the same protocol in Java: no problem
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: AVRO-1872
>                 URL: https://issues.apache.org/jira/browse/AVRO-1872
>             Project: Avro
>          Issue Type: Bug
>          Components: java, javascript, js
>    Affects Versions: 1.8.1
>         Environment: node.js
>            Reporter: Chunfy.Tseng
>
> protocol eg:
> {
>     "protocol": "Test",
>     "namespace": "test.avro",
>     "types": [
>         {
>             "type": "record",
>             "name": "AAA",
>             "fields": [
>                 {
>                     "name": "a",
>                     "type": "string"
>                 }
>             ]
>         },
>         {
>             "type": "record",
>             "name": "BBB",
>             "fields": [
>                 {
>                     "name": "b",
>                     "type": "string"
>                 },
>                 {
>                     "name": "a",
>                     "type": "AAA"
>                 }
>             ]
>         },
>         {
>             "type": "record",
>             "name": "CCC",
>             "fields": [
>                 {
>                     "name": "c",
>                     "type": "string"
>                 },
>                 {
>                     "name": "t",
>                     "type": "int"
>                 }
>             ]
>         },
>         {
>             "type": "record",
>             "name": "DDD",
>             "fields": [
>                 {
>                     "name": "temp",
>                     "type": "string"
>                 },
>                 {
>                     "name": "d",
>                     "type": [
>                         "null",
>                         "BBB",
>                         "CCC"
>                     ]
>                 }
>             ]
>         }
>     ],
>     "messages": {}
> }
> in java use cmd:java -jar  D:\workspace-mars2\Avro\lib\avro-tools-1.8.1.jar compile protocol D:\new\Test.avpr D:\new    is ok.
> but in node.js code:
> var avro = require("D:\\Soft\\nodejs\\node_modules\\avsc");
> var protocol = avro.parse("./Test.avpr");
> Prompt error message as below:
> D:\Soft\nodejs\node_modules\avsc\lib\types.js:918
>         throw new Error(f('ambiguous unwrapped union: %j', this));
> Error: ambiguous unwrapped union:["null",{"name":"test.avro.BBB","type":"record","fields":[{"name":"b","type":"string","order":"ascending","aliases":[]},{"name":"a","type":{"name":"test.avro.AAA","type":"record","fields":[{"name":"a","type":"string","order":"ascending","aliases":[]}],"aliases":[]},"order":"ascending","aliases":[]}],"aliases":[]},{"name":"test.avro.CCC","type":"record","fields":[{"name":"c","type":"string","order":"ascending","aliases":[]},{"name":"t","type":"int","order":"ascending","aliases":[]}],"aliases":[]}]
> it is bug?



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