custom-connector-example build failed

[goyalrajat]

Could not resolve dependencies for project software.amazon.appflow:custom-connector-example:jar:1.0.9: The following artifacts could not be resolved: software.amazon.appflow:aws-custom-connector-sdk:jar:1.0.9, software.amazon.appflow:aws-custom-connector-queryfilter:jar:1.0.9, software.amazon.appflow:aws-custom-connector-integ-test:jar:1.0.9:

[JamieWT]

Are you building this on Windows? I found that the build fails on windows, but builds fine on Linux (under WSL2). It probably builds fine on Macs too.

The issues with windows are:

1. There are a lot of checkstyle issues with the code generated by antrl, so this code needs to be excluded from checkstyle checks. The file checkstyle-suppressions.xml does this, but the path expression doesn't work on windows.
   Changing
   <suppress files="[/\\]com/amazonaws/appflow/custom/connector/queryfilter/antlr[/\\]" checks=".*" />
   to
   <suppress files="[\\/]com[\\/]amazonaws[\\/]appflow[\\/]custom[\\/]connector[\\/]queryfilter[\\/]antlr[\\/]" checks=".*" />
   fixes this problem.

2. When doing the build I got an exception

org.junit.platform.commons.JUnitException: TestEngine with ID 'junit-jupiter' failed to discover tests  
...  
Caused by: java.lang.NoClassDefFoundError: com/amazonaws/appflow/custom/connector/queryfilter/antlr/CustomConnectorQueryFilterParser$LimitExpressionContext (wrong name: com/amazonaws/appflow/custom/connector/queryfilter/antlr/CustomConnectorQueryFilterParser$LimitexpressionContext)

Note the "$LimitExpressionContext" and "$LimitexpressionContext" differ by a lowercase/uppercase 'e'.
This is caused by this evil code in com/amazonaws/appflow/custom/connector/queryfilter/antlr/CustomConnectorQueryFilterParser.java:

CustomConnectorQueryFilterParser has two nested classes that have the same name but a different case. This is fine on unix-based OSs with case-sensitive file names, but on Windows one class overwrites the other.

This is code generated by antlr. To fix, edit custom-connector-queryfilter/src/main/configuration/grammar/CustomConnectorQueryFilterParser.g4 and change:

limitexpression  
: op=limit right=count                     #limitExpression  
| left=expression op=limit right=count     #limitExpression  // SQL 'LIMIT xyz' operator  
;

to

limitexpression  
: op=limit right=count                     // #limitExpression  
| left=expression op=limit right=count     // #limitExpression  // SQL 'LIMIT xyz' operator  
;

Then everything builds successfully

[INFO] Reactor Summary for Amazon AppFlow Custom Connector SDK 1.0.9:
[INFO]
[INFO] Amazon AppFlow Custom Connector SDK ................ SUCCESS [  9.968 s]
[INFO] aws-custom-connector-sdk ........................... SUCCESS [ 37.525 s]
[INFO] aws-custom-connector-queryfilter ................... SUCCESS [ 11.492 s]
[INFO] aws-custom-connector-integ-test .................... SUCCESS [ 16.459 s]
[INFO] custom-connector-example ........................... SUCCESS [ 18.625 s]
[INFO] custom-connector-tests ............................. SUCCESS [  9.895 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS

NOTE: I've not deployed a connector with that antlr grammar change, so consider that change untested.