On fail should only be allowed with regular-compound-stmt

[pcnfernando]

Description:
Ref https://ballerina.io/spec/lang/master/#stmt-with-on-fail

Steps to reproduce:

Affected Versions:
2201.1.1

OS, DB, other environment details and versions:

Related Issues (optional):

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[gayalkuruppu]

For now TransactionStatementNode and RetryStatementNode has an Optional<OnFailClauseNode> onFailClause() and the on fail is allowed.

[pcnfernando]

Original impl based on ballerina-platform/ballerina-spec#337 (comment)

[buehlefs]

What is the reason on fail support is removed for transactions? Updating the spec to specifically support it for transaction blocks could also be an option here, as there is a clear use case for this feature.

For example, I use this extensively to streamline error handling of transaction blocks (since all my database calls are wrapped in transactions anyway). The alternatives to this are:

• Checking every single result for errors -> ~1 extra if statement per result
• Wrapping the transaction in a do block with on fail -> one extra level of nesting
• Refactoring the transactions into individual functions -> the best choice but creates many single-use functions just for better error handling

The on fail of transaction blocks could also be interpreted as syntactic sugar for do { transaction {...} } on fail .... This could be useful to simplify defining the semantics in combination with retry of transactions.

[SasinduDilshara]

Had a chat with internal team and decided to allow on fail for transaction and retry statements

[github-actions]

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