Part of structured approach for UpdateExpressions:
1) Expression gets parsed into a tokenlist (tokenized)
2) Tokenlist get transformed to expression tree (AST)
3) The AST gets validated (full semantic correctness) -> this commit
4) AST gets processed to perform the update
This commit uses the AST to perform validation. Validation makes sure the
nodes encounterd have valid values and they will also resolve values for
references that refer to item state or values passed into the expression.
Part of structured approach for UpdateExpressions:
1) Expression gets parsed into a tokenlist (tokenized)
2) Tokenlist get transformed to expression tree (AST) -> This commit
3) The AST gets validated (full semantic correctness)
4) AST gets processed to perform the update
This commit uses the tokenlist to build an expression tree. This tree is not
yet used. Still it allows to raise additional Validation Exceptions which
previously were missed silently therefore it allows tests to catch these type of
ValidationException. For that reason DDB UpdateExpressions will be parsed
already. It also makes sure we won't break existing tests.
One of the existing tests had to be changed in order to still pass:
- test_dynamodb_table_with_range_key.test_update_item_with_expression
This test passed in a numeric literal which is not supported by DynamoDB
and with the current tokenization it would get the same error as in AWS
DynamoDB.
