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Better DDB expressions support2: ExpressionTree

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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.
This commit is contained in:
pvbouwel 2020-04-11 21:17:16 +01:00
commit 9ed613e197
10 changed files with 2317 additions and 13 deletions
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16
tests/test_dynamodb2/test_dynamodb_table_with_range_key.py
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@ -1254,14 +1254,22 @@ def test_update_item_with_expression():
item_key = {"forum_name": "the-key", "subject": "123"}
table.update_item(Key=item_key, UpdateExpression="SET field=2")
table.update_item(
Key=item_key,
UpdateExpression="SET field = :field_value",
ExpressionAttributeValues={":field_value": 2},
)
dict(table.get_item(Key=item_key)["Item"]).should.equal(
{"field": "2", "forum_name": "the-key", "subject": "123"}
{"field": Decimal("2"), "forum_name": "the-key", "subject": "123"}
)
table.update_item(Key=item_key, UpdateExpression="SET field = 3")
table.update_item(
Key=item_key,
UpdateExpression="SET field = :field_value",
ExpressionAttributeValues={":field_value": 3},
)
dict(table.get_item(Key=item_key)["Item"]).should.equal(
{"field": "3", "forum_name": "the-key", "subject": "123"}
{"field": Decimal("3"), "forum_name": "the-key", "subject": "123"}
)