Issue with filters and projections #24

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1. springcomp commented on May 15, 2025

   

   springcomp

   on May 15, 2025

   Last edited by springcomp

   ContributorAuthor

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   The root cause for the issue is that a filter [?…] bracket-specifier ends a projection, whereas a flatten [] bracket-specifier does not. I’m not sure where does this requirement come from.

   Here are the two expressions:

   • Expression 1: [?stack==''].branch[?starts_with(@, 'one')] (this incorrectly raises an invalid-type error). Edit this turns out to be the correct result by design. But this is very counter-intuitive and should probably be fixed by a proposal in the spec.
   • Expression 2: [].branch[?starts_with(@, 'one')] this returns [ [ "one/" ], [] ]

   Expression 1 AST

   • Expression 1: [?stack==''].branch[?starts_with(@, 'one')]

   graph TD
     filter --> where_stack
     filter --> identity_
     filter --> function_starts_with
   
     where_stack --> identity
     where_stack --> field_branch
     where_stack --> comparator
   
     comparator --> field_stack
     comparator --> string_empty
     
     function_starts_with --> current
     function_starts_with --> string_one
   

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   JSON representation of the AST

   {
   	"type": "filter_projection",
   	"children": [
   		{
   			"type": "filter_projection",
   			"children": [
   				{
   					"type": "identity",
   					"children": []
   				},
   				{
   					"type": "field",
   					"children": [],
   					"value": "branch"
   				},
   				{
   					"type": "comparator",
   					"children": [
   						{
   							"type": "field",
   							"children": [],
   							"value": "stack"
   						},
   						{
   							"type": "literal",
   							"value": "",
   							"children": []
   						}
   					],
   					"value": "eq"
   				}
   			]
   		},
   		{
   			"type": "identity",
   			"children": []
   		},
   		{
   			"type": "function_expression",
   			"children": [
   				{
   					"type": "current",
   					"children": []
   				},
   				{
   					"type": "literal",
   					"value": "one",
   					"children": []
   				}
   			],
   			"value": "starts_with"
   		}
   	]
   }

   Expression 2 AST

   • Expression 2: [].branch[?starts_with(@, 'one')] this returns [ [ "one/" ], [] ]

   graph TD
     projection --> flatten
   
     flatten --> identity_
     flatten --> filter_projection
   
     filter_projection --> field_branch
     filter_projection --> identity
     filter_projection --> function_starts_with
     
     function_starts_with --> current
     function_starts_with --> string_one
   

   Loading

   JSON representation of the AST

   {
   	"type": "projection",
   	"children": [
   		{
   			"type": "flatten",
   			"children": [
   				{
   					"type": "identity",
   					"children": []
   				}
   			]
   		},
   		{
   			"type": "filter_projection",
   			"children": [
   				{
   					"type": "field",
   					"children": [],
   					"value": "branch"
   				},
   				{
   					"type": "identity",
   					"children": []
   				},
   				{
   					"type": "function_expression",
   					"children": [
   						{
   							"type": "current",
   							"children": []
   						},
   						{
   							"type": "literal",
   							"value": "one",
   							"children": []
   						}
   					],
   					"value": "starts_with"
   				}
   			]
   		}
   	]
   }
2. springcomp commented on May 22, 2025

   

   springcomp

   on May 22, 2025

   Last edited by springcomp

   ContributorAuthor

   More actions

   By contrast, JmesPath.Net does not have the bug returns a result. The reason is that JmesPath.NET uses a Lex-Yacc based parser syntax that is different than the Pratt-based parser used in most other implementations. The behaviour (intuitive, but incorrect) is due to the initial lack of deep knowledge for how bracket-specifier were designed.

   There, the ASTs looks like this:

   Expression 1 AST

   • Expression 1 [?stack==''].branch[?starts_with(@, 'one')]

   graph TD
     index_expression --> sub_expression
     index_expression --> filter_projection
   
     sub_expression --> where_stack
     sub_expression --> identifier_branch
   
     where_stack --> equal_operator
   
     equal_operator --> identifier_stack
     equal_operator --> string_empty 
   
     filter_projection --> function_starts_with
     
    function_starts_with --> current
    function_starts_with --> identifier_one
   

   Loading

   Expression 2 AST

   • Expression 2 [].branch[?starts_with(@, 'one')]

   graph TD
     index_expression --> sub_expression
     index_expression --> filter_projection
   
     sub_expression --> flatten
     sub_expression --> identifier_branch
   
     filter_projection --> function_starts_with
     
    function_starts_with --> current
    function_starts_with --> identifier_one
   

   Loading