as a Field, and I want to insert subsubfield3 in the selection set of subfield2. I can do it using transform with quite a lot of boilerplate code, wondering if it's the only way.

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1. AstPrinter allows to print the Field (and any other Node) into a String. Is the opposite possible? I'd like to parse a String into a Field.
\n

I realize that maybe it's not a very common usage of the Field, so let me clarify why I'm asking this: I have different generic GraphQL requests which selectionSet I need to change, and send them to an underlying service. I have access to DataFetchingEnvironment corresponding to these requests, so I retrieve its Field and work with it.

Thanks in advance 🙏 If the functionality is missing but you would consider it useful, I would be able to contribute

graphql.language.Field as its name suggests is the AST representation of graphql query text. And yes it can be parsed into a string with some tricks

The parser does NOT start from a syntax element of field but its can be tricked

    static Field parseField(String sdlField) {\n        String spec = \"\"\" query Foo {\n        $sdlField\n        }\n        \"\"\"\n        def document = parseQuery(spec)\n        def op = document.getDefinitionsOfType(OperationDefinition.class)[0]\n        return op.getSelectionSet().getSelectionsOfType(Field.class)[0] as Field\n    }\n

parseField(\"f(arg : 1) { inner sub selection }\") for example

The thing is Field and graphql.language.SelectionSet is not really a representation of the \"executable notion of a field and its subselection\"

They are the AST syntax elements. For example read https://www.graphql-java.com/blog/deep-dive-merged-fields

{\n   foo\n   foo\n}\n

This is valid AST and will include two graphql.language.Field objects but there is only one runtime field

You need some other representation of a \"field and its sub selection\". With the https://github.com/atlassian-labs/nadel (our Atlassian federated query engine) we use graphql.normalized.ExecutableNormalizedField and graphql.normalized.ExecutableNormalizedOperation - this is a more complete representation of the \"runtime\" when you take out the syntactical elements

You can mutate this structure and then \"print\" a sub document from this to form \"sub operations\"

If you are just wanting to know \"the simple runtime field subselection\" then graphql.schema.DataFetchingEnvironment#getSelectionSet and graphql.schema.DataFetchingFieldSelectionSet is what you want.

See https://www.graphql-java.com/blog/deep-dive-data-fetcher-results

graphql.language.Field usage #4022

Answered by bbakerman

momentary-lapse asked this question in Q&A

graphql.language.Field usage #4022

momentary-lapse

Jun 24, 2025 · 1 comments · 1 reply

Answered by bbakerman Return to top

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momentary-lapse

Jun 24, 2025

Hello! I have a couple of questions about the usage of graphql.language.Field class. Is there a convenient way to inject something into the tree structure of the Field? Let's say I have something like that: field { subfield1 subfield2 { subsubfield1 subsubfield2 } } as a Field, and I want to insert subsubfield3 in the selection set of subfield2. I can do it using transform with quite a lot of boilerplate code, wondering if it's the only way. AstPrinter allows to print the Field (and any other Node) into a String. Is the opposite possible? I'd like to parse a String into a Field. I realize that maybe it's not a very common usage of the Field, so let me clarify why I'm asking this: I have different generic GraphQL requests which selectionSet I need to change, and send them to an underlying service. I have access to DataFetchingEnvironment corresponding to these requests, so I retrieve its Field and work with it. Thanks in advance 🙏 If the functionality is missing but you would consider it useful, I would be able to contribute

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Answered by bbakerman Jun 24, 2025

graphql.language.Field as its name suggests is the AST representation of graphql query text. And yes it can be parsed into a string with some tricks

The parser does NOT start from a syntax element of field but its can be tricked

    static Field parseField(String sdlField) {
        String spec = """ query Foo {
        $sdlField
        }
        """
        def document = parseQuery(spec)
        def op = document.getDefinitionsOfType(OperationDefinition.class)[0]
        return op.getSelectionSet().getSelectionsOfType(Field.class)[0] as Field
    }

parseField("f(arg : 1) { inner sub selection }") for example

The thing is Field and graphql.language.SelectionSet is not really a represen…

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bbakerman

Jun 24, 2025

Collaborator

graphql.language.Field as its name suggests is the AST representation of graphql query text. And yes it can be parsed into a string with some tricks The parser does NOT start from a syntax element of field but its can be tricked static Field parseField(String sdlField) { String spec = """ query Foo { $sdlField } """ def document = parseQuery(spec) def op = document.getDefinitionsOfType(OperationDefinition.class)[0] return op.getSelectionSet().getSelectionsOfType(Field.class)[0] as Field } parseField("f(arg : 1) { inner sub selection }") for example The thing is Field and graphql.language.SelectionSet is not really a representation of the "executable notion of a field and its subselection" They are the AST syntax elements. For example read https://www.graphql-java.com/blog/deep-dive-merged-fields { foo foo } This is valid AST and will include two graphql.language.Field objects but there is only one runtime field You need some other representation of a "field and its sub selection". With the https://github.com/atlassian-labs/nadel (our Atlassian federated query engine) we use graphql.normalized.ExecutableNormalizedField and graphql.normalized.ExecutableNormalizedOperation - this is a more complete representation of the "runtime" when you take out the syntactical elements You can mutate this structure and then "print" a sub document from this to form "sub operations" If you are just wanting to know "the simple runtime field subselection" then graphql.schema.DataFetchingEnvironment#getSelectionSet and graphql.schema.DataFetchingFieldSelectionSet is what you want. See https://www.graphql-java.com/blog/deep-dive-data-fetcher-results

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momentary-lapse Jun 25, 2025

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Thanks much for the explanation and this code snippet! Yeah, I'm aware of the merged fields in AST. We're expecting our API to be used only internally, so for now I need "the simple runtime field subselection", and access it with something likeDataFetchingEnvironment.getMergedField().getSingleField(). We're bounded to this DataFetchingEnvironment class because of DGS framework, their fetchers are exposing it for particular fields and operations. But will take a look into ExecutableNormalizedOperation as well.

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