Modify query programmatically

Sent here from https://github.com/graphql-python/gql/issues/272

There is a way in gql to construct queries programmatically with DSL module or by parsing a string into AST with gql.gql() and then using print_ast from graphql to get back the string.

import gql

dg = gql.gql("""
    query getContinents {
      continents {
        code
        name
      }
    }
""")

from graphql import print_ast
print(print_ast(dg))

What is not clear is how to actually find nodes in AST and edit or expand them. For example, finding a parent of node in the query below (continents) and adding an attribute to it ((code:"AF")).

query getContinents {
  continents {
    code
    name
  }
}

So that the query becomes.

    query getContinents {
      continents (code:"AF") {
        code
        name
      }
    }

I looked into the docs, but it doesn’t actually explain.

• How to find AST node that needs modification?
• How to modify it (upsert attributes)?

The documentation container chapter about schemas https://graphql-core-3.readthedocs.io/en/latest/usage/extension.html?highlight=modify ast#extending-a-schema and as I am new to GraphQL I am not yet sure if schema and query are the same things.

Feature requests

I am not sure GraphQL.js includes this too and not sure that fundamentally changes the way GraphQL works.

[Cito]

@abitrolly I’m currently going through the old tickets before creating the next release. Feel free to reopen or open a new issue if you have concrete questions.

[Cito]

@abitrolly You can use a Visitor to traverse the AST. This will also give you access to the immediate parent and full list of ancestors of the current node.

Here is an example of a visitor that searches for a field node with the name ‘code’, and then adds another field node with the name ‘newField’ to its parent.

from graphql import FieldNode, NameNode, Visitor, parse, print_ast, visit
from graphql.pyutils import FrozenList

query = """
query getContinents {
  continents {
    code
    name
  }
}"""

doc = parse(query)

class ExampleVisitor(Visitor):

    def enter_name(self, node, key, parent, path, ancestors):
        if node.value == 'code' and parent.kind == 'field':
            parent = ancestors[-2]  # selection set
            parent.selections = FrozenList(
                (*parent.selections,
                 FieldNode(name=NameNode(value='newField'))))
            return True  # stop visiting

visitor = ExampleVisitor()
visit(doc, visitor)

new_query = print_ast(doc)

print(new_query)

Note: It is recommended to use a FrozenList instead of an ordinary list to make the nodes hashable.