[2021-01-07] Review "RFC: Assert subscription field is not introspection. #2861"

[benjie]

Ivan has some concerns about the complexity of the JS implementation, but agrees with the spec changes.
ACTION - Ivan: thorough review of the PR

PR to review: graphql/graphql-js#2861

• assignee(s): @IvanGoncharov
• source: https://github.com/graphql/graphql-wg/blob/master/notes/2021-01-07.md#advancing-no-introspection-at-root-of-subscription-operation-10m-benjie

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[benjie]

Ivan has approved this PR (but not yet merged it, pending potential refactoring).