Error when reading typedef from file in V2.6.6

[ais-one]

Package Name & Version

The issue is present in apollo-server-express, the latest version (2.6.6).

Latest version where the problem did not occur

My previous version was 2.6.3

Expected Behavior

gql schema can load from file

Actual Behavior

The following fatal error occurs

TypeError: Cannot read property 'some' of undefined

Repo demonstrating the problem

https://github.com/ais-one/apollo-express-test
It's a simple example showing how to replicate the problem

[mrsunboss]

Maybe is this problem => #2924

[jesstelford]

See also #2753

[abernix]

Thank you @mrsunboss for tracking down the issue and opening the appropriate PR to fix the problem. This subtle but positive triaging, linking and fixing is well received and great for the project, so thank you!

This was introduced by an unguarded property access in #2762. TypeScript offers us a lot of protections, and seemed to indicate that there was nothing to worry about, but TypeScript is still is no substitute for defensive coding.

Tests help protect all involved here, both on our side, and on the side of our consumers — who should, as a best practice — have integration tests in place to make sure their production expectations and needs are met.

On top of @mrsunboss's #2924, I've added a regression test for this in 32deb9f, a further defense for another explored possibility in 490c93a and updated the ApolloServer constructor types with 77207ff, which was ultimately most at fault for allowing this regression to occur, since JavaScript users do still pass string typeDefs (those not wrapped with the gql tag) as a matter of historical fact.

I'll release 2.6.7 soon with the fix.