Fix duplicate indentifiers in import statements

[cahilfoley]

Related #3990

I had a look into issue #3990 as I was experiencing the same symptoms, the fix proposed in this comment did not work for me as the imports are generated in the visitor-plugin-common package.

In my case it seemed like duplicate fragment identifiers were only generated sometimes, for example I would get something like the below in my generated files (unfortunately it's an internal codebase that I'm not able to share - I believe this comment references a codebase that can reproduce the bug):

import {
  aFieldsFragment, // used multiple times in the queries, single import
  bFieldsFragment, // also used multiple times in the query, import duplicated belowk,,,,
  cFieldsFragment,
  bFieldsFragment,
  cFieldsFragment,
  dFieldsFragment,
} from '../../services/queries.generated'

This change deduplicates the list of import identifiers prior to being joined in the import statement. After making the change I get the expected, valid import statement generated.

[dotansimha]

Perfect :) thanks @cahilfoley !

[theguild-bot]

The latest changes of this PR are available as alpha in npm: 1.15.2-alpha-2030312e.0

Quickly update your package.json by running:

npx match-version @graphql-codegen 1.15.2-alpha-2030312e.0