[Duplicate imports] Fix issue that would cause duplicate imports

[rcancro]

In the given schema file, we can see the class board_activity references itself:

{
    "id": "board_activity.json",
    "title": "board_activity",
    "description": "Schema definition of a BoardActivity",
    "$schema": "http://json-schema.org/schema#",
    "type": "object",
    "properties": {
      "ref_board_activity": { "$ref": "board_activity.json" },
    },
}

This causes multiple BoardActivity imports in BoardActivity.m. The issue is in ObjCIR.Root.imports renderImplementation method. This is how the imports are being generated:

case .imports(let classNames, let myName, _):
    return [classNames.union(Set([myName]))
        .sorted()
        .map { $0.trimmingCharacters(in: .whitespaces) }
        .map { ObjCIR.fileImportStmt($0, headerPrefix: params[GenerationParameterType.headerPrefix]) }
        .joined(separator: "\n")]

Using the schema above, classNames would include “BoardActivity “. Note the space. myName would be ”BoardActivity”. Note the lack of space.

These two get unioned together in a set. The result is ["BoardActivity ", "BoardActivity"]. We sort this set, then remove any trailing spaces. But at this point we are an array, and we now have two duplicate entries in our array: ["BoardActivity", "BoardActivity"]. This leads plank to render #import "BoardActivity.h" twice in our implementation file.

A solution would be to trim these strings BEFORE the union:

case .imports(let classNames, let myName, _):
    let strippedClassNames = Set(classNames.map { $0.trimmingCharacters(in: .whitespaces) })
    return [strippedClassNames.union(Set([myName.trimmingCharacters(in: .whitespaces)]))
        .sorted()
        .map { ObjCIR.fileImportStmt($0, headerPrefix: params[GenerationParameterType.headerPrefix]) }
        .joined(separator: "\n")]

I created strippedClassNames which holds the trimmed classNames. This gets unioned that with the stripped version of myName to get the list of imports. Now we end up with the array only have one entry ["BoardActivity"].

Note: I also made a change in ObjectiveCNSCodingExtension.swift because the compiler was telling me that the return value was too complicated for it to figure out.