SourceKitten not reporting function substructure when only instance variable is changed

[KaneCheshire]

We have an issue with the latest version of SwiftLint and it seems as though it is because of a bug with SourceKitten itself. This has only manifested since updating to the latest version of SwiftLint, which is also using the latest version of SourceKitten.

TL;DR:

When provided with the following code:

class TotoTests: XCTestCase {
    var foo: String = ""

    override func setUp() {
        foo = "bar"
    }
}

SourceKitten does not report any substructure for the setUp() function, despite containing valid code in there.

More info

I've put together a test case which shows the issue:

func testBug() throws {
        let contents = "class TotoTests: XCTestCase {\n    var foo: String = \"\"\n    override func setUp() {\n        foo = \"bar\"\n    }\n}"

        let structure = try Structure(file: .init(contents: contents))
        let substructureArray = try XCTUnwrap(structure.dictionary["key.substructure"] as? [SourceKitRepresentable])
        let substructureDictionary = try XCTUnwrap(substructureArray.first as? [String : SourceKitRepresentable])

        let typeName = try XCTUnwrap(substructureDictionary["key.name"] as? String)
        XCTAssertEqual(typeName, "TotoTests")

        let typeSubstructureArray = try XCTUnwrap(substructureDictionary["key.substructure"] as? [SourceKitRepresentable])
        XCTAssertEqual(typeSubstructureArray.count, 2) // Only has one property and one function

        let propertySubstructureDictionary = try XCTUnwrap(typeSubstructureArray[0] as? [String: SourceKitRepresentable])
        let propertyName = try XCTUnwrap(propertySubstructureDictionary["key.name"] as? String)
        XCTAssertEqual(propertyName, "foo")

        let functionSubstructureDictionary = try XCTUnwrap(typeSubstructureArray[1] as? [String: SourceKitRepresentable])
        let functionName = try XCTUnwrap(functionSubstructureDictionary["key.name"] as? String)
        XCTAssertEqual(functionName, "setUp()")

        let functionContentsArray = try XCTUnwrap(functionSubstructureDictionary["key.substructure"] as? [SourceKitRepresentable])
        XCTAssertEqual(functionContentsArray.count, 1)
    }

Just to validate, if you change the contents to this:

let contents = "class TotoTests: XCTestCase {\n    var foo: String = \"\"\n    override func setUp() {\n        let foo = \"bar\"\n    }\n}"

Then the test passes fine. It's only an issue when setting an instance variable, rather than a local variable:

Additionally a similar issue was raised on the SwiftLint repo which I believe to be because of the same issue in SourceKitten.

I hope this helps debug, I don't know much more about SourceKitten but I can try and take a look at fixing too, but raising here because likely the code owner(s) will be able to fix it faster :)

[KaneCheshire]

Oh I should also say, this is running the tests in Xcode 12.5.1, I haven't tried any other versions or toolchains.

[johnfairh]

The Structure API in SourceKitten makes a single query to SourceKit, source.request.editor.open, and returns the doc structure results without modification. You could check on the Swift nightly toolchain: if it's still a problem then the question -- something like "Assignment expressions missing from doc structure' belongs with the Swift project.

[KaneCheshire]

Okay thanks for getting back to me, I notice it does pick up if you do foo = String() so guess it's a Swift issue then

[johnfairh]

Right -- just for interest, notice there you get just a source.lang.swift.expr.call inside the substructure which is the String() part -- the assignment part itself is not mentioned.