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Error decoding nested JSON with missing container #40
Description
Hi there!
Big thanks for this package, I've really been enjoying it!
I have an issue when decoding nested JSON when one level of the keys doesn't exist.
I have this struct:
@Codable
struct Avatar {
@CodedAt("avatar", "url")
let url: URL?
}Trying to decode this works fine.
func testConditionalAndNestedOptionalCodingWorking() throws {
let jsonStr = """
{
"avatar": {
"url": "https://example.com/"
}
}
"""
let json = try XCTUnwrap(jsonStr.data(using: .utf8))
let model = try JSONDecoder().decode(Avatar.self, from: json)
XCTAssertEqual(model.url, URL(string: "https://example.com/"))
}Decoding JSON with a value for "url" also works.
func testConditionalAndNestedOptionalCoding() throws {
let jsonStr = """
{
"avatar": {
"url": null
}
}
"""
let json = try XCTUnwrap(jsonStr.data(using: .utf8))
let model = try JSONDecoder().decode(Avatar.self, from: json)
XCTAssertEqual(model.url, nil)
}The problem is when the "avatar" value is null.
func testMissingContainer() throws {
let jsonStr = """
{
"avatar": null
}
"""
let json = try XCTUnwrap(jsonStr.data(using: .utf8))
let model = try JSONDecoder().decode(Avatar.self, from: json)
XCTAssertEqual(model.url, nil)
}Since my struct has an optional type for the url property, I would expect it to ignore the missing container and fallback to setting the value as nil. Instead, I get back an error:
typeMismatch(Swift.Dictionary<Swift.String, Any>, Swift.DecodingError.Context(codingPath: [], debugDescription: "Expected to decode Dictionary<String, Any> but found a null value instead.", underlyingError: nil))
I tried setting a default value using @Default(nil as URL?) but that didn't seem to work.
Anything I'm missing here or is this a bug?
Thanks again for the package!
Activity
soumyamahunt commentedon Nov 8, 2023
Thanks, this is a good find!
Currently
MetaCodableonly uses fallback only if the last key decoding fails. This is a bug and the fix is going to be a bit tricky.