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Make enumerateAsDict() Accept a Throwing Function #139

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Make enumerateAsDict() Accept a Throwing Function #139

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22 changes: 15 additions & 7 deletions SwiftCSV/Parser.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ extension CSV {
try Parser.enumerateAsArray(text: self.text, delimiter: self.delimiter, startAt: startAt, rowLimit: rowLimit, rowCallback: rowCallback)
}

public func enumerateAsDict(_ block: @escaping ([String : String]) -> ()) throws {
public func enumerateAsDict(_ block: @escaping ([String : String]) throws -> ()) throws {

try Parser.enumerateAsDict(header: self.header, content: self.text, delimiter: self.delimiter, block: block)
}
Expand Down Expand Up @@ -60,7 +60,7 @@ enum Parser {
delimiter: CSVDelimiter,
startAt offset: Int = 0,
rowLimit: Int? = nil,
rowCallback: @escaping ([String]) -> ()) throws {
rowCallback: @escaping ([String]) throws -> ()) throws {
let maxRowIndex = rowLimit.flatMap { $0 < 0 ? nil : offset + $0 }

var currentIndex = text.startIndex
Expand All @@ -72,7 +72,7 @@ enum Parser {

var rowIndex = 0

func finishRow() {
func finishRow() throws {
defer {
rowIndex += 1
fields = []
Expand All @@ -81,7 +81,11 @@ enum Parser {

guard rowIndex >= offset else { return }
fields.append(String(field))
rowCallback(fields)
do {
try rowCallback(fields)
} catch {
throw CSVParseError.generic(message: "Error thrown by block for row \(rowIndex)")
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You're right, this doesn't change usage because the function is throwing anyway.

But could you avoid catching, wrapping, and rethrowing the error? User code throwing a MyVerySpecificError on failure in this callback will likely want to work with and maybe even catch MyVerySpecificError, not CSVParseError.generic, losing the original error's information completely here.

For context: I'm also not a fan of wrapping-and-rethrowing, because that adds another step to the debugging flow when you need to inspect the stack.

Just let rowCallback's error propagate will do The Right Thing in more cases 👍

}
}

var state: ParsingState = ParsingState(
Expand Down Expand Up @@ -118,12 +122,16 @@ enum Parser {
}

if !fields.isEmpty {
rowCallback(fields)
do {
try rowCallback(fields)
} catch {
throw CSVParseError.generic(message: "Error thrown by block for row \(rowIndex)")
}
Comment on lines +125 to +129
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Same as above here, please:

Suggested change
do {
try rowCallback(fields)
} catch {
throw CSVParseError.generic(message: "Error thrown by block for row \(rowIndex)")
}
try rowCallback(fields)

}
}
}

static func enumerateAsDict(header: [String], content: String, delimiter: CSVDelimiter, rowLimit: Int? = nil, block: @escaping ([String : String]) -> ()) throws {
static func enumerateAsDict(header: [String], content: String, delimiter: CSVDelimiter, rowLimit: Int? = nil, block: @escaping ([String : String]) throws -> ()) throws {

let enumeratedHeader = header.enumerated()

Expand All @@ -133,7 +141,7 @@ enum Parser {
for (index, head) in enumeratedHeader {
dict[head] = index < fields.count ? fields[index] : ""
}
block(dict)
try block(dict)
}
}
}
10 changes: 5 additions & 5 deletions SwiftCSV/ParsingState.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -20,12 +20,12 @@ struct ParsingState {
private(set) var innerQuotes = false

let delimiter: Character
let finishRow: () -> Void
let finishRow: () throws -> Void
let appendChar: (Character) -> Void
let finishField: () -> Void

init(delimiter: Character,
finishRow: @escaping () -> Void,
finishRow: @escaping () throws -> Void,
appendChar: @escaping (Character) -> Void,
finishField: @escaping () -> Void) {

Expand All @@ -44,7 +44,7 @@ struct ParsingState {
} else if char == delimiter {
finishField()
} else if char.isNewline {
finishRow()
try finishRow()
} else if char.isWhitespace {
// ignore whitespaces between fields
} else {
Expand Down Expand Up @@ -72,7 +72,7 @@ struct ParsingState {
atStart = true
parsingField = false
innerQuotes = false
finishRow()
try finishRow()
} else {
appendChar(char)
}
Expand All @@ -91,7 +91,7 @@ struct ParsingState {
atStart = true
parsingQuotes = false
innerQuotes = false
finishRow()
try finishRow()
} else if char.isWhitespace {
// ignore whitespaces between fields
} else {
Expand Down