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Merge pull request swiftlang#619 from mlavergn/trailingCommas
Add option to disable trailing commas on multi-line collections
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6 files changed

+324
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‎Documentation/Configuration.md

+3
Original file line numberDiff line numberDiff line change
@@ -82,6 +82,9 @@ top-level keys and values:
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* `spacesAroundRangeFormationOperators` _(boolean)_: Determines whether whitespace should be forced
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before and after the range formation operators `...` and `..<`.
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85+
* `multiElementCollectionTrailingCommas` _(boolean)_: Determines whether multi-element collection literals should have trailing commas.
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Defaults to `true`.
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> TODO: Add support for enabling/disabling specific syntax transformations in
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> the pipeline.
8790

‎Sources/SwiftFormat/API/Configuration+Default.swift

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Original file line numberDiff line numberDiff line change
@@ -37,5 +37,6 @@ extension Configuration {
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self.indentSwitchCaseLabels = false
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self.spacesAroundRangeFormationOperators = false
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self.noAssignmentInExpressions = NoAssignmentInExpressionsConfiguration()
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self.multiElementCollectionTrailingCommas = true
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}
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}

‎Sources/SwiftFormat/API/Configuration.swift

+29
Original file line numberDiff line numberDiff line change
@@ -42,6 +42,7 @@ public struct Configuration: Codable, Equatable {
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case rules
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case spacesAroundRangeFormationOperators
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case noAssignmentInExpressions
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case multiElementCollectionTrailingCommas
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}
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/// A dictionary containing the default enabled/disabled states of rules, keyed by the rules'
@@ -162,6 +163,29 @@ public struct Configuration: Codable, Equatable {
162163
/// Contains exceptions for the `NoAssignmentInExpressions` rule.
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public var noAssignmentInExpressions: NoAssignmentInExpressionsConfiguration
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/// Determines if multi-element collection literals should have trailing commas.
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///
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/// When `true` (default), the correct form is:
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/// ```swift
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/// let MyCollection = [1, 2,]
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/// ...
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/// let MyCollection = [
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/// "a": 1,
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/// "b": 2,
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/// ]
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/// ```
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///
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/// When `false`, the correct form is:
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/// ```swift
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/// let MyCollection = [1, 2]
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/// ...
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/// let MyCollection = [
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/// "a": 1,
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/// "b": 2
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/// ]
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/// ```
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public var multiElementCollectionTrailingCommas: Bool
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/// Constructs a Configuration by loading it from a configuration file.
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public init(contentsOf url: URL) throws {
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let data = try Data(contentsOf: url)
@@ -239,6 +263,10 @@ public struct Configuration: Codable, Equatable {
239263
try container.decodeIfPresent(
240264
NoAssignmentInExpressionsConfiguration.self, forKey: .noAssignmentInExpressions)
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?? defaults.noAssignmentInExpressions
266+
self.multiElementCollectionTrailingCommas =
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try container.decodeIfPresent(
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Bool.self, forKey: .multiElementCollectionTrailingCommas)
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?? defaults.multiElementCollectionTrailingCommas
242270

243271
// If the `rules` key is not present at all, default it to the built-in set
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// so that the behavior is the same as if the configuration had been
@@ -271,6 +299,7 @@ public struct Configuration: Codable, Equatable {
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try container.encode(fileScopedDeclarationPrivacy, forKey: .fileScopedDeclarationPrivacy)
272300
try container.encode(indentSwitchCaseLabels, forKey: .indentSwitchCaseLabels)
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try container.encode(noAssignmentInExpressions, forKey: .noAssignmentInExpressions)
302+
try container.encode(multiElementCollectionTrailingCommas, forKey: .multiElementCollectionTrailingCommas)
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try container.encode(rules, forKey: .rules)
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}
276305

‎Sources/SwiftFormat/PrettyPrint/PrettyPrint.swift

+1-1
Original file line numberDiff line numberDiff line change
@@ -557,7 +557,7 @@ public class PrettyPrinter {
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// We never want to add a trailing comma in an initializer so we disable trailing commas on
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// single element collections.
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let shouldHaveTrailingComma =
560-
startLineNumber != openCloseBreakCompensatingLineNumber && !isSingleElement
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startLineNumber != openCloseBreakCompensatingLineNumber && !isSingleElement && configuration.multiElementCollectionTrailingCommas
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if shouldHaveTrailingComma && !hasTrailingComma {
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diagnose(.addTrailingComma, category: .trailingComma)
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} else if !shouldHaveTrailingComma && hasTrailingComma {

‎Sources/_SwiftFormatTestSupport/Configuration+Testing.swift

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Original file line numberDiff line numberDiff line change
@@ -40,6 +40,7 @@ extension Configuration {
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config.indentSwitchCaseLabels = false
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config.spacesAroundRangeFormationOperators = false
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config.noAssignmentInExpressions = NoAssignmentInExpressionsConfiguration()
43+
config.multiElementCollectionTrailingCommas = true
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return config
4445
}
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}

‎Tests/SwiftFormatTests/PrettyPrint/CommaTests.swift

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,289 @@
1+
import SwiftFormat
2+
3+
final class CommaTests: PrettyPrintTestCase {
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func testArrayCommasAbsentEnabled() {
5+
let input =
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"""
7+
let MyCollection = [
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1,
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2,
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3
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]
12+
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"""
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let expected =
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"""
17+
let MyCollection = [
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1,
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2,
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3,
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]
22+
23+
"""
24+
25+
var configuration = Configuration.forTesting
26+
configuration.multiElementCollectionTrailingCommas = true
27+
assertPrettyPrintEqual(input: input, expected: expected, linelength: 20, configuration: configuration)
28+
}
29+
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func testArrayCommasAbsentDisabled() {
31+
let input =
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"""
33+
let MyCollection = [
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1,
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2,
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3
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]
38+
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"""
40+
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let expected =
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"""
43+
let MyCollection = [
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1,
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2,
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3
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]
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"""
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var configuration = Configuration.forTesting
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configuration.multiElementCollectionTrailingCommas = false
53+
assertPrettyPrintEqual(input: input, expected: expected, linelength: 20, configuration: configuration)
54+
}
55+
56+
func testArrayCommasPresentEnabled() {
57+
let input =
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"""
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let MyCollection = [
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1,
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2,
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3,
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]
64+
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"""
66+
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let expected =
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"""
69+
let MyCollection = [
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1,
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2,
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3,
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]
74+
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"""
76+
77+
var configuration = Configuration.forTesting
78+
configuration.multiElementCollectionTrailingCommas = true
79+
assertPrettyPrintEqual(input: input, expected: expected, linelength: 20, configuration: configuration)
80+
}
81+
82+
func testArrayCommasPresentDisabled() {
83+
let input =
84+
"""
85+
let MyCollection = [
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1,
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2,
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3,
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]
90+
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"""
92+
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let expected =
94+
"""
95+
let MyCollection = [
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1,
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2,
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3
99+
]
100+
101+
"""
102+
103+
var configuration = Configuration.forTesting
104+
configuration.multiElementCollectionTrailingCommas = false
105+
assertPrettyPrintEqual(input: input, expected: expected, linelength: 20, configuration: configuration)
106+
}
107+
108+
func testArraySingleLineCommasPresentDisabled() {
109+
let input =
110+
"""
111+
let MyCollection = [1, 2, 3,]
112+
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"""
114+
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// no effect expected
116+
let expected =
117+
"""
118+
let MyCollection = [1, 2, 3]
119+
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"""
121+
122+
var configuration = Configuration.forTesting
123+
configuration.multiElementCollectionTrailingCommas = true
124+
assertPrettyPrintEqual(input: input, expected: expected, linelength: 40, configuration: configuration)
125+
}
126+
127+
func testArraySingleLineCommasPresentEnabled() {
128+
let input =
129+
"""
130+
let MyCollection = [1, 2, 3,]
131+
132+
"""
133+
134+
// no effect expected
135+
let expected =
136+
"""
137+
let MyCollection = [1, 2, 3]
138+
139+
"""
140+
141+
var configuration = Configuration.forTesting
142+
configuration.multiElementCollectionTrailingCommas = false
143+
assertPrettyPrintEqual(input: input, expected: expected, linelength: 40, configuration: configuration)
144+
}
145+
146+
func testDictionaryCommasAbsentEnabled() {
147+
let input =
148+
"""
149+
let MyCollection = [
150+
"a": 1,
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"b": 2,
152+
"c": 3
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]
154+
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"""
156+
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let expected =
158+
"""
159+
let MyCollection = [
160+
"a": 1,
161+
"b": 2,
162+
"c": 3,
163+
]
164+
165+
"""
166+
167+
var configuration = Configuration.forTesting
168+
configuration.multiElementCollectionTrailingCommas = true
169+
assertPrettyPrintEqual(input: input, expected: expected, linelength: 20, configuration: configuration)
170+
}
171+
172+
func testDictionaryCommasAbsentDisabled() {
173+
let input =
174+
"""
175+
let MyCollection = [
176+
"a": 1,
177+
"b": 2,
178+
"c": 3
179+
]
180+
181+
"""
182+
183+
let expected =
184+
"""
185+
let MyCollection = [
186+
"a": 1,
187+
"b": 2,
188+
"c": 3
189+
]
190+
191+
"""
192+
193+
var configuration = Configuration.forTesting
194+
configuration.multiElementCollectionTrailingCommas = false
195+
assertPrettyPrintEqual(input: input, expected: expected, linelength: 20, configuration: configuration)
196+
}
197+
198+
func testDictionaryCommasPresentEnabled() {
199+
let input =
200+
"""
201+
let MyCollection = [
202+
"a": 1,
203+
"b": 2,
204+
"c": 3,
205+
]
206+
207+
"""
208+
209+
let expected =
210+
"""
211+
let MyCollection = [
212+
"a": 1,
213+
"b": 2,
214+
"c": 3,
215+
]
216+
217+
"""
218+
219+
var configuration = Configuration.forTesting
220+
configuration.multiElementCollectionTrailingCommas = true
221+
assertPrettyPrintEqual(input: input, expected: expected, linelength: 20, configuration: configuration)
222+
}
223+
224+
func testDictionaryCommasPresentDisabled() {
225+
let input =
226+
"""
227+
let MyCollection = [
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"a": 1,
229+
"b": 2,
230+
"c": 3,
231+
]
232+
233+
"""
234+
235+
let expected =
236+
"""
237+
let MyCollection = [
238+
"a": 1,
239+
"b": 2,
240+
"c": 3
241+
]
242+
243+
"""
244+
245+
var configuration = Configuration.forTesting
246+
configuration.multiElementCollectionTrailingCommas = false
247+
assertPrettyPrintEqual(input: input, expected: expected, linelength: 20, configuration: configuration)
248+
}
249+
250+
func testDictionarySingleLineCommasPresentDisabled() {
251+
let input =
252+
"""
253+
let MyCollection = ["a": 1, "b": 2, "c": 3,]
254+
255+
"""
256+
257+
let expected =
258+
"""
259+
let MyCollection = [
260+
"a": 1, "b": 2, "c": 3,
261+
]
262+
263+
"""
264+
265+
var configuration = Configuration.forTesting
266+
configuration.multiElementCollectionTrailingCommas = true
267+
assertPrettyPrintEqual(input: input, expected: expected, linelength: 40, configuration: configuration)
268+
}
269+
270+
func testDictionarySingleLineCommasPresentEnabled() {
271+
let input =
272+
"""
273+
let MyCollection = ["a": 1, "b": 2, "c": 3,]
274+
275+
"""
276+
277+
let expected =
278+
"""
279+
let MyCollection = [
280+
"a": 1, "b": 2, "c": 3
281+
]
282+
283+
"""
284+
285+
var configuration = Configuration.forTesting
286+
configuration.multiElementCollectionTrailingCommas = false
287+
assertPrettyPrintEqual(input: input, expected: expected, linelength: 40, configuration: configuration)
288+
}
289+
}

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