Unexpected Multiline Arguments Violation in function call with completion block

[DamascenoRafael]

New Issue Checklist

• Updated SwiftLint to the latest version
• I searched for existing GitHub issues

Describe the bug

It seems that in a specific case of a function call with a completion block where the function's arguments are one per line, a violation is triggered if the final parentheses of the arguments are on the same line.

// This triggers a violation:
// Multiline Arguments Violation: Arguments should be either on the same line, or one per line. (multiline_arguments)
UIView.animate(withDuration: 1,
               delay: 0) {
    // sample
    print("a")
} completion: { _ in
    // sample
    print("b")
}

Sorry if I'm missing something. I looked at the rules for Multiline Arguments and looked for issues but it seems to me that my example that triggers the violation should not occur.

Complete output when running SwiftLint, including the stack trace and command used

$ swiftlint lint
Loading configuration from '.swiftlint.yml'
Linting Swift files at paths 
...
/path/file.swift:527:76: warning: Multiline Arguments Violation: Arguments should be either on the same line, or one per line. (multiline_arguments)
Done linting! Found 2 violations, 0 serious in 29 files.

Environment

• SwiftLint version 0.40.3
• Installation method used: Homebrew
• Paste your configuration file:

opt_in_rules:
- attributes
- closure_end_indentation
- closure_spacing
- contains_over_first_not_nil
- empty_count
- empty_string
- explicit_init
- fallthrough
- file_header
- first_where
- force_unwrapping
- implicit_return
- implicitly_unwrapped_optional
- joined_default_parameter
- missing_docs
- multiline_arguments
- multiline_function_chains
- multiline_parameters
- operator_usage_whitespace
- overridden_super_call
- redundant_nil_coalescing
- redundant_type_annotation
- sorted_first_last
- switch_case_on_newline
- toggle_bool
- unneeded_parentheses_in_closure_argument
- vertical_whitespace_closing_braces
- yoda_condition

disabled_rules:
- trailing_whitespace

attributes:
  always_on_same_line:
  - '@objc'
  - '@IBAction'

implicit_return:
  included:
  - closure

line_length:
  error: 300
  ignores_urls: true

multiline_arguments:
  only_enforce_after_first_closure_on_first_line: true

custom_rules:
  comments_space:
    name: "Space After Comment"
    regex: '(^ *//\w+)'
    message: "There should be a space after //"
    severity: warning
  double_space:
    include: "*.swift"
    name: "Double space"
    regex: '([a-z,A-Z] \s+)'
    message: "Don't use double space between keywords"
    match_kinds: keyword
    severity: warning
  empty_commented_line:
    name: "Empty Commented Out Line"
    regex: '(\t+| +)//\n'
    message: "Remove useless comment lines or use /* format */"
    severity: warning
  missing_closure_name:
    name: "Missing closure name"
    regex: '^\s*\}\) \{.*'
    message: "Add the missing closure name"
    severity: warning

• Are you using nested configurations? No
• Which Xcode version are you using? Xcode 12.1 Build version 12A7403

example that trigger a violation:

// This triggers a violation:
// Multiline Arguments Violation: Arguments should be either on the same line, or one per line. (multiline_arguments)
UIView.animate(withDuration: 1,
               delay: 0) {
    // sample
    print("a")
} completion: { _ in
    // sample
    print("b")
}

examples that do not trigger a violation:

// The violation is not triggered.
UIView.animate(withDuration: 1,
               delay: 0
) {
    // sample
    print("a")
} completion: { _ in
    // sample
    print("b")
}

// The violation is not triggered.
UIView.animate(withDuration: 1,
               delay: 0) {
    // sample
    print("a")
}

[stale]

This issue has been automatically marked as stale because it has not had any recent activity. Please comment to prevent this issue from being closed. Thank you for your contributions!

[DamascenoRafael]

It is still a bug in version 0.42.0

[Jeehut]

Just ran into this, too with the following SwiftUI code:

Picker(selection: viewStore.binding(\.$someProperty)) {
   ForEach(SomeEnum.allCases, id: \.rawValue) { someCase in
      Text(someCase.rawValue)
         .tag(someCase)
   }
} label: {
   EmptyView()
}

[417-72KI]

It is still a bug in version 0.49.1

[drspoton]

Still a but in 0.50.1

[rberggreen]

Still a bug in version 0.50.3. I always get some false positive warning when using multiple trailing closures along with other parameters, regardless of whether I place those other parameters on multiple lines.

TestView(
    param1: "something",
    param2: 0
) { // Vertical Parameter Alignment On Call Violation
    Text("Some view 1")
} closure2: {
    Text("Some view 2")
}

TestView(param1: "something", param2: 0) { // Multiline Arguments Violation
    Text("Some view 1")
} closure2: {
    Text("Some view 2")
}

No warnings:

TestView {
    Text("Some view 1")
} closure2: {
    Text("Some view 2")
}