Request: Line break for each multiline chain expression

[valentin-mille]

Is it plan to add line break for each multiline chain expression? It may be really helpful for SwiftUI view modifiers. For example with :

👉 The input view I want to format

import SwiftUI

struct OkFormattedView: View {
	
	var body: some View {
		VStack {
			Text("Hello, world!" )
		}.padding().background(.red).frame(maxWidth: .infinity, maxHeight: .infinity)
	}
}

❌ The result with the .swift-format configuration file (see below)

import SwiftUI

struct OkFormattedView: View {

	var body: some View {
		VStack {
			Text("Hello, world!")
		}
		.padding().background(.red).frame(maxWidth: .infinity, maxHeight: .infinity)
	}
}

✅ The expected result with the feature request

import SwiftUI

struct OkFormattedView: View {

	var body: some View {
		VStack {
			Text("Hello, world!")
		}
		.padding()
		.background(.red)
		.frame(maxWidth: .infinity, maxHeight: .infinity)
	}
}

.swift-format config used

{
  "version" : 1,
  "lineLength" : 120,
  "indentation" : {
    "tabs" : 1
  },
  "tabWidth" : 4,
  "maximumBlankLines" : 1,
  "respectsExistingLineBreaks" : true,
  "lineBreakBeforeControlFlowKeywords" : false,
  "lineBreakBeforeEachArgument" : true,
  "lineBreakBeforeEachGenericRequirement" : false,
  "prioritizeKeepingFunctionOutputTogether" : false,
  "indentConditionalCompilationBlocks" : false,
  "lineBreakAroundMultilineExpressionChainComponents" : true,
  "fileScopedDeclarationPrivacy" : {
    "accessLevel" : "private"
  },
  "indentSwitchCaseLabels" : false,
  "rules" : {
    "AllPublicDeclarationsHaveDocumentation" : false,
    "AlwaysUseLowerCamelCase" : true,
    "AmbiguousTrailingClosureOverload" : true,
    "BeginDocumentationCommentWithOneLineSummary" : false,
    "DoNotUseSemicolons" : true,
    "DontRepeatTypeInStaticProperties" : true,
    "FileScopedDeclarationPrivacy" : true,
    "FullyIndirectEnum" : true,
    "GroupNumericLiterals" : true,
    "IdentifiersMustBeASCII" : true,
    "NeverForceUnwrap" : false,
    "NeverUseForceTry" : false,
    "NeverUseImplicitlyUnwrappedOptionals" : false,
    "NoAccessLevelOnExtensionDeclaration" : false,
    "NoAssignmentInExpressions" : true,
    "NoBlockComments" : true,
    "NoCasesWithOnlyFallthrough" : true,
    "NoEmptyTrailingClosureParentheses" : true,
    "NoLabelsInCasePatterns" : true,
    "NoLeadingUnderscores" : false,
    "NoParensAroundConditions" : true,
    "NoVoidReturnOnFunctionSignature" : true,
    "OneCasePerLine" : true,
    "OneVariableDeclarationPerLine" : true,
    "OnlyOneTrailingClosureArgument" : true,
    "OrderedImports" : true,
    "ReturnVoidInsteadOfEmptyTuple" : true,
    "UseEarlyExits" : false,
    "UseLetInEveryBoundCaseVariable" : true,
    "UseShorthandTypeNames" : true,
    "UseSingleLinePropertyGetter" : true,
    "UseSynthesizedInitializer" : true,
    "UseTripleSlashForDocumentationComments" : true,
    "UseWhereClausesInForLoops" : false,
    "ValidateDocumentationComments" : false
  },
  "spacesAroundRangeFormationOperators" : false,
}

[allevato]

This sounds like an interesting idea. I don't think we'd want it in member chains in general (e.g., a.b.c.d), and I don't want to try to detect things like "this is a SwiftUI context", but maybe we could say that if the chain contains function calls, we always break after each function call?

[allevato]

Actually, can you try setting lineBreakAroundMultilineExpressionChainComponents in your configuration and see if that works for you?

[valentin-mille]

I agree with your point @allevato. We don't need to analyze the context to know if we are in SwiftUI or UIKit. Applying it to every chain function call may be relevant, even in Swift (e.g. Combine code could be an excellent example with chained subscribers).

In my previous message, lineBreakAroundMultilineExpressionChainComponents was set to true and just broke the line of the first chaining expression. Setting it to false doesn't format the chain expression. It may be better to break each multiline expression when the option is true or create another option for that specific case (to not change existing configuration behavior). Please refer to my previous message for more details about the configuration and the results.

[kuglee]

This would be great to have.

[HassanTaleb90]

Interesting

[ahoppen]

Tracked in Apple’s issue tracker as rdar://126948253