.swift-format: Specify an exhaustive configuration

[AnthonyLatsis]

Mirrors swiftlang/swift-syntax#3117.

---

Unexpectedly, an omitted rule tells swift-format to ignore it altogether rather than assume the default setting.

This change applies the default configuration, retaining current settings and disabling 3 default-enabled rules: DoNotUseSemicolons, NoAccessLevelOnExtensionDeclaration, and DontRepeatTypeInStaticProperties. The latter is disabled due to undesired effect:

warning: [DontRepeatTypeInStaticProperties] remove the suffix 'Paths' from the name of the variable 'envSearchPaths'

[allevato]

The configuration decoder explicitly uses decodeIfPresent and falls back to the default values if the key wasn't in the JSON:

swift-format/Sources/SwiftFormat/API/Configuration.swift

Lines 317 to 432 in 2a1d811

	// Unfortunately, to allow the user to leave out configuration options in the JSON, we would
	// have to make them optional properties, but that makes using the type in the rest of the code
	// more annoying because we'd have to unwrap everything. So, we override this initializer and
	// provide the defaults ourselves if needed. We get those defaults by pulling them from a
	// default-initialized instance.
	let defaults = Configuration()
	self.maximumBlankLines =
	try container.decodeIfPresent(Int.self, forKey: .maximumBlankLines)
	?? defaults.maximumBlankLines
	self.lineLength =
	try container.decodeIfPresent(Int.self, forKey: .lineLength)
	?? defaults.lineLength
	self.spacesBeforeEndOfLineComments =
	try container.decodeIfPresent(Int.self, forKey: .spacesBeforeEndOfLineComments)
	?? defaults.spacesBeforeEndOfLineComments
	self.tabWidth =
	try container.decodeIfPresent(Int.self, forKey: .tabWidth)
	?? defaults.tabWidth
	self.indentation =
	try container.decodeIfPresent(Indent.self, forKey: .indentation)
	?? defaults.indentation
	self.respectsExistingLineBreaks =
	try container.decodeIfPresent(Bool.self, forKey: .respectsExistingLineBreaks)
	?? defaults.respectsExistingLineBreaks
	self.lineBreakBeforeControlFlowKeywords =
	try container.decodeIfPresent(Bool.self, forKey: .lineBreakBeforeControlFlowKeywords)
	?? defaults.lineBreakBeforeControlFlowKeywords
	self.lineBreakBeforeEachArgument =
	try container.decodeIfPresent(Bool.self, forKey: .lineBreakBeforeEachArgument)
	?? defaults.lineBreakBeforeEachArgument
	self.lineBreakBeforeEachGenericRequirement =
	try container.decodeIfPresent(Bool.self, forKey: .lineBreakBeforeEachGenericRequirement)
	?? defaults.lineBreakBeforeEachGenericRequirement
	self.lineBreakBetweenDeclarationAttributes =
	try container.decodeIfPresent(Bool.self, forKey: .lineBreakBetweenDeclarationAttributes)
	?? defaults.lineBreakBetweenDeclarationAttributes
	self.prioritizeKeepingFunctionOutputTogether =
	try container.decodeIfPresent(Bool.self, forKey: .prioritizeKeepingFunctionOutputTogether)
	?? defaults.prioritizeKeepingFunctionOutputTogether
	self.indentConditionalCompilationBlocks =
	try container.decodeIfPresent(Bool.self, forKey: .indentConditionalCompilationBlocks)
	?? defaults.indentConditionalCompilationBlocks
	self.lineBreakAroundMultilineExpressionChainComponents =
	try container.decodeIfPresent(
	Bool.self,
	forKey: .lineBreakAroundMultilineExpressionChainComponents
	)
	?? defaults.lineBreakAroundMultilineExpressionChainComponents
	self.spacesAroundRangeFormationOperators =
	try container.decodeIfPresent(
	Bool.self,
	forKey: .spacesAroundRangeFormationOperators
	)
	?? defaults.spacesAroundRangeFormationOperators
	self.fileScopedDeclarationPrivacy =
	try container.decodeIfPresent(
	FileScopedDeclarationPrivacyConfiguration.self,
	forKey: .fileScopedDeclarationPrivacy
	)
	?? defaults.fileScopedDeclarationPrivacy
	self.indentSwitchCaseLabels =
	try container.decodeIfPresent(Bool.self, forKey: .indentSwitchCaseLabels)
	?? defaults.indentSwitchCaseLabels
	self.noAssignmentInExpressions =
	try container.decodeIfPresent(
	NoAssignmentInExpressionsConfiguration.self,
	forKey: .noAssignmentInExpressions
	)
	?? defaults.noAssignmentInExpressions
	self.multiElementCollectionTrailingCommas =
	try container.decodeIfPresent(
	Bool.self,
	forKey: .multiElementCollectionTrailingCommas
	)
	?? defaults.multiElementCollectionTrailingCommas
	self.reflowMultilineStringLiterals = try {
	// Try to decode `reflowMultilineStringLiterals` as a string
	// This handles configurations using the String raw value format (e.g. "never").
	// If an error occurs, we'll silently bypass it and fall back to the legacy behavior.
	if let behavior = try? container.decodeIfPresent(
	MultilineStringReflowBehavior.self,
	forKey: .reflowMultilineStringLiterals
	) {
	return behavior
	}
	// If the modern format fails, try to decode as an object with a single key.
	// This handles configurations from swift-format v601.0.0 (e.g. { "never": {} }).
	// If an error occurs in this step, we'll propagate it to the caller.
	if let legacyBehavior = try container.decodeIfPresent(
	LegacyMultilineStringReflowBehavior.self,
	forKey: .reflowMultilineStringLiterals
	) {
	return legacyBehavior.toMultilineStringReflowBehavior()
	}
	// If the key is not present in the configuration at all, use the default value.
	return defaults.reflowMultilineStringLiterals
	}()
	self.indentBlankLines =
	try container.decodeIfPresent(
	Bool.self,
	forKey: .indentBlankLines
	)
	?? defaults.indentBlankLines
	// If the `rules` key is not present at all, default it to the built-in set
	// so that the behavior is the same as if the configuration had been
	// default-initialized. To get an empty rules dictionary, one can explicitly
	// set the `rules` key to `{}`.
	self.rules =
	try container.decodeIfPresent([String: Bool].self, forKey: .rules)
	?? defaults.rules

...ah, but that still means that any rules dictionary being present will be used as the entire thing, rather than assuming the default values for any rules not present. We should probably fix that.

In the meantime, no reason to block this PR on that fix.

[bnbarham]

We should probably fix that.

Indeed. Though it's probably something we need to do under a new "style" given how breaking it could be 😓