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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
import SwiftSyntax
private let utf8Newline = UTF8.CodeUnit(ascii: "\n")
private let utf8Tab = UTF8.CodeUnit(ascii: "\t")
/// Emits linter errors for whitespace style violations by comparing the raw text of the input Swift
/// code with formatted text.
@_spi(Testing)
public class WhitespaceLinter {
/// The text of the input source code to be linted.
private let userText: [UTF8.CodeUnit]
/// The formatted version of `userText`.
private let formattedText: [UTF8.CodeUnit]
/// The Context object containing the DiagnosticEngine.
private let context: Context
/// Is the current line too long?
private var isLineTooLong: Bool
/// Creates a new WhitespaceLinter with the given context.
///
/// - Parameters:
/// - user: The text of the Swift source code to be linted.
/// - formatted: The formatted text to compare to `user`.
/// - context: The context object containing the DiagnosticEngine instance we wish to use.
public init(user: String, formatted: String, context: Context) {
self.userText = Array(user.utf8)
self.formattedText = Array(formatted.utf8)
self.context = context
self.isLineTooLong = false
}
/// Perform whitespace linting.
public func lint() {
var userIndex = 0
var formattedIndex = 0
var userWhitespace: ArraySlice<UTF8.CodeUnit>
repeat {
userWhitespace = contiguousWhitespace(startingAt: userIndex, in: userText)
let formattedWhitespace = contiguousWhitespace(startingAt: formattedIndex, in: formattedText)
// `userText` and `formattedText` should only differ in their whitespace characters.
assert(
safeCodeUnit(at: userWhitespace.endIndex, in: userText)
== safeCodeUnit(at: formattedWhitespace.endIndex, in: formattedText),
"Non-whitespace characters do not match")
compareWhitespace(userWhitespace: userWhitespace, formattedWhitespace: formattedWhitespace)
userIndex = userWhitespace.endIndex + 1
formattedIndex = formattedWhitespace.endIndex + 1
} while userWhitespace.endIndex != userText.endIndex
}
/// Compare the whitespace buffers between the user text and formatted text, and emit linter
/// errors accordingly.
///
/// Note: properly formatted whitespace will always be some number of newline characters
/// followed by some number of spaces in the absence of trailing whitespace (which the
/// pretty-printer ensures). e.g. "\n ", "\n\n ", "\n", " ". The user's whitespace could have
/// spaces and newlines in any order. e.g. " \n ", " \n", etc.
///
/// - Parameters:
/// - userWhitespace: A slice of user text representing the current span of contiguous
/// whitespace.
/// - formattedWhitespace: A slice of formatted text representing the current span of contiguous
/// whitespace that will be compared to the user whitespace.
private func compareWhitespace(
userWhitespace: ArraySlice<UTF8.CodeUnit>, formattedWhitespace: ArraySlice<UTF8.CodeUnit>
) {
// We use a custom-crafted lazy-splitting iterator here instead of the standard
// `Collection.split` function because Time Profiler indicated that a very large proportion of
// the runtime of this function was spent allocating arrays inside `split` and then subsequently
// deallocating those arrays. For the sizes of whitespace runs we're likely to work with, it is
// much faster to pre-scan to count the number of runs and then do a single pass again over the
// whitespace without allocating any intermediate storage.
let userRuns = userWhitespace.lazilySplit(separator: utf8Newline)
let formattedRuns = formattedWhitespace.lazilySplit(separator: utf8Newline)
checkForLineLengthErrors(
userIndex: userWhitespace.startIndex,
formattedIndex: formattedWhitespace.startIndex,
userRuns: userRuns,
formattedRuns: formattedRuns)
// No need to perform any further checks if the whitespace is identical.
guard userWhitespace != formattedWhitespace else { return }
var userIndex = userWhitespace.startIndex
var userRunsIterator = RememberingIterator(userRuns.makeIterator())
var formattedRunsIterator = RememberingIterator(formattedRuns.makeIterator())
if userRuns.count == 1 && formattedRuns.count == 1 {
let userRun = userRunsIterator.next()!
let formattedRun = formattedRunsIterator.next()!
// If there was only a single whitespace run in each input, then that means there weren't any
// newlines. Therefore, we're looking at inter-token spacing, unless the whitespace runs
// preceded the first token in the file (i.e., offset == 0), in which case we ignore it here
// and handle it as an indentation check below.
if userIndex > 0 {
checkForSpacingErrors(userIndex: userIndex, userRun: userRun, formattedRun: formattedRun)
}
} else {
var runIndex = 0
let excessUserLines = userRuns.count - formattedRuns.count
while let userRun = userRunsIterator.next() {
let possibleFormattedRun = formattedRunsIterator.next()
if runIndex < excessUserLines {
// If there were excess newlines in the user input, tell the user to remove them. This
// short-circuits the trailing whitespace check below; we don't bother telling the user
// about trailing whitespace on a line that we're also telling them to delete.
diagnose(.removeLineError, category: .removeLine, utf8Offset: userIndex)
userIndex += userRun.count + 1
} else if runIndex != userRuns.count - 1 {
if let formattedRun = possibleFormattedRun {
// If this isn't the last whitespace run, then it must precede a newline, so we check
// for trailing whitespace violations.
checkForTrailingWhitespaceErrors(
userIndex: userIndex, userRun: userRun, formattedRun: formattedRun)
}
userIndex += userRun.count + 1
}
runIndex += 1
}
}
if userIndex == 0 || (userRuns.count > 1 && formattedRuns.count > 1) {
// Advance to the last formatted whitespace run if we haven't already. This run precedes
// a token, so we check it for leading indentation violations.
while formattedRunsIterator.next() != nil {}
if let lastFormattedRun = formattedRunsIterator.latestElement {
checkForIndentationErrors(
userIndex: userIndex,
userRun: userRunsIterator.latestElement!,
formattedRun: lastFormattedRun)
}
}
// If there were more lines in the formatted output and the user's line did not exceed the
// line length limit, tell the user to add the necessary blank lines.
let excessFormattedLines = formattedRuns.count - userRuns.count
if excessFormattedLines > 0 && !isLineTooLong {
diagnose(
.addLinesError(excessFormattedLines),
category: .addLines,
utf8Offset: userWhitespace.startIndex)
}
}
/// Check the user text for line length violations.
///
/// - Parameters:
/// - userIndex The current character offset within the user text.
/// - formattedIndex: The current character offset within the formatted text.
/// - userRuns: The current newline-separated runs of whitespace in the user text.
/// - formattedRuns: The current newline-separated runs of whitespace in the formatted text.
private func checkForLineLengthErrors(
userIndex: Int,
formattedIndex: Int,
userRuns: LazySplitSequence<ArraySlice<UTF8.CodeUnit>>,
formattedRuns: LazySplitSequence<ArraySlice<UTF8.CodeUnit>>
) {
// Only run this check at the start of a line.
guard
(userRuns.count > 1 && formattedRuns.count > 1)
|| (userRuns.count == 1 && formattedRuns.count == 1 && userIndex == 0)
else {
return
}
let lengthLimit = context.configuration.lineLength
// Move the offset to the first non-whitespace character.
var adjustedUserIndex = userIndex
var lastUserRun: ArraySlice<UTF8.CodeUnit>!
for (index, userRun) in userRuns.enumerated() {
lastUserRun = userRun
if index < userRuns.count - 1 {
adjustedUserIndex += userRun.count + 1
}
}
// Calculate the length of the user's line.
let userIndent = lastUserRun.count
var userLength = userIndent
for index in adjustedUserIndex..<userText.count {
// Count characters up to the newline.
if userText[index] == utf8Newline { break }
userLength += 1
}
// Exit if the user's line is within limits
if userLength <= lengthLimit {
isLineTooLong = false
return
}
// Move the offset to the first non-whitespace character.
var adjustedFormattedIndex = formattedIndex
var lastFormattedRun: ArraySlice<UTF8.CodeUnit>!
for (index, formattedRun) in formattedRuns.enumerated() {
lastFormattedRun = formattedRun
if index < formattedRuns.count - 1 {
adjustedFormattedIndex += formattedRun.count + 1
}
}
// Calculate the length of the formatted line.
let formattedIndent = lastFormattedRun.count
var formattedLength = formattedIndent
for index in adjustedFormattedIndex..<formattedText.count {
// Count characters up to the newline.
if formattedText[index] == utf8Newline { break }
formattedLength += 1
}
// If the formatted text produces a line that is too long, don't raise an error.
if formattedLength > lengthLimit {
isLineTooLong = false
return
}
isLineTooLong = true
diagnose(.lineLengthError, category: .lineLength, utf8Offset: adjustedUserIndex)
}
/// Compare user and formatted whitespace buffers, and check for indentation errors.
///
/// Example:
///
/// func myFun() {
/// let a = 123 // Indentation error on this line
/// }
///
/// - Parameters:
/// - userIndex: The current character offset within the user text.
/// - userRun: A run of whitespace from the user text.
/// - formattedRun: A run of whitespace from the formatted text.
private func checkForIndentationErrors(
userIndex: Int, userRun: ArraySlice<UTF8.CodeUnit>, formattedRun: ArraySlice<UTF8.CodeUnit>
) {
guard userRun != formattedRun else { return }
let actual = indentation(of: userRun)
let expected = indentation(of: formattedRun)
diagnose(
.indentationError(expected: expected, actual: actual),
category: .indentation,
utf8Offset: userIndex)
}
/// Compare user and formatted whitespace buffers, and check for trailing whitespace.
///
/// - Parameters:
/// - userIndex: The current character offset within the user text.
/// - userRun: The tokenized user whitespace buffer.
/// - formattedRun: The tokenized formatted whitespace buffer.
private func checkForTrailingWhitespaceErrors(
userIndex: Int, userRun: ArraySlice<UTF8.CodeUnit>, formattedRun: ArraySlice<UTF8.CodeUnit>
) {
if userRun != formattedRun {
diagnose(.trailingWhitespaceError, category: .trailingWhitespace, utf8Offset: userIndex)
}
}
/// Compare user and formatted whitespace buffers, and check for spacing errors.
///
/// Example:
///
/// let a : Int = 123 // Spacing error before the colon
///
/// - Parameters:
/// - userIndex: The current character offset within the user text.
/// - userRun: The tokenized user whitespace buffer.
/// - formattedRun: The tokenized formatted whitespace buffer.
private func checkForSpacingErrors(
userIndex: Int, userRun: ArraySlice<UTF8.CodeUnit>, formattedRun: ArraySlice<UTF8.CodeUnit>
) {
guard userRun != formattedRun else { return }
// This assumes tabs will always be forbidden for inter-token spacing (but not for leading
// indentation).
if userRun.contains(utf8Tab) {
diagnose(.spacingCharError, category: .spacingCharacter, utf8Offset: userIndex)
} else if formattedRun.count != userRun.count {
let delta = formattedRun.count - userRun.count
diagnose(.spacingError(delta), category: .spacing, utf8Offset: userIndex)
}
}
/// Find the next non-whitespace character in a given string, and any leading whitespace before
/// the character.
///
/// If the character at `offset` is whitespace, we scan forward until we find a non-whitespace
/// character. We then return the new offset, the character we landed on, and a string containing
/// the character's leading whitespace.
///
/// - Parameters:
/// - offset: The printable character offset within the string.
/// - data: The input string.
/// - Returns: A slice of `data` that covers the contiguous whitespace starting at the given
/// index.
private func contiguousWhitespace(startingAt offset: Int, in data: [UTF8.CodeUnit])
-> ArraySlice<UTF8.CodeUnit>
{
guard let whitespaceEnd =
data[offset...].firstIndex(where: { !UnicodeScalar($0).properties.isWhitespace })
else {
return data[offset..<data.endIndex]
}
return data[offset..<whitespaceEnd]
}
/// Returns the code unit at the given index, or nil if the index is the end of the data.
///
/// This helper is only used in an assertion that verifies that the non-whitespace code units in
/// the text are identical, but is not evaluated in release builds.
private func safeCodeUnit(at index: Int, in data: [UTF8.CodeUnit]) -> UTF8.CodeUnit? {
return index != data.endIndex ? data[index] : nil
}
/// Emits a finding with the given message and category. The message will correspond to a specific
/// location (line and column number) in the input Swift source file (`userText`).
///
/// - Parameters:
/// - message: The message we wish to emit.
/// - category: The category of the finding.
/// - utf8Offset: The UTF-8 offset location of the message.
private func diagnose(
_ message: Finding.Message,
category: WhitespaceFindingCategory,
utf8Offset: Int
) {
let absolutePosition = AbsolutePosition(utf8Offset: utf8Offset)
let sourceLocation = context.sourceLocationConverter.location(for: absolutePosition)
context.findingEmitter.emit(
message, category: category, location: Finding.Location(sourceLocation))
}
/// Returns the indentation that represents the indentation of the given whitespace, which is the
/// leading spacing for a line.
private func indentation(of whitespace: ArraySlice<UTF8.CodeUnit>) -> WhitespaceIndentation {
if whitespace.count == 0 {
return .none
}
var orderedRuns: [(char: UTF8.CodeUnit, count: Int)] = []
for char in whitespace {
let lastRun = orderedRuns.last
if lastRun?.char == char {
orderedRuns[orderedRuns.endIndex - 1].count += 1
} else {
orderedRuns.append((char, 1))
}
}
let indents = orderedRuns.map { run in
// Assumes any non-tab whitespace character is some type of space.
return run.char == utf8Tab ? Indent.tabs(run.count) : Indent.spaces(run.count)
}
if indents.count == 1, let onlyIndent = indents.first {
return .homogeneous(onlyIndent)
}
return .heterogeneous(indents)
}
}
/// Describes the composition of the whitespace that creates an indentation for a line of code.
public enum WhitespaceIndentation: Equatable {
/// The line has no preceding whitespace, meaning there's no indentation.
case none
/// The line's leading whitespace consists of a single run of one kind of whitespace character.
case homogeneous(Indent)
/// The line's leading whitespace consists of multiple runs of different kinds of whitespace
/// characters.
case heterogeneous([Indent])
}
extension Indent {
/// Returns a string that describes the indentation in a human readable format, which is
/// appropriate for use in diagnostic messages.
fileprivate var diagnosticDescription: String {
switch self {
case .spaces(let count):
let noun = count == 1 ? "space" : "spaces"
return "\(count) \(noun)"
case .tabs(let count):
let noun = count == 1 ? "tab" : "tabs"
return "\(count) \(noun)"
}
}
}
extension WhitespaceIndentation {
/// Returns a string that describes the whitespace in a human readable format, which is
/// appropriate for use in diagnostic messages.
fileprivate var diagnosticDescription: String {
switch self {
case .none:
return "no indentation"
case .heterogeneous(let indents):
guard let first = indents.first else { return "no indentation" }
return indents.dropFirst().reduce(first.diagnosticDescription) {
return $0 + ", " + $1.diagnosticDescription
}
case .homogeneous(let indent):
return indent.diagnosticDescription
}
}
}
extension Finding.Message {
fileprivate static let trailingWhitespaceError: Finding.Message = "remove trailing whitespace"
fileprivate static func indentationError(
expected expectedIndentation: WhitespaceIndentation,
actual actualIndentation: WhitespaceIndentation
) -> Finding.Message {
switch expectedIndentation {
case .none:
return "remove all leading whitespace"
case .homogeneous, .heterogeneous:
if case .homogeneous(let expectedIndent) = expectedIndentation,
case .homogeneous(let actualIndent) = actualIndentation
{
if case .spaces(let expectedCount) = expectedIndent,
case .spaces(let actualCount) = actualIndent
{
let delta = expectedCount - actualCount
let verb = delta > 0 ? "indent" : "unindent"
return "\(verb) by \(abs(delta)) spaces"
}
if case .tabs(let expectedCount) = expectedIndent,
case .tabs(let actualCount) = actualIndent
{
let delta = expectedCount - actualCount
let verb = delta > 0 ? "indent" : "unindent"
return "\(verb) by \(abs(delta)) tabs"
}
// Intentionally fallthrough to the heterogeneous indentation diagnostic below.
}
// Otherwise, the change can't be described by a simple add/remove N spaces/tabs. It's easier
// to instruct the user to remove the existing whitespace and add the appropriate sequence of
// indenting characters.
let expectedDescription = expectedIndentation.diagnosticDescription
return "replace leading whitespace with \(expectedDescription)"
}
}
fileprivate static func spacingError(_ spaces: Int) -> Finding.Message {
let verb = spaces > 0 ? "add" : "remove"
let noun = abs(spaces) == 1 ? "space" : "spaces"
return "\(verb) \(abs(spaces)) \(noun)"
}
fileprivate static let spacingCharError: Finding.Message = "use spaces for spacing"
fileprivate static let removeLineError: Finding.Message = "remove line break"
fileprivate static func addLinesError(_ lines: Int) -> Finding.Message {
let noun = lines == 1 ? "break" : "breaks"
return "add \(lines) line \(noun)"
}
fileprivate static let lineLengthError: Finding.Message = "line is too long"
}
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