Added StringFilters.camelToSnakeCase filter

CHANGELOG.md

@@ -16,7 +16,9 @@ _None_
 
 ### New Features
 
-_None_
+* Added camelToSnakeCase filter.  
+  [Gyuri Grell](https://github.com/ggrell)
+  [#24](https://github.com/SwiftGen/StencilSwiftKit/pull/24)
 
 ### Internal Changes
 

Documentation/filters-strings.md

@@ -50,6 +50,29 @@ This filter accepts a parameter (boolean, default `false`) that controls the pre
 | SNAKE_CASE   | SnakeCase                |
 | __snake_case | SnakeCase                |
 
+## Filter: `camelToSnakeCase`
+
+Transforms text from camelCase to snake_case.
+
+| Input                 | Output                |
+|-----------------------|-----------------------|
+| SomeCapString         | some_cap_string       |
+| string_with_words     | string_with_words     |
+| STRing_with_words     | st_ring_with_words    |
+| URLChooser            | url_chooser           |
+| PLEASE_STOP_SCREAMING | please_stop_screaming |
+
+By default it converts to lower case, unless a single optional argument is set to "false", "no" or "0":
+
+| Input                  | Output                   |
+|------------------------|--------------------------|
+| SomeCapString          | Some_Cap_String          |
+| someCapString          | some_Cap_String          |
+| String_With_WoRds      | String_With_Wo_Rds       |
+| string_wiTH_WOrds      | string_wi_TH_W_Ords      |
+| URLChooser             | URL_Chooser              |
+| PLEASE_STOP_SCREAMING! | PLEASE_STOP_SCREAMING!   |
+
 ## Filter: `swiftIdentifier`
 
 Transforms an arbitrary string into a valid Swift identifier (using only valid characters for a Swift identifier as defined in the Swift language reference). It will apply the following rules:

README.md

@@ -16,7 +16,7 @@
   * Calls a previously defined macro, passing it some arguments
 * [Set](Documentation/tag-set.md)
   * `{% set <Name> %}…{% endset %}`
-  * Renders the nodes inside this block immediately, and stores the result in the `<Name`>  variable of the current context.
+  * Renders the nodes inside this block immediately, and stores the result in the `<Name>`  variable of the current context.
 * [Map](Documentation/tag-map.md)
   * `{% map <Variable> into <Name> using <ItemName> %}…{% endmap %}`
   * Apply a `map` operator to an array, and store the result into a new array variable `<Name>` in the current context.
@@ -29,6 +29,7 @@
   * `escapeReservedKeywords`: Escape keywods reserved in the Swift language, by wrapping them inside backticks so that the can be used as regular escape keywords in Swift code.
   * `lowerFirstWord`
   * `snakeToCamelCase` / `snakeToCamelCaseNoPrefix`
+  * `camelToSnakeCase`: Transforms text from camelCase to snake_case. By default it converts to lower case, unless a single optional argument is set to "false", "no" or "0".
   * `swiftIdentifier`: Transforms an arbitrary string into a valid Swift identifier (using only valid characters for a Swift identifier as defined in the Swift language reference)
   * `titlecase`
 * [Number filters](Documentation/filters-numbers.md):

Sources/Environment.swift

@@ -17,6 +17,7 @@ public extension Extension {
     registerFilter("lowerFirstWord", filter: StringFilters.lowerFirstWord)
     registerFilter("snakeToCamelCase", filter: StringFilters.snakeToCamelCase)
     registerFilter("snakeToCamelCaseNoPrefix", filter: StringFilters.snakeToCamelCaseNoPrefix)
+    registerFilter("camelToSnakeCase", filter: StringFilters.camelToSnakeCase)
     registerFilter("titlecase", filter: StringFilters.titlecase)
     registerFilter("hexToInt", filter: NumFilters.hexToInt)
     registerFilter("int255toFloat", filter: NumFilters.int255toFloat)

Sources/Filters.swift

@@ -11,6 +11,35 @@ enum FilterError: Error {
   case invalidInputType
 }
 
+enum Filters {
+  /// Parses filter arguments for a boolean value, where true can by any one of: "true", "yes", "1", and
+  /// false can be any one of: "false", "no", "0". If optional is true it means that the argument on the filter is
+  /// optional and it's not an error condition if the argument is missing or not the right type
+  /// - parameter arguments: an array of argument values, may be empty
+  /// - parameter index: the index in the arguments array
+  /// - parameter required: If true, the argument is required and function throws if missing.
+  ///                       If false, returns nil on missing args.
+  /// - returns: true or false if a value was parsed, or nil if it wasn't able to
+  static func parseBool(from arguments: [Any?], index: Int, required: Bool = true) throws -> Bool? {
+    guard index < arguments.count, let boolArg = arguments[index] as? String else {
+      if required {
+        throw FilterError.invalidInputType
+      } else {
+        return nil
+      }
+    }
+
+    switch boolArg.lowercased() {
+    case "false", "no", "0":
+      return false
+    case "true", "yes", "1":
+      return true
+    default:
+      throw FilterError.invalidInputType
+    }
+  }
+}
+
 struct StringFilters {
   fileprivate static let reservedKeywords = ["associatedtype", "class", "deinit", "enum", "extension",
                                          "fileprivate", "func", "import", "init", "inout", "internal",
@@ -89,6 +118,23 @@ struct StringFilters {
     }
   }
 
+  /// Converts camelCase to snake_case. Takes an optional Bool argument for making the string lower case,
+  /// which defaults to true
+  /// - parameter value: the value to be processed
+  /// - parameter arguments: the arguments to the function, expecting zero or one argument
+  /// - returns: the snake case string
+  /// - throws: FilterError.invalidInputType if the value parameter isn't a string
+  static func camelToSnakeCase(_ value: Any?, arguments: [Any?]) throws -> Any? {
+    let toLower = try Filters.parseBool(from: arguments, index: 0, required: false) ?? true
+    guard let string = value as? String else { throw FilterError.invalidInputType }
+
+    let snakeCase = try snakecase(string)
+    if toLower {
+      return snakeCase.lowercased()
+    }
+    return snakeCase
+  }
+
   /**
   This returns the string with its first parameter uppercased.
   - note: This is quite similar to `capitalise` except that this filter doesn't lowercase

StencilSwiftKit.xcodeproj/project.pbxproj

@@ -8,6 +8,7 @@
 
 /* Begin PBXBuildFile section */
 		82EF0CC0752D216C67279A16 /* Pods_Tests.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 8BF798509C76E5A9ACE03491 /* Pods_Tests.framework */; };
+		B5A3F2ED5DA57C06EF62BB82 /* ParseBoolTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = B5A3FFC01B2145C4BFD8316A /* ParseBoolTests.swift */; };
 		DD4393FF1E2D3EEB0047A332 /* MapNodeTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = DD4393FE1E2D3EEB0047A332 /* MapNodeTests.swift */; };
 		DD5F341B1E21993A00AEB5DA /* TestsHelper.swift in Sources */ = {isa = PBXBuildFile; fileRef = DD5F341A1E21993A00AEB5DA /* TestsHelper.swift */; };
 		DD5F342E1E21A3A200AEB5DA /* CallNodeTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = DD5F342A1E21A3A200AEB5DA /* CallNodeTests.swift */; };
@@ -57,6 +58,7 @@
 		47888DD528DEC4C84FD8F15B /* Pods-Tests.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Tests.debug.xcconfig"; path = "Pods/Target Support Files/Pods-Tests/Pods-Tests.debug.xcconfig"; sourceTree = "<group>"; };
 		4B3D39DBCD15D8F6BB891D92 /* Pods-Tests.release.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Tests.release.xcconfig"; path = "Pods/Target Support Files/Pods-Tests/Pods-Tests.release.xcconfig"; sourceTree = "<group>"; };
 		8BF798509C76E5A9ACE03491 /* Pods_Tests.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Pods_Tests.framework; sourceTree = BUILT_PRODUCTS_DIR; };
+		B5A3FFC01B2145C4BFD8316A /* ParseBoolTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ParseBoolTests.swift; sourceTree = "<group>"; };
 		DD4393FE1E2D3EEB0047A332 /* MapNodeTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MapNodeTests.swift; sourceTree = "<group>"; };
 		DD5F341A1E21993A00AEB5DA /* TestsHelper.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = TestsHelper.swift; sourceTree = "<group>"; };
 		DD5F34201E2199ED00AEB5DA /* Info.plist */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
@@ -148,6 +150,7 @@
 				DD5F342D1E21A3A200AEB5DA /* SwiftIdentifierTests.swift */,
 				DD5F341A1E21993A00AEB5DA /* TestsHelper.swift */,
 				DD5F341C1E2199ED00AEB5DA /* Resources */,
+				B5A3FFC01B2145C4BFD8316A /* ParseBoolTests.swift */,
 			);
 			path = StencilSwiftKitTests;
 			sourceTree = "<group>";
@@ -299,6 +302,7 @@
 				DDFD1F691E5358C70023AE2B /* ContextTests.swift in Sources */,
 				DD5F342E1E21A3A200AEB5DA /* CallNodeTests.swift in Sources */,
 				DDE1E2F91E3FABE70043367C /* ParametersTests.swift in Sources */,
+				B5A3F2ED5DA57C06EF62BB82 /* ParseBoolTests.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

Tests/StencilSwiftKitTests/ParseBoolTests.swift

@@ -0,0 +1,76 @@
+//
+// StencilSwiftKit
+// Copyright (c) 2017 SwiftGen
+// MIT Licence
+//
+
+import XCTest
+@testable import StencilSwiftKit
+
+class ParseBoolTests: XCTestCase {
+
+  func testParseBool_WithTrueString() throws {
+    let value = try Filters.parseBool(from: ["true"], index: 0)
+    XCTAssertTrue(value!)
+  }
+
+  func testParseBool_WithFalseString() throws {
+    let value = try Filters.parseBool(from: ["false"], index: 0)
+    XCTAssertFalse(value!)
+  }
+
+  func testParseBool_WithYesString() throws {
+    let value = try Filters.parseBool(from: ["yes"], index: 0)
+    XCTAssertTrue(value!)
+  }
+
+  func testParseBool_WithNoString() throws {
+    let value = try Filters.parseBool(from: ["no"], index: 0)
+    XCTAssertFalse(value!)
+  }
+
+  func testParseBool_WithOneString() throws {
+    let value = try Filters.parseBool(from: ["1"], index: 0)
+    XCTAssertTrue(value!)
+  }
+
+  func testParseBool_WithZeroString() throws {
+    let value = try Filters.parseBool(from: ["0"], index: 0)
+    XCTAssertFalse(value!)
+  }
+
+  func testParseBool_WithOptionalInt() throws {
+    let value = try Filters.parseBool(from: [1], index: 0, required: false)
+    XCTAssertNil(value)
+  }
+
+  func testParseBool_WithRequiredInt() throws {
+    XCTAssertThrowsError(try Filters.parseBool(from: [1], index: 0, required: true))
+  }
+
+  func testParseBool_WithOptionalDouble() throws {
+    let value = try Filters.parseBool(from: [1.0], index: 0, required: false)
+    XCTAssertNil(value)
+  }
+
+  func testParseBool_WithRequiredDouble() throws {
+    XCTAssertThrowsError(try Filters.parseBool(from: [1.0], index: 0, required: true))
+  }
+
+  func testParseBool_WithEmptyString() throws {
+    XCTAssertThrowsError(try Filters.parseBool(from: [""], index: 0, required: false))
+  }
+
+  func testParseBool_WithEmptyStringAndRequiredArg() throws {
+    XCTAssertThrowsError(try Filters.parseBool(from: [""], index: 0, required: true))
+  }
+
+  func testParseBool_WithEmptyArray() throws {
+    let value = try Filters.parseBool(from: [], index: 0, required: false)
+    XCTAssertNil(value)
+  }
+
+  func testParseBool_WithEmptyArrayAndRequiredArg() throws {
+    XCTAssertThrowsError(try Filters.parseBool(from: [], index: 0, required: true))
+  }
+}

Tests/StencilSwiftKitTests/StringFiltersTests.swift

@@ -133,6 +133,77 @@ class StringFiltersTests: XCTestCase {
     }
   }
 
+  func testCamelToSnakeCase_WithNoArgsDefaultsToTrue() throws {
+    let result = try StringFilters.camelToSnakeCase("StringWithWords", arguments: []) as? String
+    XCTAssertEqual(result, "string_with_words")
+  }
+
+  func testCamelToSnakeCase_WithTrue() throws {
+    let expectations = [
+      "string": "string",
+      "String": "string",
+      "strIng": "str_ing",
+      "strING": "str_ing",
+      "X": "x",
+      "x": "x",
+      "SomeCapString": "some_cap_string",
+      "someCapString": "some_cap_string",
+      "string_with_words": "string_with_words",
+      "String_with_words": "string_with_words",
+      "String_With_Words": "string_with_words",
+      "String_With_WoRds": "string_with_wo_rds",
+      "STRing_with_words": "st_ring_with_words",
+      "string_wiTH_WOrds": "string_wi_th_w_ords",
+      "": "",
+      "URLChooser": "url_chooser",
+      "UrlChooser": "url_chooser",
+      "a__b__c": "a__b__c",
+      "__y_z!": "__y_z!",
+      "PLEASESTOPSCREAMING": "pleasestopscreaming",
+      "PLEASESTOPSCREAMING!": "pleasestopscreaming!",
+      "PLEASE_STOP_SCREAMING": "please_stop_screaming",
+      "PLEASE_STOP_SCREAMING!": "please_stop_screaming!"
+    ]
+
+    for (input, expected) in expectations {
+      let trueArgResult = try StringFilters.camelToSnakeCase(input, arguments: ["true"]) as? String
+      XCTAssertEqual(trueArgResult, expected)
+    }
+  }
+
+  func testCamelToSnakeCase_WithFalse() throws {
+    let expectations = [
+      "string": "string",
+      "String": "String",
+      "strIng": "str_Ing",
+      "strING": "str_ING",
+      "X": "X",
+      "x": "x",
+      "SomeCapString": "Some_Cap_String",
+      "someCapString": "some_Cap_String",
+      "string_with_words": "string_with_words",
+      "String_with_words": "String_with_words",
+      "String_With_Words": "String_With_Words",
+      "String_With_WoRds": "String_With_Wo_Rds",
+      "STRing_with_words": "ST_Ring_with_words",
+      "string_wiTH_WOrds": "string_wi_TH_W_Ords",
+      "": "",
+      "URLChooser": "URL_Chooser",
+      "UrlChooser": "Url_Chooser",
+      "a__b__c": "a__b__c",
+      "__y_z!": "__y_z!",
+      "PLEASESTOPSCREAMING": "PLEASESTOPSCREAMING",
+      "PLEASESTOPSCREAMING!": "PLEASESTOPSCREAMING!",
+      "PLEASE_STOP_SCREAMING": "PLEASE_STOP_SCREAMING",
+      "PLEASE_STOP_SCREAMING!": "PLEASE_STOP_SCREAMING!"
+    ]
+
+    for (input, expected) in expectations {
+      let falseArgResult = try StringFilters.camelToSnakeCase(input, arguments: ["false"]) as? String
+      XCTAssertEqual(falseArgResult, expected)
+    }
+  }
+
   func testEscapeReservedKeywords() throws {
     let expectations = [
       "self": "`self`",