Change CustomMarkers 'null' value

Goal: The JS code currently needs to import the CustomMarkers
type/constructor from Types.js. Remove this need so that Main.js can be
the single point of entry, which will make it easier when bundling up
the core with Parcel etc.

Removing the AllowNullLiteral attribute from the CustomMarkers type and
making it a plain record, as well as removing the Option types from that
record, means it can be more easily created in C# code, and created as a
POJO in JS code.

The Option types on the line & block members were also redundant, since
an empty string is also an empty (invalid) value. Empty strings were not
checked-for in addCustomLanguage, leading to a runtime error if they
were supplied.

Now addCustomLanguage is changed to maybeAddCustomLanguage, and it only
adds the language if it has a valid line or block member.

core.test/Tests.fs

@@ -243,7 +243,7 @@ let printFailure (test: Test) (actual: Lines) =
 /// Runs a test
 let runTest (test: Test) =
   let getLine = Func<int,string>(fun i -> if i < test.input.Length then test.input.[i] else null)
-  let file = { language = test.language; path = ""; getMarkers = Func<CustomMarkers>(fun () -> null) }
+  let file = {language = test.language; path = ""; getMarkers = Func<CustomMarkers>(fun () -> {line = ""; block = ("","")})}
   let edit = Core.rewrap file test.settings test.selections getLine
   let actual = applyEdit edit test.input
   let arrayEqual (a: 'a[]) (b: 'a[]) = (a.Length = b.Length && not (Seq.exists2 (fun x y -> x <> y) a b))

core/Parsing.Documents.fs

@@ -277,15 +277,20 @@ let mutable languages = [
         )
     ]
 
-/// Creates a custom language parser. Also adds it to the list of languages
-let private addCustomLanguage name (markers: CustomMarkers) =
+/// Creates a custom language parser, if the given CustomMarkers are valid. Also
+/// adds it to the list of languages
+let private maybeAddCustomLanguage name (markers: CustomMarkers) : Option<Language> =
     let escape = System.Text.RegularExpressions.Regex.Escape
-    let maybeLine = map (line << escape) markers.line
-    let maybeBlock = map (block << map escape) markers.block
-    let list = maybe [] List.singleton maybeBlock @ maybe [] List.singleton maybeLine
+    let isInvalid = String.IsNullOrEmpty
+    let maybeLine = if isInvalid markers.line then None else Some (line (escape markers.line))
+    let maybeBlock =
+      if isInvalid (fst markers.block) || isInvalid (snd markers.block) then None
+      else Some (block (map escape markers.block))
+    let list = [maybeBlock; maybeLine] |> List.choose id
+    if List.isEmpty list then None else
     let cl = lang name "" "" (sourceCode list)
     languages <- cl :: languages
-    cl
+    Some cl
 
 /// Tries to find a known Language for the given File, using its language ID. If
 /// that is empty or the default ('plaintext'), it tries using the file's
@@ -310,9 +315,5 @@ let languageForFile (file: File) : Option<Language> =
 let rec select (file: File) : Settings -> TotalParser<string> =
     languageForFile file
         |> Option.orElseWith
-            (fun () ->
-                match file.getMarkers.Invoke() with
-                | null -> None
-                | x -> Some (addCustomLanguage file.language x)
-            )
+            (fun () -> maybeAddCustomLanguage file.language (file.getMarkers.Invoke()))
         |> maybe plainText Language.parser

core/Types.fs

@@ -2,10 +2,11 @@ namespace Rewrap
 
 open System
 
-[<AllowNullLiteral>]
-type CustomMarkers(line: Option<string>, block: Option<string * string>) =
-    member this.line = line
-    member this.block = block
+// Set of comment markers provided by the editor to create a custom language. To
+// be valid, either `line` must be a nonempty string or `block` two nonempty
+// strings.
+type CustomMarkers = { line: string; block : string * string }
+
 
 /// File language and path. Used to select a parser.
 type File = { language: string; path: string; getMarkers: Func<CustomMarkers> }

tests.js

@@ -344,9 +344,10 @@ function runTests(tests)
 
         try {
             const getLine = i => i < input.length ? input[i] : null
+            const getMarkers = () => ({line: "", block: ["",""]})
             const edit =
                 Core.rewrap
-                    ( { language: settings.language, path: '', getMarkers: () => { } }
+                    ( { language: settings.language, path: '', getMarkers }
                     , Object.assign(settings, { column: wrappingColumn })
                     , selections
                     , getLine

vs/Editor.cs

@@ -24,7 +24,8 @@ public static void StandardWrap(IWpfTextView textView)
         {
             var textBuffer = textView.TextBuffer;
             var snapshot = textBuffer.CurrentSnapshot;
-            var file = new File(GetLanguage(textBuffer), GetFilePath(textBuffer), () => null);
+            var noCustomMarkers = new CustomMarkers("", Tuple.Create("", ""));
+            var file = new File(GetLanguage(textBuffer), GetFilePath(textBuffer), () => noCustomMarkers);
             DocState getDocState(ITextSnapshot ss) =>
                 new DocState(file.path, ss.Version.VersionNumber, GetSelections(textView, ss));
 

vscode/Core.ts

@@ -1,11 +1,7 @@
-const Types = require('./core/Types')
 const Main = require('./core/Main')
 
 
 export interface CustomMarkers { line: string, block: [string, string] }
-export interface CustomMarkersStatic {
-  new(line: string, block: string[]): CustomMarkers
-}
 
 export interface DocState { filePath: string, version: number, selections: Selection[] }
 
@@ -34,8 +30,6 @@ export interface Settings {
   wholeComment: boolean
 }
 
-export const CustomMarkers: CustomMarkersStatic = Types.CustomMarkers
-
 /** Gets the current wrapping column used for the given document */
 export const getWrappingColumn: (path: string, columns: number[]) => number =
   Main.getWrappingColumn

vscode/CustomLanguage.ts

@@ -1,7 +1,6 @@
 const Path = require('path')
 const FS = require('fs')
 const JSON = require('json5')
-const {CustomMarkers} = require('./core/Types')
 
 const getConfig = (getText, path) => {
     let config = {line: null, block: null}
@@ -61,14 +60,16 @@ export default function(exts?, getFileText?) {
 
     getFileText = getFileText || (p => FS.readFileSync(p))
     let cache = null
+    const noMarkers = {line: "", block: ["", ""]}
     return lang => {
         cache = cache || createCache(exts)
 
         if (typeof cache[lang] === 'string') {
             const config = getConfig(getFileText, cache[lang])
             cache[lang] = (config.line || config.block) ?
-                new CustomMarkers(config.line, config.block) : null
+                {line: config.line, block: config.block} : noMarkers
         }
+        else if (!cache[lang]) cache[lang] = noMarkers
         return cache[lang]
     }
 }