Fix support for caching nspell suggestions

Closes GH-21.
Closes GH-22.

Reviewed-by: Titus Wormer <tituswormer@gmail.com>

index.js

@@ -148,13 +148,14 @@ function all(tree, file, config) {
     }
 
     if (!correct) {
+      reason = quote(word, '`') + ' is misspelt'
+
       // Suggestions are very slow, so cache them (spelling mistakes other than
       // typos often occur multiple times).
       if (own.call(cache, word)) {
-        reason = cache[word]
+        suggestions = cache[word]
+        reason = concatPrefixToSuggestions(reason, suggestions)
       } else {
-        reason = quote(word, '`') + ' is misspelt'
-
         if (config.count === config.max) {
           file.message(
             'Too many misspellings; no further spell suggestions are given',
@@ -169,13 +170,11 @@ function all(tree, file, config) {
           suggestions = checker.suggest(word)
 
           if (suggestions.length !== 0) {
-            reason +=
-              '; did you mean ' + quote(suggestions, '`').join(', ') + '?'
-            cache[word] = reason
+            reason = concatPrefixToSuggestions(reason, suggestions)
           }
         }
 
-        cache[word] = reason
+        cache[word] = suggestions || []
       }
 
       message = file.message(
@@ -188,6 +187,11 @@ function all(tree, file, config) {
     }
   }
 
+  // Concatenate the formatted suggestions to a given prefix
+  function concatPrefixToSuggestions(prefix, suggestions) {
+    return prefix + '; did you mean ' + quote(suggestions, '`').join(', ') + '?'
+  }
+
   // Check if a word is irrelevant.
   function irrelevant(word) {
     return (

test.js

@@ -120,6 +120,43 @@ test('should warn for invalid words (coverage)', function (t) {
   })
 })
 
+test('should cache suggestions', function (t) {
+  t.plan(2)
+
+  const retextSpell = retext().use(spell, enGb)
+
+  const numberOfChecks = 2
+
+  for (let i = 0; i < numberOfChecks; i += 1) {
+    retextSpell.process('color', function (_, file) {
+      t.deepEqual(
+        JSON.parse(JSON.stringify(file.messages)),
+        [
+          {
+            message:
+              '`color` is misspelt; did you mean `colon`, `colour`, `Colo`?',
+            name: '1:1-1:6',
+            reason:
+              '`color` is misspelt; did you mean `colon`, `colour`, `Colo`?',
+            line: 1,
+            column: 1,
+            location: {
+              start: {line: 1, column: 1, offset: 0},
+              end: {line: 1, column: 6, offset: 5}
+            },
+            source: 'retext-spell',
+            ruleId: 'color',
+            fatal: false,
+            actual: 'color',
+            expected: ['colon', 'colour', 'Colo']
+          }
+        ],
+        'should emit messages'
+      )
+    })
+  }
+})
+
 test('should support `max`, for maximum suggestions', function (t) {
   t.plan(1)