Add article and tutorial about Spell Checking to the Custom Language Support topic (#856)

- Add two articles about spell checking for the Custom Language Support topic
- Reference part describing general information about spell checking
- Implementation part with spell checking strategy for the Simple language
- Add info about EP for `BundledDictionaryProvider`
- Add `SuppressibleSpellcheckingStrategy` section

simple_language_plugin/src/main/java/org/intellij/sdk/language/SimpleSpellcheckingStrategy.java

@@ -0,0 +1,80 @@
+// Copyright 2000-2022 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license.
+
+package org.intellij.sdk.language;
+
+import com.intellij.lang.ASTNode;
+import com.intellij.openapi.util.TextRange;
+import com.intellij.psi.PsiComment;
+import com.intellij.psi.PsiElement;
+import com.intellij.spellchecker.inspections.CommentSplitter;
+import com.intellij.spellchecker.inspections.IdentifierSplitter;
+import com.intellij.spellchecker.inspections.PlainTextSplitter;
+import com.intellij.spellchecker.tokenizer.SpellcheckingStrategy;
+import com.intellij.spellchecker.tokenizer.TokenConsumer;
+import com.intellij.spellchecker.tokenizer.Tokenizer;
+import org.intellij.sdk.language.psi.SimpleProperty;
+import org.intellij.sdk.language.psi.SimpleTypes;
+import org.jetbrains.annotations.NotNull;
+
+public class SimpleSpellcheckingStrategy extends SpellcheckingStrategy {
+
+    @Override
+    public @NotNull Tokenizer<?> getTokenizer(PsiElement element) {
+        if (element instanceof PsiComment) {
+            return new SimpleCommentTokenizer();
+        }
+
+        if (element instanceof SimpleProperty) {
+            return new SimplePropertyTokenizer();
+        }
+
+        return EMPTY_TOKENIZER;
+    }
+
+    private static class SimpleCommentTokenizer extends Tokenizer<PsiComment> {
+
+        @Override
+        public void tokenize(@NotNull PsiComment element, TokenConsumer consumer) {
+            // Exclude the start of the comment with its # characters from spell checking
+            int startIndex = 0;
+            for (char c : element.textToCharArray()) {
+                if (c == '#' || Character.isWhitespace(c)) {
+                    startIndex++;
+                } else {
+                    break;
+                }
+            }
+            consumer.consumeToken(element, element.getText(), false, 0,
+                    TextRange.create(startIndex, element.getTextLength()),
+                    CommentSplitter.getInstance());
+        }
+
+    }
+
+    private static class SimplePropertyTokenizer extends Tokenizer<SimpleProperty> {
+
+        public void tokenize(@NotNull SimpleProperty element, TokenConsumer consumer) {
+            //Spell check the keys and values of properties with different splitters
+            final ASTNode key = element.getNode().findChildByType(SimpleTypes.KEY);
+            if (key != null && key.getTextLength() > 0) {
+                final PsiElement keyPsi = key.getPsi();
+                final String text = key.getText();
+                //For keys, use a splitter for identifiers
+                //Note we set "useRename" to true so that keys will be properly refactored (renamed)
+                consumer.consumeToken(keyPsi, text, true, 0,
+                        TextRange.allOf(text), IdentifierSplitter.getInstance());
+            }
+
+            final ASTNode value = element.getNode().findChildByType(SimpleTypes.VALUE);
+            if (value != null && value.getTextLength() > 0) {
+                final PsiElement valuePsi = value.getPsi();
+                final String text = valuePsi.getText();
+                //For values, use a splitter for plain text
+                consumer.consumeToken(valuePsi, text, false, 0,
+                        TextRange.allOf(text), PlainTextSplitter.getInstance());
+            }
+        }
+
+    }
+
+}

simple_language_plugin/src/main/resources/META-INF/plugin.xml

@@ -71,6 +71,7 @@
     <langCodeStyleSettingsProvider implementation="org.intellij.sdk.language.SimpleLanguageCodeStyleSettingsProvider"/>
     <lang.commenter language="Simple" implementationClass="org.intellij.sdk.language.SimpleCommenter"/>
     <lang.documentationProvider language="Simple" implementationClass="org.intellij.sdk.language.SimpleDocumentationProvider"/>
+    <spellchecker.support language="Simple" implementationClass="org.intellij.sdk.language.SimpleSpellcheckingStrategy"/>
   </extensions>
 
 </idea-plugin>