Auto-closing braces in a custom language, BraceMatcher not working

Try to debug com.intellij.codeInsight.editorActions.TypedHandler#handleAfterLParen method.

I had this same problem because I was trying to match angle brackets ("<>"), and after doing some I discovered that in com.intellij.codeInsight.editorActions.TypedHandler#handleAfterLParen(), it checks to see if an angle bracket was inputted:

if (!matched) {
  String text;
  if (lparenChar == '(') {
    text = ")";
  }
  else if (lparenChar == '[') {
    text = "]";
  }
  else if (lparenChar == '<') {
    text = ">";
  }
  else if (lparenChar == '{') {
    text = "}";
  }
  else {
    throw new AssertionError("Unknown char "+lparenChar);
  }
  editor.getDocument().insertString(offset, text);
  TabOutScopesTracker.getInstance().registerEmptyScope(editor, offset);
}

BUT! It only ever gets called in com.intellij.codeInsight.editorActions.TypedHandler#execute() like this:

if (('(' == charTyped || '[' == charTyped || '{' == charTyped) &&
  CodeInsightSettings.getInstance().AUTOINSERT_PAIR_BRACKET &&
  fileType != FileTypes.PLAIN_TEXT) {
  handleAfterLParen(editor, fileType, charTyped);
}

Notice that lparenChar can never be "<" because handleAfterParen() only gets called if the character typed is "(", "[", or "{". So this seems to me to be a bug, because "<" can be matched pretty often. Although, it would make sense to me to allow ANY brace pairs specified in the PairedBraceMatcher to be auto-paired instead of just the 3 or 4 specified here. For example, if you a brace pair for ("BEGIN", "END") and you wrote "Here's my story BEGIN", intellij would automatically add "END" after your caret.

But if they never fix this, the way I solved it was by implementing a TypedHandlerDelegate (which can be added the plugin with the com.intellij.lang.typedHandler extension) then basically copied the code from handleAfterLParen and adjusted it to my needs into the charTyped() method.

I'm facing the same issue, basically the same code as yours but none of the braces (i.e {, (, [) get completion and isPairedBracesAllowedBeforeType doesn't get invoked at all. Does it have any prerequisites? Do I have to add anything other than braceMatcher in plugin.xml or anywhere else in the codebase?

Have you found a solution to this problem?

I faced the same issue and looked at the java plugin for reference. They add a custom TypedHandlerDelegate to handle this case. An implementation might look like this

// Extension point name: typedHandler
class MyLanguageBraceMatchingTypedHandler : TypedHandlerDelegate() {

    private var ltTyped = false

    override fun beforeCharTyped(c: Char, project: Project, editor: Editor, file: PsiFile, fileType: FileType): Result {
        if (file !is MyLanguagePsiFile) return Result.CONTINUE

        ltTyped = c == '<' && TypedHandlerUtil.isAfterClassLikeIdentifierOrDot(
            editor.caretModel.offset,
            editor,
            MyLanguageTokenTypes.IDENTIFIER,
            MyLanguageTokenTypes.IDENTIFIER,
            true
        ) && CodeInsightSettings.getInstance().AUTOINSERT_PAIR_BRACKET

        if (c == '>' && TypedHandlerUtil.handleGenericGT(
                editor,
                MyLanguageTokenTypes.LESS,
                MyLanguageTokenTypes.GREATER,
                INVALID_INSIDE_REFERENCE
            ) && CodeInsightSettings.getInstance().AUTOINSERT_PAIR_BRACKET
        ) return Result.STOP

        return Result.CONTINUE
    }

    override fun charTyped(c: Char, project: Project, editor: Editor, file: PsiFile): Result {
        if (file !is MyLanguagePsiFile || !ltTyped) return Result.CONTINUE

        ltTyped = false
        TypedHandlerUtil.handleAfterGenericLT(
            editor,
            MyLanguageTokenTypes.LESS,
            MyLanguageTokenTypes.GREATER,
            INVALID_INSIDE_REFERENCE
        )

        return Result.STOP
    }

    companion object {
        val INVALID_INSIDE_REFERENCE = TokenSet.create(
            MyLanguageTokenTypes.L_PAREN,
            MyLanguageTokenTypes.R_PAREN,
            MyLanguageTokenTypes.L_CURLY_PAREN,
            MyLanguageTokenTypes.R_CURLY_PAREN
        )
    }
}

I recommend looking at the docs and implementation of TypedHandlerUtil to get a better understanding of this code snippet.

References:

https://github.com/JetBrains/intellij-community/blob/master/java/java-impl/src/com/intellij/codeInsight/editorActions/JavaTypedHandler.java#L109-L119 

https://github.com/JetBrains/intellij-community/blob/3a9d9eccaf61e4583d46d889698a09f681647208/java/java-impl/src/com/intellij/codeInsight/editorActions/JavaTypedHandler.java#L327

Additionally, I can recommend adapting their brace matcher as well if you don't want highlighted braces for </> in normal expressions. You might only want this for generic parameter as an example. This can be achieved with a custom brace matcher like this (requires dependency on "com.intellij.java")

// Extension point name: lang.braceMatcher
class MyLanguagePairedBraceMatcher : PairedBraceAndAnglesMatcher(MyLanguageBraceMatcher(), MyLanguageLanguage.INSTANCE, MyLanguageLanguageFileType.INSTANCE, ALLOWED_INSIDE_ANGLES) {

    override fun lt(): IElementType = MyLanguageTokenTypes.LESS

    override fun gt(): IElementType = MyLanguageTokenTypes.GREATER

    companion object {
        val ALLOWED_INSIDE_ANGLES = TokenSet.create(MyLanguageTokenTypes.IDENTIFIER, MyLanguageTokenTypes.COMMA, TokenType.WHITE_SPACE)
    }
}

Reference:

https://github.com/JetBrains/intellij-community/blob/6dec3dca0e3675e048dc3665a99f65721c584e42/java/java-impl/src/com/intellij/codeInsight/highlighting/JavaPairedBraceMatcher.java