Support for lexer grammar

[moy]

I'm currently using org.antlr.v4.gui.TestRig for ANTLR teaching to help students debug simple grammars. Since my course uses Python, I'd rather avoid exposing students to Java stuff.

antlr4-parse looks very much like what I'm looking for, but doesn't seem to work for lexer grammars:

With TestRig, I can do:

$ cat Tokens.g4
lexer grammar Tokens;

HELLO : 'hello' ;         // beware the single quotes
ID : [a-z]+ ;             // match lower-case identifiers
INT : [0-9]+ ;
KEYWORD : 'begin' | 'end' | 'for' ; // perhaps this should be elsewhere
WS : [ \t\r\n]+ -> skip ; // skip spaces, tabs, newlines
$ antlr4 Tokens.g4 && javac *.java
$ echo hello | java org.antlr.v4.gui.TestRig Tokens tokens -tokens
[@0,0:4='hello',<'hello'>,1:0]
[@1,6:5='<EOF>',<EOF>,2:0]

However, it crashes when I try antlr4-parse:

$ antlr4-parse Tokens.g4 tokens -tokens 
Exception in thread "main" java.lang.ClassCastException: class org.antlr.v4.gui.Interpreter$IgnoreTokenVocabGrammar cannot be cast to class org.antlr.v4.tool.LexerGrammar (org.antlr.v4.gui.Interpreter$IgnoreTokenVocabGrammar and org.antlr.v4.tool.LexerGrammar are in unnamed module of loader 'app')
        at org.antlr.v4.semantics.SymbolChecks.checkForModeConflicts(SymbolChecks.java:313)
        at org.antlr.v4.semantics.SemanticPipeline.process(SemanticPipeline.java:110)
        at org.antlr.v4.Tool.processNonCombinedGrammar(Tool.java:371)
        at org.antlr.v4.Tool.process(Tool.java:359)
        at org.antlr.v4.tool.Grammar.<init>(Grammar.java:364)
        at org.antlr.v4.gui.Interpreter$IgnoreTokenVocabGrammar.<init>(Interpreter.java:42)
        at org.antlr.v4.gui.Interpreter.interp(Interpreter.java:141)
        at org.antlr.v4.gui.Interpreter.main(Interpreter.java:277)