Examples of ParseTreePatternMatcher

org.antlr.v4.runtime.tree.pattern.ParseTreePatternMatcher
A tree pattern matching mechanism for ANTLR {@link ParseTree}s.
Patterns are strings of source input text with special tags representing token or rule references such as:

{@code = ;}

Given a pattern start rule such as {@code statement}, this object constructs a {@link ParseTree} with placeholders for the {@code ID} and {@code expr}subtree. Then the {@link #match} routines can compare an actual{@link ParseTree} from a parse with this pattern. Tag {@code } matchesany {@code ID} token and tag {@code } references the result of the{@code expr} rule (generally an instance of {@code ExprContext}.

Pattern {@code x = 0;} is a similar pattern that matches the same patternexcept that it requires the identifier to be {@code x} and the expression tobe {@code 0}.

The {@link #matches} routines return {@code true} or {@code false} basedupon a match for the tree rooted at the parameter sent in. The {@link #match} routines return a {@link ParseTreeMatch} object thatcontains the parse tree, the parse tree pattern, and a map from tag name to matched nodes (more below). A subtree that fails to match, returns with {@link ParseTreeMatch#mismatchedNode} set to the first tree node that did notmatch.

For efficiency, you can compile a tree pattern in string form to a {@link ParseTreePattern} object.
See {@code TestParseTreeMatcher} for lots of examples.{@link ParseTreePattern} has two static helper methods:{@link ParseTreePattern#findAll} and {@link ParseTreePattern#match} thatare easy to use but not super efficient because they create new {@link ParseTreePatternMatcher} objects each time and have to compile thepattern in string form before using it.

The lexer and parser that you pass into the {@link ParseTreePatternMatcher}constructor are used to parse the pattern in string form. The lexer converts the {@code = ;} into a sequence of four tokens (assuming lexerthrows out whitespace or puts it on a hidden channel). Be aware that the input stream is reset for the lexer (but not the parser; a {@link ParserInterpreter} is created to parse the input.). Any user-definedfields you have put into the lexer might get changed when this mechanism asks it to scan the pattern string.

Normally a parser does not accept token {@code } as a valid{@code expr} but, from the parser passed in, we create a special version ofthe underlying grammar representation (an {@link ATN}) that allows imaginary tokens representing rules ( {@code }) to match entire rules. We call these bypass alternatives.

Delimiters are {@code <} and {@code>}, with {@code \} as the escape stringby default, but you can set them to whatever you want using {@link #setDelimiters}. You must escape both start and stop strings {@code \<} and {@code \>}.

Examples of org.antlr.v4.runtime.tree.pattern.ParseTreePatternMatcher

      "WS : [ \\r\\n\\t]+ -> skip ;\n";
    boolean ok =
      rawGenerateAndBuildRecognizer("X2.g4", grammar, "X2Parser", "X2Lexer", false);
    assertTrue(ok);


    ParseTreePatternMatcher m = getPatternMatcher("X2");


    boolean failed = false;
    try {
      m.compile("<ID> <ID> ;", m.getParser().getRuleIndex("s"));
    }
    catch (NoViableAltException e) {
      failed = true;
    }
    assertTrue(failed);

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Examples of org.antlr.v4.runtime.tree.pattern.ParseTreePatternMatcher

      "WS : [ \\r\\n\\t]+ -> channel(HIDDEN) ;\n";
    boolean ok =
      rawGenerateAndBuildRecognizer("X2.g4", grammar, "X2Parser", "X2Lexer", false);
    assertTrue(ok);


    ParseTreePatternMatcher m = getPatternMatcher("X2");


    ParseTreePattern t = m.compile("<ID> = <expr> ;", m.getParser().getRuleIndex("s"));
    String results = t.getPatternTree().toStringTree(m.getParser());
    String expected = "(s <ID> = (expr <expr>) ;)";
    assertEquals(expected, results);
  }

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Examples of org.antlr.v4.runtime.tree.pattern.ParseTreePatternMatcher

      "WS : [ \\r\\n\\t]+ -> skip ;\n";
    boolean ok =
      rawGenerateAndBuildRecognizer("X2.g4", grammar, "X2Parser", "X2Lexer", false);
    assertTrue(ok);


    ParseTreePatternMatcher m =  getPatternMatcher("X2");


    ParseTreePattern t = m.compile("<ID> = <ID> ;", m.getParser().getRuleIndex("s"));
    String results = t.getPatternTree().toStringTree(m.getParser());
    String expected = "(s <ID> = <ID> ;)";
    assertEquals(expected, results);
  }

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Examples of org.antlr.v4.runtime.tree.pattern.ParseTreePatternMatcher


    Class<? extends Parser> parserClass = loadParserClassFromTempDir(grammarName + "Parser");
    Constructor<? extends Parser> pctor = parserClass.getConstructor(TokenStream.class);
    Parser parser = pctor.newInstance(new CommonTokenStream(lexer));


    return new ParseTreePatternMatcher(lexer, parser);
  }

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