Source code for scenic.simulators.webots.world_parser

"""Parser for WBT files using ANTLR.

The ANTLR parser itself, consisting of the **, **, and ** files, is autogenerated from *WBT.g4*.

import sys
import io
import time

import numpy as np

import antlr4
from antlr4.error.ErrorListener import ErrorListener
from scenic.simulators.webots.WBTLexer import WBTLexer
from scenic.simulators.webots.WBTParser import WBTParser
from scenic.simulators.webots.WBTVisitor import WBTVisitor

### Setup

## Classes representing various types of VRML nodes 

[docs]class Node: """A generic VRML node""" def __init__(self, nodeType, attrs): self.nodeType = nodeType self.attrs = attrs
## Classes for parsing with ANTLR # Error handling
[docs]class ErrorReporter(ErrorListener): """ANTLR listener for reporting parse errors""" def syntaxError(self, recognizer, offendingSymbol, line, column, msg, e): raise Exception(f'Parse error at {line}:{column}: {msg}')
# Walking the parse tree and extracting values
[docs]class Evaluator(WBTVisitor): """Constructs an object representing the given value from the parse tree""" def __init__(self, nodeClasses): super().__init__() # Dictionary indicating which types of nodes have specialized classes self.nodeClasses = nodeClasses def visitNode(self, node): nodeType = node.Identifier().getText() attrs = self.visitNodeBody(node.nodeBody()) if nodeType in self.nodeClasses: nodeClass = self.nodeClasses[nodeType] nodeObj = nodeClass(attrs) else: nodeObj = Node(nodeType, attrs) return nodeObj def visitNodeBody(self, body): return {attr.Identifier().getText(): self.visitValue(attr.value()) for attr in body.attribute()} def visitValue(self, val): return self.visit(val.getChild(0)) def visitVector(self, vec): return np.array([float(n.getText()) for n in vec.Number()]) def visitVectorWithNewlines(self, vec): return self.visitVector(vec) def visitString(self, string): return string.getText()[1:-1] # strip off quotes def visitArray(self, array): return [self.visit(val) for val in array.children if not isinstance(val, antlr4.tree.Tree.TerminalNode)] def visitBoolean(self, boolean): return boolean.getText() == 'TRUE'
[docs]def parse(path): """Parse a world from a WBT file""" # Open file charStream = antlr4.FileStream(path) # Set up lexer and parser errorListener = ErrorReporter() lexer = WBTLexer(charStream) lexer.addErrorListener(errorListener) tokenStream = antlr4.CommonTokenStream(lexer) parser = WBTParser(tokenStream) parser.addErrorListener(errorListener) # Parse file return
[docs]def findNodeTypesIn(types, world, nodeClasses={}): """Find all nodes of the given types in a world""" evaluator = Evaluator(nodeClasses) types = tuple(types) instances = {ty: [] for ty in types} for node in world.children: if isinstance(node, WBTParser.DefnContext): node = node.node() nodeType = node.Identifier().getText() if nodeType in instances: val = evaluator.visitNode(node) instances[nodeType].append(val) return tuple(instances[ty] for ty in types)