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WebIDL Parser

Project description

widlparser

Stand-alone WebIDL Parser in Python. Requires Python 3.7+.

Parses WebIDL per: http://dev.w3.org/2006/webapi/WebIDL/ (plus a few legacy compatability items)

This parser was created to support a W3C specification parser and pre-processor, it's API is geared towards finding and identifying various WebIDL constructs by name. However, all of the WebIDL source is parsed and stored in the construct objects. The parser has error recovery and preserves the entire input for re-serialization and markup of the WebIDL constructs.

Installation

Standard python package installation:

pip install widlparser3

or

python setup.py install

Usage

Import the widlparser package and instantiate a Parser.

import widlparser

widl = widlparser.Parser()

Either pass the WebIDL text to be parsed in the constructor or call the Parser.parse(text) method.

Parser class

class Parser([text[, ui]])

The Parser's constructor takes two optional arguments, text and ui. If present, text is a string containing the WebIDL text to parse. ui.warn() will get called with any syntax errors encountered during parsing (if implemented). ui.note() will get called for any legacy WebIDL that was ignored during parsing (if implemented).

Parser.constructs

All top-level WebIDL constructs are stored in source order in the 'constructs' attribute.

Parser.complexity_factor

An index of the relative complexity of the Constructs defined in the parsed WebIDL. Useful as an index for specification test coverage

Parser.parse(text)

Parse additional WebIDL text. All parsed constructs will be appended to the 'constructs' attribute.

Parser.reset()

Clears all stored constructs.

Parser.find(name)

Return a named construct. If a single name is provided, a breadth-first search through all parsed constructs is performed. Alternatively, a path (names separated by "/" or ".") may be passed to target the search more narrowly. e.g.: find("Foo/bar/baz") looks for an Attribute 'baz', inside a Method 'bar', inside an Interface 'Foo'.

Parser.find_all(name)

Return a list of named constructs. Accepts the same search paths as Parser.find(name).

Parser.normalized_method_name(name [, interface_name=None])

Provide a normalized version of a method name, including the names of all arguments, e.g. "drawCircle(long x, long y, long radius)" becomes: "drawCircle(x, y, radius)". If a valid set of arguments is passed, the passed argument names will be returned in the normalized form. Otherwise, a search is performed for a matching previously parsed method name. The search may be narrowed to a particular interface by passing the name fo the interface or callbak in interface_name.

Parser.normalized_method_names(name [, interface_name=None])

Return a list of all possible normalized names for the method. If the method has optional arguments, the list will contain all possible argument variants. The first item in the list will always be the value returned from normalized_method_name.

Parser.markup(marker)

Returns a marked-up version of the WebIDL input text. The passed 'marker' object will get called back to markup individual elements of the WebIDL. See the Markup section for mroe detail.

Constructs

All Constructs accessed from the parser's Parser.constructs attribute or returned from the parser's find() method are subclasses of the Construct class. The base class provides the following:

Construct.name

The name of the construct.

Construct.idl_type

Contains a string indicating the type of the construct. Possible values are: "const", "enum", "typedef", "interface", "constructor", "attribute", "iterable", "maplike", "setlike", "stringifier", "serializer", "method", "argument", "dictionary", "dict-member", "callback", "implements", "extended-attribute", and "unknown".

Construct.full_name

The name of the construct and all of its parents in path form, e.g.: 'Interface/method_name(argument)/argument'.

Construct.method_name

For 'method' Constructs, contains the normalized method name, otherwise None.

Construct.method_names

For 'method' Constructs, contains the list of all possible normalized method names, otherwise None. Methods have multiple possible normalized names if they contain optional arguments or are variadic.

Construct.normal_name

For 'method' Constructs, contains the normalized method name, otherwise the name of the construct.

Construct.parent

The parent construct, or None if it is a top-level Construct in the source WebIDL.

Construct.extended_attributes

A list of extended attributes, or None. Extended attributes are stored as Constructs, those of the forms: 'identifier', 'identifier=identifier', 'identifier(ArgumentList)', 'identifier=identifier(ArgumentList)', or 'identifier(Type,Type)' are parsed. The first identifier is stored in 'Construct.attribute', the second, if present, is stored in 'Construct.name', arguments are stored in 'Construct.arguments'. Extended attributes not mathing those five forms contain a list of tokens in 'Construct.tokens' and their name is set to 'None'.

Construct.constructors

A list of any extended attributes matching the Constructor or NamedConstructor form. Any constructors present will be prepended to the 'members' attribute of an 'interface' Construct.

Construct.complexity_factor

An index of the complexity of the construct. See Parser.complexity_factor.

Construct.find_member(name)

Find a member of the construct. For 'callback' Constructs with an interface, will search the interface.

Construct.find_members(name)

Return a list of members of the construct matching the name. For 'callback' Constructs with an interface, will search the interface.

Construct.find_method(name)

Find a method within the construct.

Construct.find_methods(name)

Return a list of methods within the construct matching the name.

Construct.find_argument(name[, search_members=True])

Find an argument within the construct. If 'search_members' is true, all members will be searched as well. This allows distinguishing between arguments of a callback versus arguments of a callback interface's methods.

Construct.find_arguments(name[, search_members=True])

Return a list of arguments within the construct mathcing the name. If 'search_members' is true, all members will be searched as well. This allows distinguishing between arguments of a callback versus arguments of a callback interface's methods.

Construct.markup(marker)

Returns a marked-up version of the Constructs's WebIDL source text. See Parser.markup(marker) for information.

Construct Subclasses

Each Construct will be an instance of a Construct subclass corresponding to its 'Construct.idl_type'. Specific subclasses provide the following additional attributes:

Const.type

The Type Production of the Const.

Const.value

The ConstValue Production of the Const.

Enum.values

The EnumValueList Production of the Enum.

Typedef.type

The Type Production of the Typedef.

Argument.type

The Type Production of the Argument.

Argument.variadic

The Symbol "variadic" or 'None'.

Argument.optional

The Symbol "optional" or 'None'.

Argument.default

The Default Production of the Argument or 'None'.

InterfaceMember.member

One of the following Constructs or Productions: Const, Serializer, Stringifier, StaticMember, Iterable, Maplike, Setlike, Attribute, SpecialOperation, or Operation.

InterfaceMember.arguments

Contains a list of any arguments present or 'None'.

Interface.partial

The Symbol "partial" or 'None'.

Interface.inheritance

The Inheritance Production of the Interface or 'None'.

Interface.members

A list of InterfaceMembers.

DictionaryMember.type

The Type Production of the DictionaryMember.

DictionaryMember.default

The Default Production of the DictionaryMember or 'None'.

Dictionary.inheritance

The Inheritance Production of the Dictionary or 'None'.

Dictionary.members

A list of DictionaryMembers.

Callback.return_type

The ReturnType Production of the Callback.

Callback.arguments

Contains a list of any arguments present or 'None' for interface callbacks.

Callback.interface

The 'interface' Construct of the callback, or 'None' for function callbacks.

ImplementsStatement.implements

A string of the type implemented in the ImplementsStatement.

ExtendedAttribute.attribute

The ExtendedAttribute sub-type Production of an ExtendedAttribute. See below. Each of the below ExtendedAttribute sub-type also has an '.attribute' attribute designating the first identifier in the ExtendedAttribute. ExtendedAttributes other than Constructor or NamedConstructor types will also contain this identifier in the '.name' attribute.

ExtendedAttributeArgList.arguments.

Contains a list of any arguments present or 'None'.

ExtendedAttributeIdent.value

Contains a string of the identifier present after the "=".

ExtendedAttributeNamedArgList.value

Contains a string of the identifier present after the "=".

ExtendedAttributeNamedArgList.arguments

Contains a list of any arguments present or 'None'.

ExtendedAttributeTypePair.key_type

The first Type Production of the pair.

ExtendedAttributeTypePair.value_type

The second Type Production of the pair.

ExtendedAttributeUnknown.tokens

Contains a list of tokens in ExtendedAttributes not matching one of the five basic types.

SyntaxError.tokens

Contains a list of tokens that did not match the WebIDL grammar.

Markup

When calling the parser's 'markup(marker)' method, the passed 'marker' is an object that will get called to help generate the markup for each construct, several productions, and to encode the raw text. Markup and encode calls will happen in source order, the text will be split at markup boundaries. The markup methods will be passed the plain text content of the construct or primitive and the construct object in question. Each method must return a tuple of two values (string or None), the prefix and suffix to be injected into the resultant markup surrounding the construct or production. Implementation of all markup methods are optional.

markup_construct(text, construct)

Will be called for each construct.

markup_name(text, construct)

Will be called once per construct with the name of the construct.

markup_type(text, construct)

Will be called for each Type prododuction. Note that types may be nested e.g. unions, sequences, etc.

markup_primitive_type(text, construct)

Will be called for each PrimitiveType production within a Type, e.g. "unsigned long long", "float", "boolean", etc.

markup_buffer_type(text, construct)

Will be called for each BufferRelatedType production witin a Type, e.g. "ArrayBuffer", "DataView", "Int8Array", etc.

markup_string_type(text, construct)

Will be called for each StringType production within a Type, e.g. "ByteString", "DOMString", or "USVString".

markup_object_type(text, construct)

Will be called for each ObjectType production within a Type, e.g. "object" or "Error".

markup_type_name(text, construct)

Will be called when user defined type names are referenced.

markup_keyword(text, construct)

Will be called for each keyword.

markup_enum_value(text, construct)

Will be called for each value in an enum declaration.

encode(text)

Will be called to encode each text run.

Notes

The parser itself is iterable and indexable. Top-level constructs can be tested by the 'in' operator and retrieved by name or index via []. The str() function can also be used on the parser to re-serialize the parsed WebIDL. The serialized output is nullipotent, i.e. str(parser.Parser(text)) == text

Constructs are also iterable and indexable to access members. Additionally constructs can be re-serialized as valid WebIDL via the str() function.

All other WebIDL input is stored in the various constructs as Production objects. Refer to the productions.py source file for details. Productions can be re-serialized as their source WebIDL via the str() function.

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