Python Plugin Design:

The plugin consists of various parts: a parser library, a duchain library and

the actual plugin incorporating code completion and highlighting support

The Parser Library

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The parser is written using the KDevelop-PG Qt parser generator. The standard

Python grammar has been transformed into a grammar that KDevelop-PG can

understand, see parser/python.g. The generated parser parses a piece of python

code and creates an abstract syntax tree from that. This AST is very close to

the actual grammar of the language, which makes it unnecessarily complex in

some places.

Thus the initial AST is transformed, via the AstBuilder class, into a different

AST that has been modelled after the python language reference. This happens

inside the parser library, so users only see this hand-crafted AST structure.

The parsing and AST transformation is driven by the PythonDriver class, which

simply takes some input and runs the parser over it.

The translation of the input text into tokens is done by a handwritten lexer in

the Lexer class. It also handles creation of indentation and dedentation tokens

as needed by the pythong language.

Last but most importantly, there a couple of unit tests for the above parts. In

particular there are a couple of example files to simply test the parser and a

Qt unit test to parse the lexer. The creation of the handcrafted AST is tested

in the rest of the various unittests.

The DUChain Library

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This library builds a Definition-Use-Chain from the AST, which is then used to

support code completion, syntax highlighting and other language features in

KDevelop. The design of the DUChain is described at:

http://api.kde.org/4.x-api/kdevplatform-apidocs/language/html/duchain-design.html

The following language elements create a new Context:

- a class definition

- a function definition

- a compound statement, that includes for, while, if, with statements