Source code for rdflib.plugins.sparql.results.tsvresults

"""
This implements the Tab Separated SPARQL Result Format

It is implemented with pyparsing, reusing the elements from the SPARQL Parser
"""

import codecs

from pyparsing import (
    FollowedBy,
    LineEnd,
    Literal,
    Optional,
    ParserElement,
    Suppress,
    ZeroOrMore,
)

from rdflib import Literal as RDFLiteral
from rdflib.plugins.sparql.parser import (
    BLANK_NODE_LABEL,
    IRIREF,
    LANGTAG,
    STRING_LITERAL1,
    STRING_LITERAL2,
    BooleanLiteral,
    NumericLiteral,
    Var,
)
from rdflib.plugins.sparql.parserutils import Comp, CompValue, Param
from rdflib.query import Result, ResultParser

ParserElement.setDefaultWhitespaceChars(" \n")


String = STRING_LITERAL1 | STRING_LITERAL2

RDFLITERAL = Comp(
    "literal",
    Param("string", String)
    + Optional(
        Param("lang", LANGTAG.leaveWhitespace())
        | Literal("^^").leaveWhitespace() + Param("datatype", IRIREF).leaveWhitespace()
    ),
)

NONE_VALUE = object()

EMPTY = FollowedBy(LineEnd()) | FollowedBy("\t")
EMPTY.setParseAction(lambda x: NONE_VALUE)

TERM = RDFLITERAL | IRIREF | BLANK_NODE_LABEL | NumericLiteral | BooleanLiteral

ROW = (EMPTY | TERM) + ZeroOrMore(Suppress("\t") + (EMPTY | TERM))
ROW.parseWithTabs()

HEADER = Var + ZeroOrMore(Suppress("\t") + Var)
HEADER.parseWithTabs()


class TSVResultParser(ResultParser):
    def parse(self, source, content_type=None):

        if isinstance(source.read(0), bytes):
            # if reading from source returns bytes do utf-8 decoding
            source = codecs.getreader("utf-8")(source)

        r = Result("SELECT")

        header = source.readline()

        r.vars = list(HEADER.parseString(header.strip(), parseAll=True))
        r.bindings = []
        while True:
            line = source.readline()
            if not line:
                break
            line = line.strip("\n")
            if line == "":
                continue

            row = ROW.parseString(line, parseAll=True)
            r.bindings.append(dict(zip(r.vars, (self.convertTerm(x) for x in row))))

        return r

    def convertTerm(self, t):
        if t is NONE_VALUE:
            return None
        if isinstance(t, CompValue):
            if t.name == "literal":
                return RDFLiteral(t.string, lang=t.lang, datatype=t.datatype)
            else:
                raise Exception("I dont know how to handle this: %s" % (t,))
        else:
            return t