Content line parameter parsing doesn't support quoted parameter values

[praichor]

The function ics.parse.ContentLine.parse doesn't support quoted parameters as specified in https://tools.ietf.org/html/rfc5545#page-8.
This causes trouble for example for some calendars from Outlook.

Possible solution, which did it for me:

@classmethod
def parse(cls, line):
    idx = 0
    # Parse key and parameters:
    while idx < len(line) and line[idx] != ':':
        # Parse key:
        while idx < len(line) and line[idx] not in ':;':
            idx += 1
        name = line[:idx]
        params = {}
        # Parse parameters:
        while line[idx] == ';':
            idx += 1
            paramname = ''
            # Parse parameter name:
            while idx < len(line) and line[idx] != '=':
                paramname += line[idx]
                idx += 1
            # Parse parameter values:
            if line[idx] != '=':
                raise ParseError("No '=' in line '{}'".format(paramstr))
            idx += 1
            paramvals = []
            while True:
                # Parse single parameter:
                paramval = ''
                if line[idx] == '"':
                    idx += 1
                    while idx < len(line) and line[idx] != '"':
                        paramval += line[idx]
                        idx += 1
                    idx += 1
                else:
                    while idx < len(line) and line[idx] not in ':;,':
                        paramval += line[idx]
                        idx += 1
                paramvals.append(paramval)
                if line[idx] != ',':
                    break
                idx += 1
            params[paramname] = paramvals
    # Parse value:
    if line[idx] != ':':
        raise ParseError("No ':' in line '{}'".format(line))
    idx += 1
    value = line[idx:].strip()
    return cls(name, params, value)

[C4ptainCrunch]

Hi @praichor !
Thank you for reporting this issue. Could you support a minimal file that i could use to reproduce it ?

[praichor]

Hi @C4ptainCrunch,
Btw, thanks for your great work! In this case it is irreplaceable for importing external calendars into my calendar server.
Reproduction script:

not_working_input = """
BEGIN:VCALENDAR
PRODID:-//Microsoft Corporation//Outlook 16.0 MIMEDIR//EN
VERSION:2.0
METHOD:PUBLISH
X-CALSTART:20190103T230000Z
X-CALEND:20191219T230000Z
X-WR-RELCALID:{0000002E-0702-2B5E-B8A1-8E52149384CE}
X-WR-CALNAME:JPL2019
BEGIN:VTIMEZONE
TZID:W. Europe Standard Time
BEGIN:STANDARD
DTSTART:16011028T030000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:16010325T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
CATEGORIES:Test
CLASS:PRIVATE
CREATED:20181209T181307Z
DTEND;TZID="W. Europe Standard Time":20190107T000000
DTSTAMP:20181209T182521Z
DTSTART;TZID="W. Europe Standard Time":20190104T000000
LAST-MODIFIED:20181209T181307Z
LOCATION:Test
PRIORITY:5
SEQUENCE:0
SUMMARY:Test
TRANSP:TRANSPARENT
UID:AAAAAA7yqOF4pKxDnjNcS1lZa4oHAP1tU+LVLl5KjQnKvp6K2xgAAAAAAj8AANs0z1XS86d
	DlPhJenbJRzoAAAAAngAAAA==
X-MICROSOFT-CDO-BUSYSTATUS:FREE
X-MICROSOFT-CDO-IMPORTANCE:1
END:VEVENT
END:VCALENDAR
"""

working_input = not_working_input.replace('"W. Europe Standard Time"', 'W. Europe Standard Time')

import ics

# Time zone of the event is correctly linked to the time zone definition VTIMEZONE:
working_cal = ics.Calendar(working_input)
print(list(working_cal.events)[0].begin)

# Time zone of the event is not linked to the time zone definition VTIMEZONE,
# because the quotation marks around the time zone in the event are not removed
# as they should be, and therefore the time zone lookup fails:
not_working_cal = ics.Calendar(not_working_input)
print(list(not_working_cal.events)[0].begin)

[C4ptainCrunch]

Also see #193

[praichor]

Also see #193

What about the following to also cover #193? Adding

                        if line[idx] == '\\':
                            idx += 1

at two places. New full function:

@classmethod`
def parse(cls, line):
    idx = 0
    # Parse key and parameters:
    while idx < len(line) and line[idx] != ':':
        # Parse key:
        while idx < len(line) and line[idx] not in ':;':
            idx += 1
        name = line[:idx]
        params = {}
        # Parse parameters:
        while line[idx] == ';':
            idx += 1
            paramname = ''
            # Parse parameter name:
            while idx < len(line) and line[idx] != '=':
                paramname += line[idx]
                idx += 1
            # Parse parameter values:
            if line[idx] != '=':
                raise ParseError("No '=' in line '{}'".format(paramstr))
            idx += 1
            paramvals = []
            while True:
                # Parse single parameter:
                paramval = ''
                if line[idx] == '"':
                    idx += 1
                    while idx < len(line) and line[idx] != '"':
                        if line[idx] == '\\':
                            idx += 1
                        paramval += line[idx]
                        idx += 1
                    idx += 1
                else:
                    while idx < len(line) and line[idx] not in ':;,':
                        if line[idx] == '\\':
                            idx += 1
                        paramval += line[idx]
                        idx += 1
                paramvals.append(paramval)
                if line[idx] != ',':
                    break
                idx += 1
            params[paramname] = paramvals
    # Parse value:
    if line[idx] != ':':
        raise ParseError("No ':' in line '{}'".format(line))
    idx += 1
    value = line[idx:].strip()
    return cls(name, params, value)

[C4ptainCrunch]

I'm working on a branch that uses a formal grammar (see grammar.ebnf) that solves both issues.

This is still an experiment, but working with a real parser looks like the way to go.

[praichor]

Using Tatsu looks like a good choice!
Thanks for the fix!