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fix: refactor/correct calculation of week-view event start/end times (#3947)

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* fix: use DST-friendly tz calculation for TimeSlot end times

Around DST changes, localize(time + duration).astimezone() is not
the same as localize(time).astimezone() + duration. The latter allows
tz-aware times to do their magic and give correct clock times.

* fix: refactor/correct calculation of week-view event start/end times

There were bugs in the timestamp calculations around DST switchover.
This corrects those and tries to clarify and improve documentation in
the relevant code.
This commit is contained in:
Jennifer Richards 2022-05-11 18:08:47 -03:00 committed by GitHub
parent 636ebd7c81
commit cb996c5c0b
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 80 additions and 54 deletions
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23
ietf/meeting/models.py
View file

@ -622,30 +622,29 @@ class TimeSlot(models.Model):
return self.tz().tzname(self.time)
else:
return ""
def utc_start_time(self):
if self.tz():
local_start_time = self.tz().localize(self.time)
return local_start_time.astimezone(pytz.utc)
else:
return None
def utc_end_time(self):
if self.tz():
local_end_time = self.tz().localize(self.end_time())
return local_end_time.astimezone(pytz.utc)
else:
return None
utc_start = self.utc_start_time()
# Add duration after converting start time, otherwise errors creep in around DST change
return None if utc_start is None else utc_start + self.duration
def local_start_time(self):
if self.tz():
local_start_time = self.tz().localize(self.time)
return local_start_time
return self.tz().localize(self.time)
else:
return None
def local_end_time(self):
if self.tz():
local_end_time = self.tz().localize(self.end_time())
return local_end_time
else:
return None
local_start = self.local_start_time()
# Add duration after converting start time, otherwise errors creep in around DST change
return None if local_start is None else local_start + self.duration
@property
def js_identifier(self):

111
ietf/static/js/week-view.js
View file

@ -58,6 +58,7 @@ function compute_swimlanes(items) {
si < items.length &&
start_map[si].start_time < end_map[ei].end_time) {
overlap++;
// Set item.lane - the lane in which it is located (cf. item.lanes)
if (next_lane.length > 0) {
items[start_map[si].index].lane = next_lane.shift();
} else {
@ -81,6 +82,7 @@ function compute_swimlanes(items) {
ei++;
}
if (overlap == 0) {
// set item.lanes - the number of lanes it covers when expanded (cf. item.lane)
for (var i = start_overlap; i < si; i++) {
items[start_map[i].index].lanes = max_lanes;
}
@ -507,7 +509,16 @@ function get_first_item(items, type) {
//===========================================================================
//
window.prepare_items = function (items, timezone_name) {
function make_display_item(item) {
/**
* @param item item to render
* @param day day of meeting
* @param start_time starting time in minutes since start-of-day
* @param duration duration in minutes
* @param formatted_time time label for rendered event
* @param dayname day name label for rendered event
* @returns {{area, end_time: *, type, agenda, room, start_time, dayname, name, time, filter_keywords: ([string]|*), day, key, group}}
*/
function make_display_item(item, day, start_time, duration, formatted_time, dayname) {
return {
name: item.name,
group: item.group,
@ -516,9 +527,14 @@ window.prepare_items = function (items, timezone_name) {
agenda: item.agenda,
key: item.key,
type: item.type,
filter_keywords: item.filter_keywords
filter_keywords: item.filter_keywords,
day: day,
start_time: start_time,
end_time: start_time + duration,
time: formatted_time,
dayname: dayname
}
};
}
/* Ported from Django view, which had the following comment:
* Only show assignments from the traditional meeting "week" (Sat-Fri).
@ -564,46 +580,57 @@ window.prepare_items = function (items, timezone_name) {
var start_day = start_moment.diff(saturday_before, 'days') - 1; // shift so sunday = 0
var end_day = just_before_end_moment.diff(saturday_before, 'days') - 1; // shift so sunday = 0
// Generate display items - create multiple if item ends on different day than starts
for (var day = start_day; day <= end_day; day++) {
var display_item = make_display_item(this_item);
display_item.day = day;
if (day === start_day) {
// First day of session - compute start time
display_item.start_time = start_moment.diff(
start_moment.clone()
.startOf('day'),
'minutes'
);
} else {
// Not first day, start at midnight
display_item.start_time = 0;
display_item.name += " - continued";
/* Generate display item or items
*
* Around DST switchover, days may be 23 or 25 hours long instead of 24 hours, and events
* may end at a clock time that is before they started. To prevent problems, do not do
* direct math between start_moment and end_moment.
*/
const formatted_time = start_moment.format('HHmm') + '-' + end_moment.format('HHmm');
const dayname = start_moment.format('dddd, ')
.toUpperCase() +
start_moment.format('MMMM D, Y');
if (start_day === end_day) {
// one day - add a single display item
const start_of_day = start_moment.clone().startOf('day');
display_items.push(make_display_item(
this_item,
start_day,
start_moment.diff(start_of_day, 'minutes'),
this_item.duration / 60,
formatted_time,
dayname
));
} else {
// split across days - add multiple items
for (var day = start_day; day <= end_day; day++) {
let start_time;
let duration;
if (day === start_day) {
// First day of session - start at correct start time position
const start_of_day = start_moment.clone().startOf('day');
const end_of_day = start_moment.clone().endOf('day');
start_time = start_moment.diff(start_of_day, 'minutes');
duration = end_of_day.diff(start_moment, 'minutes');
} else {
// Not the first day of session
const start_of_day = just_before_end_moment.clone().startOf('day');
start_time = 0;
if (day === end_day) {
// Last day of session - end at correct end time position
duration = just_before_end_moment.diff(start_of_day, 'minutes');
} else {
// Not the last day of the session - end at the end of the day
const end_of_day = just_before_end_moment.clone().endOf('day');
duration = end_of_day.clone().diff(start_of_day, 'minutes');
}
}
const display_item = make_display_item(this_item, day, start_time, duration, formatted_time, dayname);
if (day !== start_day) {
display_item.name += " - continued";
}
display_items.push(display_item);
}
if (day === end_day) {
// Last day of session - compute end time
display_item.end_time = end_moment.diff(
just_before_end_moment.clone()
.startOf('day'),
'minutes'
);
} else {
/* Not last day, use full day. Calculate this on the fly to account for
* daylight savings shifts, when a calendar day is not 24*60 minutes long. */
display_item.end_time = just_before_end_moment.clone()
.endOf('day')
.diff(
just_before_end_moment.clone()
.startOf('day'),
'minutes'
);
}
display_item.time = start_moment.format('HHmm') + '-' + end_moment.format('HHmm');
display_item.dayname = start_moment.format('dddd, ')
.toUpperCase() +
start_moment.format('MMMM D, Y');
display_items.push(display_item);
}
}
return display_items;