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Avoid repeated conversions when shifting Calendar.ISO times #15925

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Merged
josevalim merged 1 commit into from
Sep 22, 2026
+56 −49
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Avoid repeated conversions when shifting Calendar.ISO times #15925

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28 changes: 11 additions & 17 deletions lib/elixir/lib/calendar/iso.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -1923,18 +1923,14 @@ defmodule Calendar.ISO do
@spec shift_time(hour, minute, second, microsecond, Duration.t()) ::
{hour, minute, second, microsecond}
def shift_time(hour, minute, second, microsecond, duration) do
shift_options = shift_time_options(duration)
case duration_to_seconds_and_microseconds(duration) do
{0, {0, _}} ->
{hour, minute, second, microsecond}

Enum.reduce(shift_options, {hour, minute, second, microsecond}, fn
{:microsecond, {0, _}}, time ->
time

{_, 0}, time ->
time

{time_unit, value}, time ->
shift_time_unit(time, value, time_unit)
end)
{seconds, shift_microsecond} ->
time = {hour, minute, second + seconds, microsecond}
shift_time_unit(time, shift_microsecond, :microsecond)
end
end

@doc false
Expand Down Expand Up @@ -2039,7 +2035,8 @@ defmodule Calendar.ISO do
}
end

defp shift_time_options(%Duration{
@compile {:inline, duration_to_seconds_and_microseconds: 1}
defp duration_to_seconds_and_microseconds(%Duration{
year: 0,
month: 0,
week: 0,
Expand All @@ -2049,13 +2046,10 @@ defmodule Calendar.ISO do
second: second,
microsecond: microsecond
}) do
[
second: hour * 3600 + minute * 60 + second,
microsecond: microsecond
]
{(hour * 60 + minute) * 60 + second, microsecond}
end

defp shift_time_options(_duration) do
defp duration_to_seconds_and_microseconds(_duration) do
raise ArgumentError,
"cannot shift time by date scale unit. Expected :hour, :minute, :second, :microsecond"
end
Expand Down
77 changes: 45 additions & 32 deletions lib/elixir/test/elixir/calendar/iso_test.exs
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Original file line number Diff line number Diff line change
Expand Up @@ -650,49 +650,62 @@ defmodule Calendar.ISOTest do
end
end

test "shift_time/2" do
assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(hour: 1)) == {1, 0, 0, {0, 0}}
assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(hour: -1)) == {23, 0, 0, {0, 0}}
describe "shift_time/5" do
test "shifts by duration" do
assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(hour: 1)) == {1, 0, 0, {0, 0}}

assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(hour: -1)) ==
{23, 0, 0, {0, 0}}

assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(minute: 30)) ==
{0, 30, 0, {0, 0}}
assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(minute: 30)) ==
{0, 30, 0, {0, 0}}

assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(minute: -30)) ==
{23, 30, 0, {0, 0}}
assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(minute: -30)) ==
{23, 30, 0, {0, 0}}

assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(second: 30)) ==
{0, 0, 30, {0, 0}}
assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(second: 30)) ==
{0, 0, 30, {0, 0}}

assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(second: -30)) ==
{23, 59, 30, {0, 0}}
assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(second: -30)) ==
{23, 59, 30, {0, 0}}

assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(microsecond: {100, 6})) ==
{0, 0, 0, {100, 6}}
assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(microsecond: {100, 6})) ==
{0, 0, 0, {100, 6}}

assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(microsecond: {-100, 6})) ==
{23, 59, 59, {999_900, 6}}
assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(microsecond: {-100, 6})) ==
{23, 59, 59, {999_900, 6}}

assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(microsecond: {2000, 4})) ==
{0, 0, 0, {2000, 4}}
assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(microsecond: {2000, 4})) ==
{0, 0, 0, {2000, 4}}

assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(microsecond: {-2000, 4})) ==
{23, 59, 59, {998_000, 4}}
assert Calendar.ISO.shift_time(0, 0, 0, {0, 0}, Duration.new!(microsecond: {-2000, 4})) ==
{23, 59, 59, {998_000, 4}}

assert Calendar.ISO.shift_time(0, 0, 0, {3500, 6}, Duration.new!(microsecond: {-2000, 4})) ==
{0, 0, 0, {1500, 4}}
assert Calendar.ISO.shift_time(0, 0, 0, {3500, 6}, Duration.new!(microsecond: {-2000, 4})) ==
{0, 0, 0, {1500, 4}}

assert Calendar.ISO.shift_time(0, 0, 0, {3500, 4}, Duration.new!(minute: 5)) ==
{0, 5, 0, {3500, 4}}
assert Calendar.ISO.shift_time(0, 0, 0, {3500, 4}, Duration.new!(minute: 5)) ==
{0, 5, 0, {3500, 4}}

assert Calendar.ISO.shift_time(0, 0, 0, {3500, 6}, Duration.new!(hour: 4)) ==
{4, 0, 0, {3500, 6}}
assert Calendar.ISO.shift_time(0, 0, 0, {3500, 6}, Duration.new!(hour: 4)) ==
{4, 0, 0, {3500, 6}}

assert Calendar.ISO.shift_time(
23,
59,
59,
{999_900, 6},
Duration.new!(hour: 4, microsecond: {100, 6})
) == {4, 0, 0, {0, 6}}
assert Calendar.ISO.shift_time(
23,
59,
59,
{999_900, 6},
Duration.new!(hour: 4, microsecond: {100, 6})
) == {4, 0, 0, {0, 6}}
end

test "updates precision when time shifts cancel" do
for second <- [-1, 1], precision <- [2, 6] do
duration = Duration.new!(second: second, microsecond: {-second * 1_000_000, precision})

assert Calendar.ISO.shift_time(12, 0, 0, {120_000, 3}, duration) ==
{12, 0, 0, {120_000, precision}}
end
end
end
end
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