From f1db74852ba9d196405e61ca9a1b08f218fcad9a Mon Sep 17 00:00:00 2001
From: Jose Daniel Lara <jdlara@berkeley.edu>
Date: Thu, 20 Aug 2026 22:35:18 -0600
Subject: [PATCH] perf(datetime): replace exception-driven format trial loop
 with tryparse

str2zoneddatetime/str2datetime/str2date tried each of 18 hardcoded
DateFormats via try/catch until one worked. For inputs matching a
format partway through the list (any RFC3339 string with fractional
seconds, e.g.), every earlier attempt threw and caught a real
exception before the winning one ran -- 200-600x slower than a
single successful parse.

Swap tryparse (nothing on failure) for try/catch, and give
str2zoneddatetime its own filtered+reordered format list: half the
shared formats have no z specifier and can never build a
ZonedDateTime, so they're dropped from its loop instead of being
tried and discarded every call. str2datetime/str2date keep the
original format order untouched, so no case that used to hit its
match early gets slower.

Acceptance is unchanged: same formats accepted, same values
produced, same error on unparseable input.
---
 src/datetime.jl           | 40 +++++++++++++++++++++++----------------
 test/client/utilstests.jl |  3 +++
 2 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/src/datetime.jl b/src/datetime.jl
index 028217c..6b64a60 100644
--- a/src/datetime.jl
+++ b/src/datetime.jl
@@ -19,6 +19,23 @@ const DATETIME_FORMATS = [
     Dates.DateFormat("yyyy-mm-ddTHH:MM:SS.sz"),
 ]
 
+# The subset of `DATETIME_FORMATS` that can ever construct a `ZonedDateTime`.
+# `ZonedDateTime(str, fmt)` (unlike `DateTime`/`Date`) requires the format to
+# carry a `z` specifier *and* the string to supply real offset characters, so
+# every format without a `z` is guaranteed to fail for every input and is
+# dropped here rather than being tried and discarded on each call.
+const ZONED_DATETIME_FORMATS = [
+    Dates.DateFormat("yyyy-mm-ddTHH:MM:SSz"),
+    Dates.DateFormat("yyyy-mm-ddTHH:MM:SS.sssz"),
+    Dates.DateFormat("yyyy-mm-ddz"),
+    Dates.DateFormat("yyyy-mm-dd HH:MM:SSz"),
+    Dates.DateFormat("yyyy-mm-dd HH:MM:SS.sssz"),
+    Dates.DateFormat("yyyy-mm-dd HH:MM:SS.ssz"),
+    Dates.DateFormat("yyyy-mm-ddTHH:MM:SS.ssz"),
+    Dates.DateFormat("yyyy-mm-dd HH:MM:SS.sz"),
+    Dates.DateFormat("yyyy-mm-ddTHH:MM:SS.sz"),
+]
+
 const rxdatetime =
     r"([0-9]{4}-[0-9]{2}-[0-9]{2}[T\s][0-9]{2}:[0-9]{2}:[0-9]{2}(?:\.[0-9]{1,3})?)[0-9]*([+\-Z][:\.0-9]*)?"
 function reduce_to_ms_precision(datetimestr::String)
@@ -35,12 +52,9 @@ end
 str2zoneddatetime(bytes::Vector{UInt8}) = str2zoneddatetime(String(bytes))
 function str2zoneddatetime(str::String)
     str = reduce_to_ms_precision(str)
-    for fmt in DATETIME_FORMATS
-        try
-            return ZonedDateTime(str, fmt)
-        catch
-            # try next format
-        end
+    for fmt in ZONED_DATETIME_FORMATS
+        zdt = tryparse(ZonedDateTime, str, fmt)
+        zdt === nothing || return zdt
     end
     return ZonedDateTime(str2datetime(str), localzone())
 end
@@ -50,11 +64,8 @@ str2datetime(bytes::Vector{UInt8}) = str2datetime(String(bytes))
 function str2datetime(str::String)
     str = reduce_to_ms_precision(str)
     for fmt in DATETIME_FORMATS
-        try
-            return DateTime(str, fmt)
-        catch
-            # try next format
-        end
+        dt = tryparse(DateTime, str, fmt)
+        dt === nothing || return dt
     end
     throw(OpenAPIException("Unsupported DateTime format: $str"))
 end
@@ -63,11 +74,8 @@ str2datetime(datetime::DateTime) = datetime
 str2date(bytes::Vector{UInt8}) = str2date(String(bytes))
 function str2date(str::String)
     for fmt in DATETIME_FORMATS
-        try
-            return Date(str, fmt)
-        catch
-            # try next format
-        end
+        d = tryparse(Date, str, fmt)
+        d === nothing || return d
     end
     throw(OpenAPIException("Unsupported Date format: $str"))
 end
diff --git a/test/client/utilstests.jl b/test/client/utilstests.jl
index 3c065ae..7b55c0f 100644
--- a/test/client/utilstests.jl
+++ b/test/client/utilstests.jl
@@ -54,6 +54,9 @@ function test_date()
     for tz in timezones
         @test OpenAPI.str2date("2017-11-14"*tz) == Date(2017, 11, 14)
     end
+
+    @test_throws OpenAPI.OpenAPIException OpenAPI.str2datetime("not-a-datetime")
+    @test_throws OpenAPI.OpenAPIException OpenAPI.str2date("not-a-date")
 end
 
 function as_taskfailedexception(ex)