[glib: 3/4] gdatetime: Format iso8601 strings with microsecond precision

[Philip Withnall <pwithnall src gnome org>]

commit 8e13683f70913e234aa89b4a46ccdc0c9432ccf6
Author: Johan Bjäreholt <johanbj axis com>
Date:   Wed Aug 5 13:36:19 2020 +0200

    gdatetime: Format iso8601 strings with microsecond precision

 glib/gdatetime.c       | 10 +++++++++-
 glib/tests/gdatetime.c |  8 ++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)
---
diff --git a/glib/gdatetime.c b/glib/gdatetime.c
index 143815b52..f85afab0c 100644
--- a/glib/gdatetime.c
+++ b/glib/gdatetime.c
@@ -3465,6 +3465,8 @@ g_date_time_format (GDateTime   *datetime,
  * including the date, time and time zone, and return that as a UTF-8 encoded
  * string.
  *
+ * Since GLib 2.66, this will output to sub-second precision if needed.
+ *
  * Returns: (transfer full) (nullable): a newly allocated string formatted in
  *   ISO 8601 format or %NULL in the case that there was an error. The string
  *   should be freed with g_free().
@@ -3477,9 +3479,15 @@ g_date_time_format_iso8601 (GDateTime *datetime)
   GString *outstr = NULL;
   gchar *main_date = NULL;
   gint64 offset;
+  gchar *format = "%Y-%m-%dT%H:%M:%S";
+
+  /* if datetime has sub-second non-zero values below the second precision we
+   * should print them as well */
+  if (datetime->usec % G_TIME_SPAN_SECOND != 0)
+    format = "%Y-%m-%dT%H:%M:%S.%f";
 
   /* Main date and time. */
-  main_date = g_date_time_format (datetime, "%Y-%m-%dT%H:%M:%S");
+  main_date = g_date_time_format (datetime, format);
   outstr = g_string_new (main_date);
   g_free (main_date);
 
diff --git a/glib/tests/gdatetime.c b/glib/tests/gdatetime.c
index 79a446e4b..3e75f4ed2 100644
--- a/glib/tests/gdatetime.c
+++ b/glib/tests/gdatetime.c
@@ -2208,6 +2208,14 @@ test_format_iso8601 (void)
   g_free (p);
   g_date_time_unref (dt);
   g_time_zone_unref (tz);
+
+  tz = g_time_zone_new_utc ();
+  dt = g_date_time_new (tz, 2020, 8, 5, 12, 30, 55.000001);
+  p = g_date_time_format_iso8601 (dt);
+  g_assert_cmpstr (p, ==, "2020-08-05T12:30:55.000001Z");
+  g_free (p);
+  g_date_time_unref (dt);
+  g_time_zone_unref (tz);
 }
 
 #pragma GCC diagnostic push