Make creating a SrtftimeItems return a Result

src/date.rs

@@ -21,6 +21,7 @@ use crate::naive::{IsoWeek, NaiveDate, NaiveTime};
 use crate::offset::{TimeZone, Utc};
 use crate::time_delta::TimeDelta;
 use crate::DateTime;
+use crate::ParseError;
 use crate::{Datelike, Weekday};
 
 /// ISO 8601 calendar date with time zone.
@@ -329,8 +330,8 @@ where
     #[cfg(any(feature = "alloc", feature = "std", test))]
     #[cfg_attr(docsrs, doc(cfg(any(feature = "alloc", feature = "std"))))]
     #[inline]
-    pub fn format<'a>(&self, fmt: &'a str) -> DelayedFormat<StrftimeItems<'a>> {
-        self.format_with_items(StrftimeItems::new(fmt))
+    pub fn format<'a>(&self, fmt: &'a str) -> Result<DelayedFormat<StrftimeItems<'a>>, ParseError> {
+        Ok(self.format_with_items(StrftimeItems::new(fmt)?))
     }
 
     /// Formats the date with the specified formatting items and locale.
@@ -365,8 +366,8 @@ where
         &self,
         fmt: &'a str,
         locale: Locale,
-    ) -> DelayedFormat<StrftimeItems<'a>> {
-        self.format_localized_with_items(StrftimeItems::new_with_locale(fmt, locale), locale)
+    ) -> Result<DelayedFormat<StrftimeItems<'a>>, ParseError> {
+        Ok(self.format_localized_with_items(StrftimeItems::new_with_locale(fmt, locale)?, locale))
     }
 }
 

src/datetime/mod.rs

@@ -578,7 +578,7 @@ impl DateTime<FixedOffset> {
     /// ```
     pub fn parse_from_str(s: &str, fmt: &str) -> ParseResult<DateTime<FixedOffset>> {
         let mut parsed = Parsed::new();
-        parse(&mut parsed, s, StrftimeItems::new(fmt))?;
+        parse(&mut parsed, s, StrftimeItems::new(fmt)?)?;
         parsed.to_datetime()
     }
 }
@@ -753,14 +753,14 @@ where
     /// use chrono::prelude::*;
     ///
     /// let date_time: DateTime<Utc> = Utc.with_ymd_and_hms(2017, 04, 02, 12, 50, 32).unwrap();
-    /// let formatted = format!("{}", date_time.format("%d/%m/%Y %H:%M"));
+    /// let formatted = format!("{}", date_time.format("%d/%m/%Y %H:%M").unwrap());
     /// assert_eq!(formatted, "02/04/2017 12:50");
     /// ```
     #[cfg(any(feature = "alloc", feature = "std", test))]
     #[cfg_attr(docsrs, doc(cfg(any(feature = "alloc", feature = "std"))))]
     #[inline]
-    pub fn format<'a>(&self, fmt: &'a str) -> DelayedFormat<StrftimeItems<'a>> {
-        self.format_with_items(StrftimeItems::new(fmt))
+    pub fn format<'a>(&self, fmt: &'a str) -> Result<DelayedFormat<StrftimeItems<'a>>, ParseError> {
+        Ok(self.format_with_items(StrftimeItems::new(fmt)?))
     }
 
     /// Formats the combined date and time with the specified formatting items and locale.
@@ -798,8 +798,8 @@ where
         &self,
         fmt: &'a str,
         locale: Locale,
-    ) -> DelayedFormat<StrftimeItems<'a>> {
-        self.format_localized_with_items(StrftimeItems::new_with_locale(fmt, locale), locale)
+    ) -> Result<DelayedFormat<StrftimeItems<'a>>, ParseError> {
+        Ok(self.format_localized_with_items(StrftimeItems::new_with_locale(fmt, locale)?, locale))
     }
 }
 
@@ -1331,3 +1331,8 @@ fn test_decodable_json<FUtc, FFixed, FLocal, E>(
     assert!(utc_from_str(r#""2014-07-32T12:34:06Z""#).is_err());
     assert!(fixed_from_str(r#""2014-07-32T12:34:06Z""#).is_err());
 }
+
+#[test]
+fn test_invalid_format() {
+    assert!(Utc::now().format("%").is_err());
+}

src/datetime/tests.rs

@@ -388,7 +388,10 @@ fn test_to_string_round_trip_with_local() {
 fn test_datetime_format_with_local() {
     // if we are not around the year boundary, local and UTC date should have the same year
     let dt = Local::now().with_month(5).unwrap();
-    assert_eq!(dt.format("%Y").to_string(), dt.with_timezone(&Utc).format("%Y").to_string());
+    assert_eq!(
+        dt.format("%Y").unwrap().to_string(),
+        dt.with_timezone(&Utc).format("%Y").unwrap().to_string()
+    );
 }
 
 #[test]
@@ -579,25 +582,25 @@ fn test_datetime_format_alignment() {
     let datetime = Utc.with_ymd_and_hms(2007, 1, 2, 0, 0, 0).unwrap();
 
     // Item::Literal
-    let percent = datetime.format("%%");
+    let percent = datetime.format("%%").unwrap();
     assert_eq!("  %", format!("{:>3}", percent));
     assert_eq!("%  ", format!("{:<3}", percent));
     assert_eq!(" % ", format!("{:^3}", percent));
 
     // Item::Numeric
-    let year = datetime.format("%Y");
+    let year = datetime.format("%Y").unwrap();
     assert_eq!("  2007", format!("{:>6}", year));
     assert_eq!("2007  ", format!("{:<6}", year));
     assert_eq!(" 2007 ", format!("{:^6}", year));
 
     // Item::Fixed
-    let tz = datetime.format("%Z");
+    let tz = datetime.format("%Z").unwrap();
     assert_eq!("  UTC", format!("{:>5}", tz));
     assert_eq!("UTC  ", format!("{:<5}", tz));
     assert_eq!(" UTC ", format!("{:^5}", tz));
 
     // [Item::Numeric, Item::Space, Item::Literal, Item::Space, Item::Numeric]
-    let ymd = datetime.format("%Y %B %d");
+    let ymd = datetime.format("%Y %B %d").unwrap();
     let ymd_formatted = "2007 January 02";
     assert_eq!(format!("  {}", ymd_formatted), format!("{:>17}", ymd));
     assert_eq!(format!("{}  ", ymd_formatted), format!("{:<17}", ymd));

src/format/mod.rs

@@ -22,7 +22,7 @@
 //!
 //! let date_time = Utc.with_ymd_and_hms(2020, 11, 10, 0, 1, 32).unwrap();
 //!
-//! let formatted = format!("{}", date_time.format("%Y-%m-%d %H:%M:%S"));
+//! let formatted = format!("{}", date_time.format("%Y-%m-%d %H:%M:%S").unwrap());
 //! assert_eq!(formatted, "2020-11-10 00:01:32");
 //!
 //! let parsed = Utc.datetime_from_str(&formatted, "%Y-%m-%d %H:%M:%S")?;

src/format/parse.rs

@@ -895,7 +895,7 @@ fn parse_rfc850() {
     let dt = Utc.with_ymd_and_hms(1994, 11, 6, 8, 49, 37).unwrap();
 
     // Check that the format is what we expect
-    assert_eq!(dt.format(RFC850_FMT).to_string(), dt_str);
+    assert_eq!(dt.format(RFC850_FMT).unwrap().to_string(), dt_str);
 
     // Check that it parses correctly
     assert_eq!(Ok(dt), Utc.datetime_from_str("Sunday, 06-Nov-94 08:49:37 GMT", RFC850_FMT));