make date format supports locale (#6306)

* add --locale flag to make output support locale

* implement again based on nu-utils get_system_locale_string

* add comment

crates/nu-command/Cargo.toml

@@ -33,7 +33,7 @@ base64 = "0.13.0"
 byteorder = "1.4.3"
 bytesize = "1.1.0"
 calamine = "0.18.0"
-chrono = { version = "0.4.21", features = ["serde"] }
+chrono = { version = "0.4.21", features = ["serde", "unstable-locales"] }
 chrono-humanize = "0.2.1"
 chrono-tz = "0.6.3"
 crossterm = "0.24.0"

crates/nu-command/src/date/format.rs

@@ -1,5 +1,4 @@
-use chrono::Local;
-use chrono::{DateTime, TimeZone};
+use chrono::{DateTime, Local, Locale, TimeZone};
 
 use nu_engine::CallExt;
 use nu_protocol::{
@@ -7,6 +6,7 @@ use nu_protocol::{
     engine::{Command, EngineState, Stack},
     Category, Example, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape, Value,
 };
+use nu_utils::locale::get_system_locale_string;
 use std::fmt::{Display, Write};
 
 use super::utils::parse_date_from_string;
@@ -98,7 +98,13 @@ where
     Tz::Offset: Display,
 {
     let mut formatter_buf = String::new();
-    let format = date_time.format(formatter);
+    let locale: Locale = get_system_locale_string()
+        .map(|l| l.replace('-', "_")) // `chrono::Locale` needs something like `xx_xx`, rather than `xx-xx`
+        .unwrap_or_else(|| String::from("en_US"))
+        .as_str()
+        .try_into()
+        .unwrap_or(Locale::en_US);
+    let format = date_time.format_localized(formatter, locale);
 
     match formatter_buf.write_fmt(format_args!("{}", format)) {
         Ok(_) => Value::String {

crates/nu-command/tests/commands/date/format.rs

@@ -12,3 +12,66 @@ fn formatter_not_valid() {
 
     assert!(actual.err.contains("invalid format"));
 }
+
+#[test]
+fn locale_format_respect_different_locale() {
+    let actual = nu!(
+        locale: "en_US",
+        pipeline(
+            r#"
+            "2021-10-22 20:00:12 +01:00" | date format "%c"
+            "#
+        )
+    );
+    assert!(actual.out.contains("Fri 22 Oct 2021 08:00:12 PM +01:00"));
+
+    let actual = nu!(
+        locale: "en_GB",
+        pipeline(
+            r#"
+            "2021-10-22 20:00:12 +01:00" | date format "%c"
+            "#
+        )
+    );
+    assert!(actual.out.contains("Fri 22 Oct 2021 20:00:12 +01:00"));
+
+    let actual = nu!(
+        locale: "de_DE",
+        pipeline(
+            r#"
+            "2021-10-22 20:00:12 +01:00" | date format "%c"
+            "#
+        )
+    );
+    assert!(actual.out.contains("Fr 22 Okt 2021 20:00:12 +01:00"));
+
+    let actual = nu!(
+        locale: "zh_CN",
+        pipeline(
+            r#"
+            "2021-10-22 20:00:12 +01:00" | date format "%c"
+            "#
+        )
+    );
+    assert!(actual.out.contains("2021年10月22日 星期五 20时00分12秒"));
+
+    let actual = nu!(
+        locale: "ja_JP",
+        pipeline(
+            r#"
+            "2021-10-22 20:00:12 +01:00" | date format "%c"
+            "#
+        )
+    );
+    assert!(actual.out.contains("2021年10月22日 20時00分12秒"));
+
+    let actual = nu!(
+        locale: "fr_FR",
+        pipeline(
+            r#"
+            "2021-10-22 20:00:12 +01:00" | date format "%c"
+            "#
+        )
+    );
+    assert!(actual.out.contains("ven. 22 oct. 2021 20:00:12 +01:00"));
+}

crates/nu-utils/src/locale.rs

@@ -27,13 +27,13 @@ pub fn get_system_locale() -> Locale {
 }
 
 #[cfg(debug_assertions)]
-fn get_system_locale_string() -> Option<String> {
+pub fn get_system_locale_string() -> Option<String> {
     std::env::var(LOCALE_OVERRIDE_ENV_VAR)
         .ok()
         .or_else(sys_locale::get_locale)
 }
 
 #[cfg(not(debug_assertions))]
-fn get_system_locale_string() -> Option<String> {
+pub fn get_system_locale_string() -> Option<String> {
     sys_locale::get_locale()
 }