parse most common date formats using dtparse crate (#2303)

* use dtparse crate to parse most common date formats

* use dtparse crate to parse most common date formats - cargo fmt

crates/nu-cli/Cargo.toml

@@ -34,8 +34,9 @@ codespan-reporting = "0.9.5"
 csv = "1.1"
 ctrlc = {version = "3.1.4", optional = true}
 derive-new = "0.5.8"
-directories = {version = "2.0.2", optional = true} 
+directories = {version = "2.0.2", optional = true}
 dirs = {version = "2.0.2", optional = true}
+dtparse = "1.1.0"
 dunce = "1.0.1"
 eml-parser = "0.1.0"
 filesize = "0.2.0"

crates/nu-cli/src/commands/str_/to_datetime.rs

@@ -8,7 +8,7 @@ use nu_protocol::{
 use nu_source::{Tag, Tagged};
 use nu_value_ext::ValueExt;
 
-use chrono::DateTime;
+use chrono::{DateTime, FixedOffset, LocalResult, Offset, TimeZone};
 
 #[derive(Deserialize)]
 struct Arguments {
@@ -51,11 +51,23 @@ impl WholeStreamCommand for SubCommand {
     }
 
     fn examples(&self) -> Vec<Example> {
-        vec![Example {
-            description: "Convert to datetime",
-            example: "echo '16.11.1984 8:00 am +0000' | str to-datetime",
-            result: None,
-        }]
+        vec![
+            Example {
+                description: "Convert to datetime",
+                example: "echo '16.11.1984 8:00 am +0000' | str to-datetime",
+                result: None,
+            },
+            Example {
+                description: "Convert to datetime",
+                example: "echo '2020-08-04T16:39:18+00:00' | str to-datetime",
+                result: None,
+            },
+            Example {
+                description: "Convert to datetime using a custom format",
+                example: "echo '20200904_163918+0000' | str to-datetime -f '%Y%m%d_%H%M%S%z'",
+                result: None,
+            },
+        ]
     }
 }
 
@@ -73,9 +85,9 @@ async fn operate(
     let column_paths: Vec<_> = rest;
 
     let options = if let Some(Tagged { item: fmt, .. }) = format {
-        DatetimeFormat(fmt)
+        Some(DatetimeFormat(fmt))
     } else {
-        DatetimeFormat(String::from("%d.%m.%Y %H:%M %P %z"))
+        None
     };
 
     Ok(input
@@ -102,23 +114,49 @@ async fn operate(
 
 fn action(
     input: &Value,
-    options: &DatetimeFormat,
+    options: &Option<DatetimeFormat>,
     tag: impl Into<Tag>,
 ) -> Result<Value, ShellError> {
     match &input.value {
         UntaggedValue::Primitive(Primitive::Line(s))
         | UntaggedValue::Primitive(Primitive::String(s)) => {
-            let dt = &options.0;
-
-            let out = match DateTime::parse_from_str(s, dt) {
-                Ok(d) => UntaggedValue::date(d),
-                Err(reason) => {
-                    return Err(ShellError::labeled_error(
-                        "could not parse as datetime",
-                        reason.to_string(),
-                        tag.into().span,
-                    ))
-                }
+            let out = match options {
+                Some(dt) => match DateTime::parse_from_str(s, &dt.0) {
+                    Ok(d) => UntaggedValue::date(d),
+                    Err(reason) => {
+                        return Err(ShellError::labeled_error(
+                            format!("could not parse as datetime using format '{}'", dt.0),
+                            reason.to_string(),
+                            tag.into().span,
+                        ))
+                    }
+                },
+                None => match dtparse::parse(s) {
+                    Ok((native_dt, fixed_offset)) => {
+                        let offset = match fixed_offset {
+                            Some(fo) => fo,
+                            None => FixedOffset::east(0).fix(),
+                        };
+                        match offset.from_local_datetime(&native_dt) {
+                            LocalResult::Single(d) => UntaggedValue::date(d),
+                            LocalResult::Ambiguous(d, _) => UntaggedValue::date(d),
+                            LocalResult::None => {
+                                return Err(ShellError::labeled_error(
+                                    "could not convert to a timezone-aware datetime",
+                                    "local time representation is invalid",
+                                    tag.into().span,
+                                ))
+                            }
+                        }
+                    }
+                    Err(reason) => {
+                        return Err(ShellError::labeled_error(
+                            "could not parse as datetime",
+                            reason.to_string(),
+                            tag.into().span,
+                        ))
+                    }
+                },
             };
 
             Ok(out.into_value(tag))
@@ -152,7 +190,7 @@ mod tests {
     fn takes_a_date_format() {
         let date_str = string("16.11.1984 8:00 am +0000");
 
-        let fmt_options = DatetimeFormat("%d.%m.%Y %H:%M %P %z".to_string());
+        let fmt_options = Some(DatetimeFormat("%d.%m.%Y %H:%M %P %z".to_string()));
 
         let actual = action(&date_str, &fmt_options, Tag::unknown()).unwrap();
 
@@ -162,11 +200,21 @@ mod tests {
         }
     }
 
+    #[test]
+    fn takes_iso8601_date_format() {
+        let date_str = string("2020-08-04T16:39:18+00:00");
+        let actual = action(&date_str, &None, Tag::unknown()).unwrap();
+        match actual.value {
+            UntaggedValue::Primitive(Primitive::Date(_)) => {}
+            _ => panic!("Didn't convert to date"),
+        }
+    }
+
     #[test]
     fn communicates_parsing_error_given_an_invalid_datetimelike_string() {
         let date_str = string("16.11.1984 8:00 am Oops0000");
 
-        let fmt_options = DatetimeFormat("%d.%m.%Y %H:%M %P %z".to_string());
+        let fmt_options = Some(DatetimeFormat("%d.%m.%Y %H:%M %P %z".to_string()));
 
         let actual = action(&date_str, &fmt_options, Tag::unknown());