Remove lazy_static dependency in favor of std OnceLock

rrule/Cargo.toml

@@ -15,7 +15,6 @@ edition.workspace = true
 [dependencies]
 chrono = "0.4.19"
 chrono-tz = "0.9.0"
-lazy_static = "1.4.0"
 log = "0.4.16"
 regex = { version = "1.5.5", default-features = false, features = ["perf", "std"] }
 clap = { version = "4.1.9", optional = true, features = ["derive"] }

rrule/src/parser/regex.rs

@@ -1,17 +1,11 @@
 //! Utility functions around the regexes we use for parsing rrule strings.
-use std::str::FromStr;
 
-use lazy_static::lazy_static;
+use std::{str::FromStr, sync::OnceLock};
+
 use regex::{Captures, Regex};
 
 use super::{content_line::PropertyName, ParseError};
 
-lazy_static! {
-    static ref DATESTR_RE: Regex =
-        Regex::new(r"(?m)^([0-9]{4})([0-9]{2})([0-9]{2})(T([0-9]{2})([0-9]{2})([0-9]{2})(Z?))?$")
-            .expect("DATESTR_RE regex failed");
-}
-
 #[derive(Debug, PartialEq)]
 pub(crate) struct ParsedDateString {
     pub year: i32,
@@ -50,7 +44,15 @@ impl ParsedDateString {
     /// Parses a date string with format `YYYYMMDD(THHMMSSZ)` where the part in parentheses
     /// is optional. It returns [`ParsedDateString`].
     pub(crate) fn from_ical_datetime(val: &str) -> Result<Self, ParseError> {
+        static DATESTR_RE: OnceLock<Regex> = OnceLock::new();
+
         let captures = DATESTR_RE
+            .get_or_init(|| {
+                Regex::new(
+                    r"(?m)^([0-9]{4})([0-9]{2})([0-9]{2})(T([0-9]{2})([0-9]{2})([0-9]{2})(Z?))?$",
+                )
+                .expect("DATESTR_RE regex failed")
+            })
             .captures(val)
             .ok_or_else(|| ParseError::InvalidDateTimeFormat(val.into()))?;
 
@@ -84,14 +86,14 @@ impl ParsedDateString {
     }
 }
 
-lazy_static! {
-    static ref PARSE_PROPERTY_NAME_RE: Regex =
-        Regex::new(r"(?m)^([A-Z]+?)[:;]").expect("PARSE_PROPERTY_NAME_RE regex failed");
-}
-
 /// Get the line property name, the `RRULE:`, `EXRULE:` etc part.
 pub(crate) fn get_property_name(val: &str) -> Result<Option<PropertyName>, ParseError> {
+    static PARSE_PROPERTY_NAME_RE: OnceLock<Regex> = OnceLock::new();
+
     PARSE_PROPERTY_NAME_RE
+        .get_or_init(|| {
+            Regex::new(r"(?m)^([A-Z]+?)[:;]").expect("PARSE_PROPERTY_NAME_RE regex failed")
+        })
         .captures(val)
         .and_then(|captures| captures.get(1))
         .map(|name| PropertyName::from_str(name.as_str()))