feat: hide serde behind a feature gate

Cargo.toml

@@ -19,7 +19,7 @@ vendored = ["yara-sys/vendored"]
 [dependencies]
 thiserror = "1.0"
 lazy_static = "1.3.0"
-serde = { version = "1.0", features = ["derive"] }
+serde = { version = "1.0", features = ["derive"], optional = true }
 
 [dev-dependencies]
 crossbeam = "0.7"

src/matches.rs

@@ -1,6 +1,9 @@
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+
 /// A match within a scan.
-use serde::{Serialize, Deserialize};
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct Match {
     /// Offset of the match within the scanning area.
     pub offset: usize,

src/rules.rs

@@ -2,8 +2,10 @@ use std::convert::TryFrom;
 use std::fs::File;
 use std::io::{Read, Write};
 use std::path::Path;
+
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
 pub use yara_sys::scan_flags::*;
-use serde::{Serialize, Deserialize};
 
 use crate::{errors::*, initialize::InitializationToken, internals, YrString};
 
@@ -188,7 +190,8 @@ impl Drop for Rules {
 
 /// A rule that matched during a scan.
 
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct Rule<'r> {
     /// Name of the rule.
     pub identifier: &'r str,
@@ -203,14 +206,16 @@ pub struct Rule<'r> {
 }
 
 /// Metadata specified in a rule.
-#[derive(Debug, Eq, PartialEq, Serialize, Deserialize)]
+#[derive(Debug, Eq, PartialEq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct Metadata<'r> {
     pub identifier: &'r str,
     pub value: MetadataValue<'r>,
 }
 
 /// Type of the value in [MetaData](struct.Metadata.html)
-#[derive(Debug, Eq, PartialEq, Serialize, Deserialize)]
+#[derive(Debug, Eq, PartialEq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum MetadataValue<'r> {
     Integer(i64),
     String(&'r str),

src/string.rs

@@ -1,8 +1,10 @@
 use crate::Match;
-use serde::{Serialize, Deserialize};
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
 
 /// A matcher string that matched during a scan.
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub struct YrString<'a> {
     /// Name of the string, with the '$'.
     pub identifier: &'a str,