Eliminate syntect library's dependency on serde's "derive" feature

.github/workflows/CI.yml

@@ -33,6 +33,9 @@ jobs:
     - name: Run cargo check
       run: |
         cargo check --all-features --all-targets
+        # Check that if some other crate in the downstream dependency tree
+        # enables serde's "derive" feature, syntect still builds.
+        cargo check --all-features --features serde/derive
 
   documentation:
     name: Documentation checks

Cargo.toml

@@ -28,7 +28,8 @@ plist = { version = "1.3", optional = true }
 bincode = { version = "1.0", optional = true }
 flate2 = { version = "1.0", optional = true }
 fnv = { version = "1.0", optional = true }
-serde = { version = "1.0", features = ["derive"] }
+serde = "1.0"
+serde_derive = "1.0"
 serde_json = "1.0"
 once_cell = "1.8"
 thiserror = "1.0"

src/dumps.rs

@@ -34,7 +34,7 @@ use flate2::bufread::ZlibDecoder;
 #[cfg(feature = "dump-create")]
 use flate2::Compression;
 #[cfg(feature = "dump-create")]
-use serde::Serialize;
+use serde::ser::Serialize;
 #[cfg(feature = "dump-load")]
 use serde::de::DeserializeOwned;
 

src/highlighting/selector.rs

@@ -2,7 +2,7 @@
 /// released under the MIT license by @defuz
 use crate::parsing::{Scope, ScopeStack, MatchPower, ParseScopeError};
 use std::str::FromStr;
-use serde::{Deserialize, Serialize};
+use serde_derive::{Deserialize, Serialize};
 
 /// A single selector consisting of a stack to match and a possible stack to
 /// exclude from being matched.

src/highlighting/style.rs

@@ -1,7 +1,7 @@
 // Code based on [https://github.com/defuz/sublimate/blob/master/src/core/syntax/scope.rs](https://github.com/defuz/sublimate/blob/master/src/core/syntax/scope.rs)
 // released under the MIT license by @defuz
 use bitflags::bitflags;
-use serde::{Deserialize, Serialize};
+use serde_derive::{Deserialize, Serialize};
 
 /// Foreground and background colors, with font style
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]

src/highlighting/theme.rs

@@ -2,7 +2,7 @@
 // released under the MIT license by @defuz
 use super::style::*;
 use super::selector::*;
-use serde::{Deserialize, Serialize};
+use serde_derive::{Deserialize, Serialize};
 
 /// A theme parsed from a `.tmTheme` file.
 ///

src/highlighting/theme_set.rs

@@ -2,7 +2,7 @@ use super::super::LoadingError;
 #[cfg(feature = "plist-load")]
 use super::settings::*;
 use super::theme::Theme;
-use serde::{Deserialize, Serialize};
+use serde_derive::{Deserialize, Serialize};
 use std::collections::BTreeMap;
 use std::path::{Path, PathBuf};
 

src/parsing/metadata.rs

@@ -7,8 +7,9 @@ use std::fs::File;
 use std::io::BufReader;
 use std::str::FromStr;
 
-use serde::{Deserialize, Deserializer, Serialize, Serializer};
-use serde_json;
+use serde::de::{Deserialize, Deserializer};
+use serde::ser::{Serialize, Serializer};
+use serde_derive::{Deserialize, Serialize};
 
 use super::regex::Regex;
 use super::scope::{MatchPower, Scope};

src/parsing/regex.rs

@@ -1,5 +1,6 @@
 use once_cell::sync::OnceCell;
-use serde::{Deserialize, Deserializer, Serialize, Serializer};
+use serde::de::{Deserialize, Deserializer};
+use serde::ser::{Serialize, Serializer};
 use std::error::Error;
 
 /// An abstraction for regex patterns.

src/parsing/scope.rs

@@ -9,8 +9,9 @@ use std::cmp::{Ordering, min};
 use std::mem;
 
 use once_cell::sync::Lazy;
-use serde::{Deserialize, Deserializer, Serialize, Serializer};
-use serde::de::{Error, Visitor};
+use serde::de::{Deserialize, Deserializer, Error, Visitor};
+use serde::ser::{Serialize, Serializer};
+use serde_derive::{Deserialize, Serialize};
 
 /// Scope related errors
 #[derive(Debug, thiserror::Error)]

src/parsing/syntax_definition.rs

@@ -9,7 +9,8 @@ use std::hash::Hash;
 use super::{scope::*, ParsingError};
 use super::regex::{Regex, Region};
 use regex_syntax::escape;
-use serde::{Deserialize, Serialize, Serializer};
+use serde::ser::{Serialize, Serializer};
+use serde_derive::{Deserialize, Serialize};
 use crate::parsing::syntax_set::SyntaxSet;
 
 pub type CaptureMapping = Vec<(usize, Vec<Scope>)>;

src/parsing/syntax_set.rs

@@ -17,7 +17,7 @@ use std::mem;
 use super::regex::Regex;
 use crate::parsing::syntax_definition::ContextId;
 use once_cell::sync::OnceCell;
-use serde::{Deserialize, Serialize};
+use serde_derive::{Deserialize, Serialize};
 
 /// A syntax set holds multiple syntaxes that have been linked together.
 ///