feat: partial support for v2 syntax [trishume#323]

This adds support for the `extends` keyword. The implementation is very
hacky right now:

- We now require an optional `base_syntax` when parsing a syntax, if the
  `base_syntax` is not present and we find an `extends` keyword at the
  top level, we error out reporting which syntax file we expected.
- SyntaxSet collects this error and resolves the syntaxes in a loop
  until no more syntaxes can be resolved.
- We don't handle multiple-inheritance (`extends` might be a list).
- We don't re-evaluate the `contexts` as defined in the spec (you can
  override variables and have that affect the context).
- We only handle `extends` for syntaxes added through
  `SyntaxSet::load_from_folder`.

src/parsing/syntax_definition.rs

@@ -51,7 +51,7 @@ pub struct Context {
     pub meta_scope: Vec<Scope>,
     pub meta_content_scope: Vec<Scope>,
     /// This being set false in the syntax file implies this field being set false,
-    /// but it can also be set falso for contexts that don't include the prototype for other reasons
+    /// but it can also be set false for contexts that don't include the prototype for other reasons
     pub meta_include_prototype: bool,
     pub clear_scopes: Option<ClearAmount>,
     /// This is filled in by the linker at link time
@@ -75,6 +75,27 @@ impl Context {
             prototype: None,
         }
     }
+
+    pub(crate) fn extend(&mut self, other: Context) {
+        let Context {
+            meta_scope,
+            meta_content_scope,
+            meta_include_prototype,
+            clear_scopes,
+            prototype,
+            uses_backrefs,
+            patterns,
+        } = other;
+        self.meta_scope.extend(meta_scope);
+        self.meta_content_scope.extend(meta_content_scope);
+        self.meta_include_prototype = meta_include_prototype;
+        self.clear_scopes = clear_scopes;
+        if self.prototype.is_none() || prototype.is_some() {
+            self.prototype = prototype;
+        }
+        self.uses_backrefs |= uses_backrefs;
+        self.patterns.extend(patterns);
+    }
 }
 
 #[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]

src/parsing/syntax_set.rs

@@ -13,6 +13,7 @@ use std::fs::File;
 use std::io::{self, BufRead, BufReader};
 use std::mem;
 use std::path::Path;
+use std::path::PathBuf;
 
 use super::regex::Regex;
 use crate::parsing::syntax_definition::ContextId;
@@ -83,6 +84,7 @@ pub(crate) struct LazyContexts {
 pub struct SyntaxSetBuilder {
     syntaxes: Vec<SyntaxDefinition>,
     path_syntaxes: Vec<(String, usize)>,
+    extends_syntaxes: Vec<(PathBuf, String)>,
     #[cfg(feature = "metadata")]
     raw_metadata: LoadMetadata,
 
@@ -108,6 +110,23 @@ fn load_syntax_file(
     .map_err(|e| LoadingError::ParseSyntax(e, format!("{}", p.display())))
 }
 
+#[cfg(feature = "yaml-load")]
+fn load_syntax_file_with_extends(
+    p: &Path,
+    base_syntax: &SyntaxDefinition,
+    lines_include_newline: bool,
+) -> Result<SyntaxDefinition, LoadingError> {
+    let s = std::fs::read_to_string(p)?;
+
+    SyntaxDefinition::load_from_str_extended(
+        &s,
+        Some(base_syntax),
+        lines_include_newline,
+        p.file_stem().and_then(|x| x.to_str()),
+    )
+    .map_err(|e| LoadingError::ParseSyntax(e, format!("{}", p.display())))
+}
+
 impl Clone for SyntaxSet {
     fn clone(&self) -> SyntaxSet {
         SyntaxSet {
@@ -375,6 +394,7 @@ impl SyntaxSet {
         SyntaxSetBuilder {
             syntaxes: builder_syntaxes,
             path_syntaxes,
+            extends_syntaxes: Vec::new(),
             #[cfg(feature = "metadata")]
             existing_metadata: Some(metadata),
             #[cfg(feature = "metadata")]
@@ -516,6 +536,8 @@ impl SyntaxSetBuilder {
         folder: P,
         lines_include_newline: bool,
     ) -> Result<(), LoadingError> {
+        use super::ParseSyntaxError;
+
         for entry in crate::utils::walk_dir(folder).sort_by(|a, b| a.file_name().cmp(b.file_name()))
         {
             let entry = entry.map_err(LoadingError::WalkDir)?;
@@ -524,7 +546,27 @@ impl SyntaxSetBuilder {
                 .extension()
                 .map_or(false, |e| e == "sublime-syntax")
             {
-                let syntax = load_syntax_file(entry.path(), lines_include_newline)?;
+                let syntax = match load_syntax_file(entry.path(), lines_include_newline) {
+                    Ok(syntax) => syntax,
+                    // We are extending another syntax, look it up in the set first
+                    Err(LoadingError::ParseSyntax(
+                        ParseSyntaxError::ExtendsNotFound { name, extends },
+                        _,
+                    )) => {
+                        if let Some(ix) = self
+                            .path_syntaxes
+                            .iter()
+                            .find(|(s, _)| s.ends_with(extends.as_str()))
+                            .map(|(_, ix)| *ix)
+                        {
+                            todo!("lookup {ix} and pass to {name}");
+                        }
+                        self.extends_syntaxes
+                            .push((entry.path().to_path_buf(), extends));
+                        continue;
+                    }
+                    Err(err) => return Err(err),
+                };
                 if let Some(path_str) = entry.path().to_str() {
                     // Split the path up and rejoin with slashes so that syntaxes loaded on Windows
                     // can still be loaded the same way.
@@ -550,6 +592,45 @@ impl SyntaxSetBuilder {
         Ok(())
     }
 
+    fn resolve_extends(&mut self) {
+        let mut prev_len = usize::MAX;
+        // Loop while syntaxes are being resolved
+        while !self.extends_syntaxes.is_empty() && prev_len > self.extends_syntaxes.len() {
+            prev_len = self.extends_syntaxes.len();
+            // Split borrows to make the borrow cheker happy
+            let syntaxes = &mut self.syntaxes;
+            let paths = &mut self.path_syntaxes;
+            // Resolve syntaxes
+            self.extends_syntaxes.retain(|(path, extends)| {
+                let Some(ix) = paths
+                    .iter()
+                    .find(|(s, _)| s.ends_with(extends.as_str()))
+                    .map(|(_, ix)| *ix)
+                else {
+                    return true;
+                };
+                let base_syntax = &syntaxes[ix];
+                // FIXME: don't unwrap
+                let syntax = load_syntax_file_with_extends(path, base_syntax, false).unwrap();
+                if let Some(path_str) = path.to_str() {
+                    // Split the path up and rejoin with slashes so that syntaxes loaded on Windows
+                    // can still be loaded the same way.
+                    let path = Path::new(path_str);
+                    let path_parts: Vec<_> = path.iter().map(|c| c.to_str().unwrap()).collect();
+                    paths.push((path_parts.join("/").to_string(), syntaxes.len()));
+                }
+                syntaxes.push(syntax);
+                false
+            });
+        }
+
+        if !self.extends_syntaxes.is_empty() {
+            dbg!(&self.path_syntaxes);
+            dbg!(&self.extends_syntaxes);
+            todo!("warn, unresolved syntaxes");
+        }
+    }
+
     /// Build a [`SyntaxSet`] from the syntaxes that have been added to this
     /// builder.
     ///
@@ -571,16 +652,20 @@ impl SyntaxSetBuilder {
     /// directly load the [`SyntaxSet`].
     ///
     /// [`SyntaxSet`]: struct.SyntaxSet.html
-    pub fn build(self) -> SyntaxSet {
+    pub fn build(mut self) -> SyntaxSet {
+        self.resolve_extends();
+
         #[cfg(not(feature = "metadata"))]
         let SyntaxSetBuilder {
             syntaxes: syntax_definitions,
             path_syntaxes,
+            extends_syntaxes: _,
         } = self;
         #[cfg(feature = "metadata")]
         let SyntaxSetBuilder {
             syntaxes: syntax_definitions,
             path_syntaxes,
+            extends_syntaxes: _,
             raw_metadata,
             existing_metadata,
         } = self;

src/parsing/yaml_load.rs

@@ -32,6 +32,9 @@ pub enum ParseSyntaxError {
     /// Syntaxes must have a context named "main"
     #[error("Context 'main' is missing")]
     MainMissing,
+    /// This syntax extends another syntax which is not available
+    #[error("Syntax for {name} extends {extends}, but {extends} could not be found")]
+    ExtendsNotFound { name: String, extends: String },
     /// Some part of the YAML file is the wrong type (e.g a string but should be a list)
     /// Sorry this doesn't give you any way to narrow down where this is.
     /// Maybe use Sublime Text to figure it out.
@@ -86,6 +89,15 @@ impl SyntaxDefinition {
         s: &str,
         lines_include_newline: bool,
         fallback_name: Option<&str>,
+    ) -> Result<SyntaxDefinition, ParseSyntaxError> {
+        SyntaxDefinition::load_from_str_extended(s, None, lines_include_newline, fallback_name)
+    }
+
+    pub(crate) fn load_from_str_extended(
+        s: &str,
+        extends: Option<&SyntaxDefinition>,
+        lines_include_newline: bool,
+        fallback_name: Option<&str>,
     ) -> Result<SyntaxDefinition, ParseSyntaxError> {
         let docs = match YamlLoader::load_from_str(s) {
             Ok(x) => x,
@@ -98,6 +110,7 @@ impl SyntaxDefinition {
         let mut scope_repo = SCOPE_REPO.lock().unwrap();
         SyntaxDefinition::parse_top_level(
             doc,
+            extends,
             scope_repo.deref_mut(),
             lines_include_newline,
             fallback_name,
@@ -106,20 +119,40 @@ impl SyntaxDefinition {
 
     fn parse_top_level(
         doc: &Yaml,
+        extends: Option<&SyntaxDefinition>,
         scope_repo: &mut ScopeRepository,
         lines_include_newline: bool,
         fallback_name: Option<&str>,
     ) -> Result<SyntaxDefinition, ParseSyntaxError> {
         let h = doc.as_hash().ok_or(ParseSyntaxError::TypeMismatch)?;
 
-        let mut variables = HashMap::new();
+        // Get variables from cloned syntax, will be overritten if the same is present as detailed
+        // in the spec
+        let mut variables = extends
+            .map(|syntax| syntax.variables.clone())
+            .unwrap_or_default();
         if let Ok(map) = get_key(h, "variables", |x| x.as_hash()) {
             for (key, value) in map.iter() {
                 if let (Some(key_str), Some(val_str)) = (key.as_str(), value.as_str()) {
                     variables.insert(key_str.to_owned(), val_str.to_owned());
                 }
             }
         }
+
+        let name = get_key(h, "name", |x| x.as_str())
+            .unwrap_or_else(|_| fallback_name.unwrap_or("Unnamed"))
+            .to_owned();
+        // FIXME: extends is allowed to be a list also
+        let extends = match (get_key(h, "extends", |x| x.as_str()), extends) {
+            (Ok(base_syntax), None) => {
+                return Err(ParseSyntaxError::ExtendsNotFound {
+                    name,
+                    extends: base_syntax.to_string(),
+                })
+            }
+            (Ok(_), Some(base_syntax)) => Some(base_syntax),
+            (Err(_), _) => None,
+        };
         let contexts_hash = get_key(h, "contexts", |x| x.as_hash())?;
         let top_level_scope = scope_repo
             .build(get_key(h, "scope", |x| x.as_str())?)
@@ -132,7 +165,11 @@ impl SyntaxDefinition {
             lines_include_newline,
         };
 
-        let mut contexts = SyntaxDefinition::parse_contexts(contexts_hash, &mut state)?;
+        let mut contexts = SyntaxDefinition::parse_contexts(
+            contexts_hash,
+            extends.map(|syntax| &syntax.contexts),
+            &mut state,
+        )?;
         if !contexts.contains_key("main") {
             return Err(ParseSyntaxError::MainMissing);
         }
@@ -147,9 +184,7 @@ impl SyntaxDefinition {
         }
 
         let defn = SyntaxDefinition {
-            name: get_key(h, "name", |x| x.as_str())
-                .unwrap_or_else(|_| fallback_name.unwrap_or("Unnamed"))
-                .to_owned(),
+            name,
             scope: top_level_scope,
             file_extensions,
             // TODO maybe cache a compiled version of this Regex
@@ -166,9 +201,11 @@ impl SyntaxDefinition {
 
     fn parse_contexts(
         map: &Hash,
+        extends: Option<&HashMap<String, Context>>,
         state: &mut ParserState<'_>,
     ) -> Result<HashMap<String, Context>, ParseSyntaxError> {
-        let mut contexts = HashMap::new();
+        // FIXME: contexts need to be re-evaluated with the new values of the variables
+        let mut contexts = extends.cloned().unwrap_or_default();
         for (key, value) in map.iter() {
             if let (Some(name), Some(val_vec)) = (key.as_str(), value.as_vec()) {
                 let is_prototype = name == "prototype";
@@ -194,13 +231,31 @@ impl SyntaxDefinition {
         is_prototype: bool,
         namer: &mut ContextNamer,
     ) -> Result<String, ParseSyntaxError> {
+        enum InsertMode {
+            Replace,
+            Prepend,
+            Append,
+        }
         let mut context = Context::new(!is_prototype);
         let name = namer.next();
+        let mut insert = InsertMode::Replace;
 
         for y in vec.iter() {
             let map = y.as_hash().ok_or(ParseSyntaxError::TypeMismatch)?;
 
             let mut is_special = false;
+            if let Ok(x) = get_key(map, "meta_prepend", |x| x.as_bool()) {
+                if x {
+                    insert = InsertMode::Prepend;
+                }
+                is_special = true;
+            }
+            if let Ok(x) = get_key(map, "meta_append", |x| x.as_bool()) {
+                if x {
+                    insert = InsertMode::Append;
+                }
+                is_special = true;
+            }
             if let Ok(x) = get_key(map, "meta_scope", |x| x.as_str()) {
                 context.meta_scope = str_to_scopes(x, state.scope_repo)?;
                 is_special = true;
@@ -237,7 +292,26 @@ impl SyntaxDefinition {
             }
         }
 
-        contexts.insert(name.clone(), context);
+        match insert {
+            InsertMode::Replace => {
+                contexts.insert(name.clone(), context);
+            }
+            InsertMode::Append => {
+                contexts
+                    .entry(name.clone())
+                    .and_modify(|ctx| ctx.extend(context.clone()))
+                    .or_insert(context);
+            }
+            InsertMode::Prepend => {
+                contexts
+                    .entry(name.clone())
+                    .and_modify(|ctx| {
+                        context.extend(ctx.clone());
+                        *ctx = context.clone();
+                    })
+                    .or_insert(context);
+            }
+        }
         Ok(name)
     }
 
@@ -887,7 +961,6 @@ impl<'a> Parser<'a> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::parsing::syntax_definition::*;
     use crate::parsing::Scope;
 
     #[test]