migrate grammar fetching/building code into helix-loader crate

This is a rather large refactor that moves most of the code for
loading, fetching, and building grammars into a new helix-loader
module. This works well with the [[grammars]] syntax for
languages.toml defined earlier: we only have to depend on the types
for GrammarConfiguration in helix-loader and can leave all the
[[language]] entries for helix-core.

1 files changed, 161 insertions, 0 deletions

diff --git a/helix-loader/src/lib.rs b/helix-loader/src/lib.rs
new file mode 100644
index 00000000..a2c4d96f
--- /dev/null
+++ b/helix-loader/src/lib.rs
@@ -0,0 +1,161 @@
+pub mod grammar;
+
+use etcetera::base_strategy::{choose_base_strategy, BaseStrategy};
+
+pub static RUNTIME_DIR: once_cell::sync::Lazy<std::path::PathBuf> =
+    once_cell::sync::Lazy::new(runtime_dir);
+
+pub fn runtime_dir() -> std::path::PathBuf {
+    if let Ok(dir) = std::env::var("HELIX_RUNTIME") {
+        return dir.into();
+    }
+
+    const RT_DIR: &str = "runtime";
+    let conf_dir = config_dir().join(RT_DIR);
+    if conf_dir.exists() {
+        return conf_dir;
+    }
+
+    if let Ok(dir) = std::env::var("CARGO_MANIFEST_DIR") {
+        // this is the directory of the crate being run by cargo, we need the workspace path so we take the parent
+        return std::path::PathBuf::from(dir).parent().unwrap().join(RT_DIR);
+    }
+
+    // fallback to location of the executable being run
+    std::env::current_exe()
+        .ok()
+        .and_then(|path| path.parent().map(|path| path.to_path_buf().join(RT_DIR)))
+        .unwrap()
+}
+
+pub fn config_dir() -> std::path::PathBuf {
+    // TODO: allow env var override
+    let strategy = choose_base_strategy().expect("Unable to find the config directory!");
+    let mut path = strategy.config_dir();
+    path.push("helix");
+    path
+}
+
+pub fn cache_dir() -> std::path::PathBuf {
+    // TODO: allow env var override
+    let strategy = choose_base_strategy().expect("Unable to find the config directory!");
+    let mut path = strategy.cache_dir();
+    path.push("helix");
+    path
+}
+
+pub fn config_file() -> std::path::PathBuf {
+    config_dir().join("config.toml")
+}
+
+pub fn lang_config_file() -> std::path::PathBuf {
+    config_dir().join("languages.toml")
+}
+
+pub fn log_file() -> std::path::PathBuf {
+    cache_dir().join("helix.log")
+}
+
+/// Default bultin-in languages.toml.
+pub fn default_lang_config() -> toml::Value {
+    toml::from_slice(include_bytes!("../../languages.toml"))
+        .expect("Could not parse bultin-in languages.toml to valid toml")
+}
+
+/// User configured languages.toml file, merged with the default config.
+pub fn user_lang_config() -> Result<toml::Value, toml::de::Error> {
+    let def_lang_conf = default_lang_config();
+    let data = std::fs::read(crate::config_dir().join("languages.toml"));
+    let user_lang_conf = match data {
+        Ok(raw) => {
+            let value = toml::from_slice(&raw)?;
+            merge_toml_values(def_lang_conf, value)
+        }
+        Err(_) => def_lang_conf,
+    };
+
+    Ok(user_lang_conf)
+}
+
+// right overrides left
+pub fn merge_toml_values(left: toml::Value, right: toml::Value) -> toml::Value {
+    use toml::Value;
+
+    fn get_name(v: &Value) -> Option<&str> {
+        v.get("name").and_then(Value::as_str)
+    }
+
+    match (left, right) {
+        (Value::Array(mut left_items), Value::Array(right_items)) => {
+            left_items.reserve(right_items.len());
+            for rvalue in right_items {
+                let lvalue = get_name(&rvalue)
+                    .and_then(|rname| left_items.iter().position(|v| get_name(v) == Some(rname)))
+                    .map(|lpos| left_items.remove(lpos));
+                let mvalue = match lvalue {
+                    Some(lvalue) => merge_toml_values(lvalue, rvalue),
+                    None => rvalue,
+                };
+                left_items.push(mvalue);
+            }
+            Value::Array(left_items)
+        }
+        (Value::Table(mut left_map), Value::Table(right_map)) => {
+            for (rname, rvalue) in right_map {
+                match left_map.remove(&rname) {
+                    Some(lvalue) => {
+                        let merged_value = merge_toml_values(lvalue, rvalue);
+                        left_map.insert(rname, merged_value);
+                    }
+                    None => {
+                        left_map.insert(rname, rvalue);
+                    }
+                }
+            }
+            Value::Table(left_map)
+        }
+        // Catch everything else we didn't handle, and use the right value
+        (_, value) => value,
+    }
+}
+
+#[cfg(test)]
+mod merge_toml_tests {
+    use super::merge_toml_values;
+
+    #[test]
+    fn language_tomls() {
+        use toml::Value;
+
+        const USER: &str = "
+        [[language]]
+        name = \"nix\"
+        test = \"bbb\"
+        indent = { tab-width = 4, unit = \"    \", test = \"aaa\" }
+        ";
+
+        let base: Value = toml::from_slice(include_bytes!("../../languages.toml"))
+            .expect("Couldn't parse built-in languages config");
+        let user: Value = toml::from_str(USER).unwrap();
+
+        let merged = merge_toml_values(base, user);
+        let languages = merged.get("language").unwrap().as_array().unwrap();
+        let nix = languages
+            .iter()
+            .find(|v| v.get("name").unwrap().as_str().unwrap() == "nix")
+            .unwrap();
+        let nix_indent = nix.get("indent").unwrap();
+
+        // We changed tab-width and unit in indent so check them if they are the new values
+        assert_eq!(
+            nix_indent.get("tab-width").unwrap().as_integer().unwrap(),
+            4
+        );
+        assert_eq!(nix_indent.get("unit").unwrap().as_str().unwrap(), "    ");
+        // We added a new keys, so check them
+        assert_eq!(nix.get("test").unwrap().as_str().unwrap(), "bbb");
+        assert_eq!(nix_indent.get("test").unwrap().as_str().unwrap(), "aaa");
+        // We didn't change comment-token so it should be same
+        assert_eq!(nix.get("comment-token").unwrap().as_str().unwrap(), "#");
+    }
+}