cli: Missing config file shouldn't be an error

Just fall back on the default values for each configuration option.

cli/config/src/lib.rs

@@ -15,34 +15,31 @@ use std::{env, fs};
 /// components will use the [`get`][] method to parse that JSON to extract configuration fields
 /// that are specific to that component.
 pub struct Config {
-    location: PathBuf,
-    config: Value,
+    pub location: PathBuf,
+    pub config: Value,
 }
 
 impl Config {
-    fn find_config_file() -> Result<PathBuf> {
+    fn find_config_file() -> Result<Option<PathBuf>> {
         if let Ok(path) = env::var("TREE_SITTER_DIR") {
             let mut path = PathBuf::from(path);
             path.push("config.json");
-            return Ok(path);
+            return Ok(Some(path));
         }
 
         let xdg_path = Self::xdg_config_file()?;
         if xdg_path.is_file() {
-            return Ok(xdg_path);
+            return Ok(Some(xdg_path));
         }
 
         let legacy_path = dirs::home_dir()
             .ok_or(anyhow!("Cannot determine home directory"))?
             .join(".tree-sitter/config.json");
         if legacy_path.is_file() {
-            return Ok(legacy_path);
+            return Ok(Some(legacy_path));
         }
 
-        Err(anyhow!(concat!(
-            "Cannot find a tree-sitter configuration file.\n",
-            "Please run `tree-sitter init-config` to create one!"
-        )))
+        Ok(None)
     }
 
     fn xdg_config_file() -> Result<PathBuf> {
@@ -61,7 +58,10 @@ impl Config {
     ///   - `$HOME/.tree-sitter/config.json` as a fallback from where tree-sitter _used_ to store
     ///     its configuration
     pub fn load() -> Result<Config> {
-        let location = Self::find_config_file()?;
+        let location = match Self::find_config_file()? {
+            Some(location) => location,
+            None => return Config::initial(),
+        };
         let content = fs::read_to_string(&location)?;
         let config = serde_json::from_str(&content)?;
         Ok(Config { location, config })

cli/loader/src/lib.rs

@@ -104,6 +104,13 @@ impl Loader {
     }
 
     pub fn find_all_languages(&mut self, config: &Config) -> Result<()> {
+        if config.parser_directories.is_empty() {
+            eprintln!("Warning: You have not configured any parser directories!");
+            eprintln!("Please run `tree-sitter init-config` and edit the resulting");
+            eprintln!("configuration file to indicate where we should look for");
+            eprintln!("language grammars.");
+            eprintln!("");
+        }
         for parser_container_dir in &config.parser_directories {
             if let Ok(entries) = fs::read_dir(parser_container_dir) {
                 for entry in entries {

cli/src/main.rs

@@ -183,6 +183,10 @@ fn run() -> Result<()> {
         config.add(tree_sitter_loader::Config::initial())?;
         config.add(tree_sitter_cli::highlight::ThemeConfig::default())?;
         config.save()?;
+        println!(
+            "Saved initial configuration to {}",
+            config.location.display()
+        );
     } else if let Some(matches) = matches.subcommand_matches("generate") {
         let grammar_path = matches.value_of("grammar-path");
         let report_symbol_name = matches.value_of("report-states-for-rule").or_else(|| {