Merge pull request #18 from reaganmcf/node-mode-fallback

✨ cli::build_node_config() resolves exec_commands using package.json

Author: reaganmcf

Cargo.lock

@@ -25,3 +25,4 @@ walkdir = "2"
 log = "0.4.0"
 env_logger = "0.8.3"
 termcolor = "1.1.2"
+serde_json = "1.0"

Cargo.toml

@@ -1,6 +1,10 @@
+extern crate serde_json;
 use clap::{App, ArgMatches};
 use env_logger::Builder;
 use log::LevelFilter;
+use serde_json::Value;
+use std::fs::File;
+use std::io::BufReader;
 use std::path::Path;
 
 #[derive(Debug)]
@@ -67,12 +71,96 @@ impl Cli {
         config.unwrap()
     }
 
+    /// Build the `nodejs` configuration.
+    ///
+    /// ### Watch Patterns
+    /// [`.jsx`, `.js`, `.html`, `.css`]
+    ///
+    /// ### Exec Commands
+    /// If there is a `package.json` in the root directory, lightmon attempts to resolve the exec command
+    /// in the following order:
+    ///  1. The value at `scripts.start`
+    ///  2. The value at `scripts.run`
+    ///  3. `node main` where `main` is the value of the `main` key in `package.json` (the entry point of the project).
+    ///
+    /// **NOTE:** exec command will fallback to `node index.js` if all of the above fail.
+    ///
+    /// For example, the following `package.json` will result in the exec command resolving to
+    /// `react-scripts start`:
+    /// ```json
+    /// {
+    ///     "name": "calculator",
+    ///     "main": "index.js",
+    ///     "scripts": {
+    ///         "start": "react-scripts start"
+    ///         "build": "react-scripts build"
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// In this example, the exec command will resolve to `node my_entry_point.js`:
+    /// ```json
+    /// {
+    ///     "name": "bar",
+    ///     "main": "my_entry_point.js"
+    /// }
+    /// ```
     pub fn build_node_config() -> Self {
         debug!("Configuring for node mode...");
+        let watch_patterns: Vec<String> = vec![
+            ".jsx".to_string(),
+            ".js".to_string(),
+            ".html".to_string(),
+            ".css".to_string(),
+        ];
+        let mut exec_commands: Vec<String> = Vec::new();
+
+        if Path::new("package.json").exists() {
+            let file = File::open("package.json").unwrap();
+            let reader = BufReader::new(file);
+            let values: Value = serde_json::from_reader(reader).unwrap();
+
+            if values.is_object() {
+                if let Some(scripts) = values.get("scripts") {
+                    debug!("scripts found! Value is = {}", scripts);
+                    if let Some(scripts_start) = scripts.get("start") {
+                        debug!(
+                            "scripts.start found! Resolving exec_commands as '{}'",
+                            scripts_start
+                        );
+                        exec_commands.push(scripts_start.to_string());
+                    } else if let Some(scripts_run) = scripts.get("run") {
+                        debug!(
+                            "scripts.run found! Resolvig exec_commands as '{}'",
+                            scripts_run
+                        );
+                        exec_commands.push(scripts_run.to_string());
+                    }
+                }
+
+                // If scripts resolution failed, try getting main entry point
+                if exec_commands.is_empty() {
+                    if let Some(main_entry_point) = values.get("main") {
+                        debug!(
+                            "main found! Resolving exec_commands as '{}'",
+                            main_entry_point
+                        );
+                        exec_commands.push(format!("node {}", main_entry_point))
+                    }
+                }
+            }
+        }
+
+        // exec commands resolution fallback
+        if exec_commands.is_empty() {
+            debug!("Failed to resolve exec command using package.json, falling back to 'node index.js'");
+            exec_commands.push("node index.js".to_string());
+        }
+
         Cli {
-            watch_patterns: vec!["*.jsx".to_string(), ".js".to_string()],
+            watch_patterns,
             project_language: SupportedLanguage::Node,
-            exec_commands: vec!["npm start".to_string()],
+            exec_commands,
         }
     }