fix(cli): stop overwriting output files (#15)

Cargo.toml

@@ -19,6 +19,7 @@ exclude = ["/.github/*"]
 [dependencies]
 clap = { version = "4.3.19", features = ["derive"] }
 indexmap = "2.0.0"
+owo-colors = "3.5.0"
 
 [dev-dependencies]
 pretty_assertions = { version= "1.4.0" }

src/main.rs

@@ -5,6 +5,7 @@ use std::process;
 
 use bulloak::*;
 use clap::Parser;
+use owo_colors::OwoColorize;
 
 #[derive(Parser)]
 #[command(author, version, about, long_about = None)] // Read from `Cargo.toml`
@@ -24,9 +25,16 @@ struct Config {
     /// Whether to write to files instead of stdout.
     ///
     /// This will write the output for each input file to the file
-    /// specified at the root of the input file.
-    #[arg(short = 'w', long = "write-files")]
+    /// specified at the root of the input file if the output file
+    /// doesn't already exist. To overwrite, use `--force-write`
+    /// together with `--write-files`.
+    #[arg(short = 'w', long, group = "file-handling")]
     write_files: bool,
+
+    /// When `write_files` is specified, use `--force-write` to
+    /// overwrite the output files.
+    #[arg(short = 'f', long, requires = "file-handling", default_value = "false")]
+    force_write: bool,
 }
 
 fn main() -> Result<()> {
@@ -41,14 +49,32 @@ fn main() -> Result<()> {
 }
 
 fn run(config: &Config) -> Result<()> {
+    // For each input file, compile it and print it or write it
+    // to the filesystem.
     for file in config.files.iter() {
         let text = fs::read_to_string(file)?;
         match scaffold(&text, config.with_actions_as_comments, config.indent) {
             Ok(compiled) => {
                 if config.write_files {
-                    let mut path = file.clone();
-                    path.set_file_name(compiled.output_file);
-                    fs::write(path, compiled.emitted)?;
+                    let mut output_path = file.clone();
+
+                    // Get the path to the output file.
+                    output_path.set_file_name(compiled.output_file);
+
+                    // Don't overwrite files unless `--force-write` was passed.
+                    if output_path.try_exists().is_ok() && !config.force_write {
+                        eprintln!(
+                            "{}: Skipped emitting to {:?}.\n      The file {:?} already exists.",
+                            "WARN".yellow(),
+                            file.as_path().blue(),
+                            output_path.as_path().blue()
+                        );
+                        continue;
+                    }
+
+                    if let Err(e) = fs::write(output_path, compiled.emitted) {
+                        eprintln!("{}: {}", "ERROR".red(), e);
+                    };
                 } else {
                     println!("{}", compiled.emitted);
                 }