Add documentation

src/main.rs

@@ -20,7 +20,9 @@ struct Cli {
 
 #[derive(Subcommand, Debug)]
 enum Command {
+    #[clap(about = "Format a single file or stdin")]
     Fmt(FmtArgs),
+    #[clap(about = "Watch a file or directory for changes")]
     Watch(WatchArgs),
 }
 
@@ -28,31 +30,36 @@ enum Command {
 struct WatchArgs {
     path: PathBuf,
 
-    #[clap(short = 'e', long = "extension", default_values = ["jsonc", "jsoncc"])]
+    #[clap(short = 'e', long = "extension", default_values = ["jsonc", "jsoncc"], help = "File extensions to track")]
     extensions: Vec<OsString>,
 
-    #[clap(short = 'r', long = "recursive")]
+    #[clap(short = 'r', long = "recursive", help = "Recursively search files")]
     recursive: bool,
 
-    #[clap(short = 'I', long = "inplace")]
+    #[clap(short = 'I', long = "inplace", help = "Replace each file inplace")]
     inplace: bool,
 }
 
 #[derive(Args, Debug)]
 struct FmtArgs {
     // #[clap(short = 'i', long = "input")]
-    input: PathBuf,
+    #[clap(help = "Input file, or `-` for stdin")]
+    input: Option<PathBuf>,
 
-    #[clap(short = 'o', long = "output")]
+    #[clap(
+        short = 'o',
+        long = "output",
+        help = "Output file; will be stdout if no output is specified"
+    )]
     output: Option<PathBuf>,
 
-    #[clap(short = 'O', long = "json-output")]
+    #[clap(short = 'O', long = "json-output", help = "Output file for json")]
     json_output: Option<PathBuf>,
 
-    #[clap(short = 'c', long = "compact")]
+    #[clap(short = 'c', long = "compact", help = "Compact json format")]
     compact: bool,
 
-    #[clap(short = 'I', long = "inplace")]
+    #[clap(short = 'I', long = "inplace", help = "Replace file contents inplace")]
     inplace: bool,
 }
 
@@ -60,7 +67,9 @@ impl FmtArgs {
     /// Where should we format Jsonc output to?
     fn jsonc_output(&self) -> Option<JsoncOutput> {
         if self.inplace {
-            Some(JsoncOutput::File(&self.input))
+            Some(JsoncOutput::File(self.input.as_ref().expect(
+                "Argument parsing error -- input was empty, but --inplace was specified",
+            )))
         } else if let Some(ref output_file) = &self.output {
             Some(JsoncOutput::File(output_file))
         } else if self.json_output.is_some() {
@@ -81,8 +90,6 @@ enum JsoncOutput<'a> {
 fn main() -> Result<()> {
     let options = Cli::parse();
 
-    eprintln!("Options: {options:?}");
-
     match options.command {
         Command::Fmt(a) => {
             // TODO: Figure out how to validate this in clap Parser
@@ -93,7 +100,7 @@ fn main() -> Result<()> {
                 bail!("Cannot format --inplace when --output is specified");
             }
             format_single_file(
-                &a.input,
+                a.input.as_ref(),
                 a.jsonc_output().as_ref(),
                 a.json_output.as_ref(),
                 a.compact,
@@ -106,21 +113,25 @@ fn main() -> Result<()> {
 }
 
 fn format_single_file(
-    input: impl AsRef<Path>,
+    input: Option<impl AsRef<Path>>,
     jsonc_output: Option<&JsoncOutput>,
     json_output: Option<impl AsRef<Path>>,
     json_compact: bool,
 ) -> Result<()> {
-    let input_str = fs::read_to_string(&input).context("Reading input")?;
+    let input_str = if let Some(input_filename) = input {
+        fs::read_to_string(&input_filename).context("Reading input")?
+    } else {
+        std::io::read_to_string(std::io::stdin()).context("Reading stdin")?
+    };
 
     // First, format jsonc
     if let Some(jsonc_output) = jsonc_output {
-        let output = fjson::to_jsonc(&input_str).context("Formatting to jsonc")?;
+        let output = fjson::to_jsonc(&input_str).context("Parsing jsonc")?;
 
         match jsonc_output {
             JsoncOutput::Stdout => print!("{output}"),
             JsoncOutput::File(output_file) => AtomicFile::new(output_file, AllowOverwrite)
-                .write(|f| f.write_all(&output.as_bytes()))
+                .write(|f| f.write_all(output.as_bytes()))
                 .context("Writing jsonc output")?,
         }
     }
@@ -133,9 +144,13 @@ fn format_single_file(
             fjson::to_json_compact(&input_str).context("Formatting to json")
         }?;
 
-        AtomicFile::new(json_output_file, AllowOverwrite)
-            .write(|f| f.write_all(&output.as_bytes()))
-            .context("Writing jsonc output")?;
+        if json_output_file.as_ref().as_os_str() == "-" {
+            print!("{output}");
+        } else {
+            AtomicFile::new(json_output_file, AllowOverwrite)
+                .write(|f| f.write_all(output.as_bytes()))
+                .context("Writing jsonc output")?;
+        }
     }
 
     Ok(())
@@ -181,7 +196,7 @@ fn watch(args: &WatchArgs) -> Result<()> {
                 if !(args
                     .extensions
                     .iter()
-                    .any(|ext| (&path).extension() == Some(ext))
+                    .any(|ext| path.extension() == Some(ext))
                     || args.extensions.is_empty())
                 {
                     // This extension doesn't match their requested extensions
@@ -196,7 +211,7 @@ fn watch(args: &WatchArgs) -> Result<()> {
                 eprintln!("Got result: {path:#?}");
 
                 match format_single_file(
-                    &path,
+                    Some(&path),
                     Some(&JsoncOutput::File(&path)),
                     None::<&Path>,
                     false,