fix(cli): deduplicate formats, pre-validate before writing

crates/bin/src/cli.rs

@@ -1,7 +1,6 @@
 use std::{fs, path::PathBuf};
 
 use clap::Parser;
-use exporters;
 use lib::{BlockPalette, OutlineMode, TextBuilder, TtfFont};
 
 #[derive(Parser, Debug)]
@@ -144,18 +143,32 @@ pub fn run() -> anyhow::Result<()> {
         grid.depth
     );
 
-    let format_names: Vec<&str> = if cli.format.is_empty() {
+    let all_names = exporters::available_names();
+
+    let raw_formats: Vec<&str> = if cli.format.is_empty() {
         vec!["mcfunction"]
     } else if cli.format.iter().any(|f| f == "all") {
-        exporters::available_names()
+        all_names.clone()
     } else {
         cli.format.iter().map(String::as_str).collect()
     };
 
-    for name in format_names {
-        let exporter = exporters::build(name, &palette)
-            .ok_or_else(|| anyhow::anyhow!("unknown format '{}'. Available: {}", name, exporters::available_names().join(", ")))?;
+    // Deduplicate while preserving order
+    let mut seen = std::collections::HashSet::new();
+    let format_names: Vec<&str> = raw_formats
+        .into_iter()
+        .filter(|&name| seen.insert(name))
+        .collect();
 
+    // Pre-validate all names before writing anything
+    for name in &format_names {
+        if exporters::build(name, &palette).is_none() {
+            anyhow::bail!("unknown format '{}'. Available: {}", name, all_names.join(", "));
+        }
+    }
+
+    for name in format_names {
+        let exporter = exporters::build(name, &palette).unwrap(); // safe: pre-validated
         let output_bytes = exporter.export(&grid)?;
         let mut out_path = cli.out.clone();
         out_path.set_extension(exporter.file_extension());