Deduplicate and sort word lists when building

Also improves error reporting during the build phase.

Fixes #52.

Cargo.toml

@@ -29,6 +29,9 @@ default-rng = ["rand/std", "rand/std_rng"]
 # Allows the default word lists to be used.
 default-words = []
 
+[build-dependencies]
+anyhow = "^1.0.75"
+
 [dependencies]
 clap = { version = "^3.1.0", features = ["cargo", "derive"], optional = true }
 itertools = { version = "^0.10.3", default-features = false }

build.rs

@@ -1,9 +1,12 @@
+use anyhow::{Context, Result};
+use std::collections::HashSet;
 use std::env;
 use std::fs;
 use std::path::Path;
 
-fn main() {
-    let out_dir = env::var_os("OUT_DIR").unwrap();
+fn main() -> Result<()> {
+    let words_dir = Path::new("words");
+    let out_dir = env::var_os("OUT_DIR").context("OUT_DIR not set")?;
     let dest_path = Path::new(&out_dir).join("words.rs");
 
     let mut lines: Vec<String> = vec![];
@@ -14,17 +17,28 @@ fn main() {
     for list_size in list_sizes {
         lines.push(format!("pub mod {list_size} {{"));
         for list_name in list_names {
-            let list_path = format!("words/{list_size}/{list_name}.txt");
-            println!("cargo:rerun-if-changed={list_path}");
-            let list_raw = fs::read_to_string(list_path).unwrap();
-            let list = list_raw.split_whitespace().collect::<Vec<_>>();
+            let list_path = words_dir.join(list_size).join(list_name).with_extension("txt");
+            println!("cargo:rerun-if-changed={}", list_path.to_string_lossy());
+            let list_raw = fs::read_to_string(&list_path)
+                .with_context(|| format!("Could not read word list from {list_path:?}"))?;
+            let list = {
+                // Ensure we have no duplicates.
+                let words = list_raw.split_whitespace().collect::<HashSet<_>>();
+                // Collect into a `Vec` and sort it.
+                let mut list = words.into_iter().collect::<Vec<_>>();
+                list.sort();
+                list
+            };
             lines.push(format!("  pub static {}: [&str; {}] = [", list_name.to_uppercase(), list.len()));
             lines.extend(list.iter().map(|word| format!("    \"{word}\",")));
             lines.push("  ];".to_string());
         }
         lines.push("}".to_string());
     }
 
-    fs::write(dest_path, lines.join("\n")).unwrap();
+    fs::write(&dest_path, lines.join("\n"))
+        .with_context(|| format!("Could not write word lists to output file {dest_path:?}"))?;
     println!("cargo:rerun-if-changed=build.rs");
+
+    Ok(())
 }