Use anyhow in build script

Cargo.lock

@@ -74,6 +74,12 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "anyhow"
+version = "1.0.75"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4668cab20f66d8d020e1fbc0ebe47217433c1b6c8f2040faf858554e394ace6"
+
 [[package]]
 name = "assert_cmd"
 version = "2.0.12"
@@ -106,6 +112,7 @@ name = "bat"
 version = "0.24.0"
 dependencies = [
  "ansi_colours",
+ "anyhow",
  "assert_cmd",
  "bincode",
  "bugreport",

Cargo.toml

@@ -98,6 +98,9 @@ tempfile = "3.8.1"
 [target.'cfg(unix)'.dev-dependencies]
 nix = { version = "0.26.4", default-features = false, features = ["term"] }
 
+[build-dependencies]
+anyhow = "1.0.75"
+
 [build-dependencies.clap]
 version = "4.4.6"
 optional = true

build.rs

@@ -4,9 +4,8 @@
 fn main() {}
 
 #[cfg(feature = "application")]
-fn main() -> Result<(), Box<dyn std::error::Error>> {
+fn main() -> anyhow::Result<()> {
     use std::collections::HashMap;
-    use std::error::Error;
     use std::fs;
     use std::path::Path;
 
@@ -21,7 +20,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         variables: &HashMap<&str, &str>,
         in_file: &str,
         out_file: impl AsRef<Path>,
-    ) -> Result<(), Box<dyn Error>> {
+    ) -> anyhow::Result<()> {
         let mut content = fs::read_to_string(in_file)?;
 
         for (variable_name, value) in variables {
@@ -40,9 +39,11 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     variables.insert("PROJECT_EXECUTABLE_UPPERCASE", &executable_name_uppercase);
     variables.insert("PROJECT_VERSION", PROJECT_VERSION);
 
-    let out_dir_env = std::env::var_os("BAT_ASSETS_GEN_DIR")
-        .or_else(|| std::env::var_os("OUT_DIR"))
-        .expect("BAT_ASSETS_GEN_DIR or OUT_DIR to be set in build.rs");
+    let Some(out_dir_env) =
+        std::env::var_os("BAT_ASSETS_GEN_DIR").or_else(|| std::env::var_os("OUT_DIR"))
+    else {
+        anyhow::bail!("BAT_ASSETS_GEN_DIR or OUT_DIR should be set for build.rs");
+    };
     let out_dir = Path::new(&out_dir_env);
 
     fs::create_dir_all(out_dir.join("assets/manual")).unwrap();