Fixes error message

Author: Andy-Python-Programmer

src/cargo/util/config/mod.rs

@@ -452,7 +452,7 @@ impl Config {
         } else if let Some(dir) = env::var_os("CARGO_TARGET_DIR") {
             // Check if the CARGO_TARGET_DIR environment variable is set to an empty string.
             if dir.to_string_lossy() == "" {
-                anyhow::bail!("the target directory is set to an empty string in the CARGO_TARGET_DIR environment variable.")
+                anyhow::bail!("the target directory is set to an empty string in the `CARGO_TARGET_DIR` environment variable")
             }
 
             Ok(Some(Filesystem::new(self.cwd.join(dir))))
@@ -461,9 +461,10 @@ impl Config {
 
             // Check if the target directory is set to an empty string in the config.toml file.
             if val.raw_value() == "" {
-                anyhow::bail!(
-                    "the target directory is set to an empty string in the config.toml file.",
-                )
+                anyhow::bail!(format!(
+                    "the target directory is set to an empty string in {}",
+                    val.value().definition
+                ),)
             }
 
             Ok(Some(Filesystem::new(path)))

src/cargo/util/config/path.rs

@@ -10,6 +10,11 @@ use std::path::PathBuf;
 pub struct ConfigRelativePath(Value<String>);
 
 impl ConfigRelativePath {
+    /// Returns the underlying value.
+    pub fn value(&self) -> &Value<String> {
+        &self.0
+    }
+
     /// Returns the raw underlying configuration value for this key.
     pub fn raw_value(&self) -> &str {
         &self.0.val

tests/testsuite/config.rs

@@ -1497,7 +1497,7 @@ target-dir = ''
 
     assert_error(
         config.target_dir().unwrap_err(),
-        "the target directory is set to an empty string in the config.toml file.",
+        "the target directory is set to an empty string in [..]/.cargo/config",
     );
 }