install: with -t, check if we aren't passed a file

Should pass tests/install/basic-1

src/uu/install/src/install.rs

@@ -66,6 +66,7 @@ enum InstallError {
     InvalidUser(String),
     InvalidGroup(String),
     OmittingDirectory(PathBuf),
+    NotADirectory(PathBuf),
 }
 
 impl UError for InstallError {
@@ -120,6 +121,9 @@ impl Display for InstallError {
             Self::InvalidUser(user) => write!(f, "invalid user: {}", user.quote()),
             Self::InvalidGroup(group) => write!(f, "invalid group: {}", group.quote()),
             Self::OmittingDirectory(dir) => write!(f, "omitting directory {}", dir.quote()),
+            Self::NotADirectory(dir) => {
+                write!(f, "failed to access {}: Not a directory", dir.quote())
+            }
         }
     }
 }
@@ -583,6 +587,13 @@ fn standard(mut paths: Vec<String>, b: &Behavior) -> UResult<()> {
                 }
             }
         }
+        if b.target_dir.is_some() {
+            let p = to_create.unwrap();
+
+            if !p.exists() || !p.is_dir() {
+                return Err(InstallError::NotADirectory(p.to_path_buf()).into());
+            }
+        }
     }
 
     if sources.len() > 1 || is_potential_directory_path(&target) {

tests/by-util/test_install.rs

@@ -1538,3 +1538,27 @@ fn test_install_compare_option() {
         .code_is(1)
         .stderr_contains("Options --compare and --strip are mutually exclusive");
 }
+
+#[test]
+// Matches part of tests/install/basic-1
+fn test_t_exist_dir() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+
+    let source1 = "file";
+    let target_dir = "sub4/";
+    let target_file = "sub4/file_exists";
+
+    at.touch(source1);
+    at.mkdir(target_dir);
+    at.touch(target_file);
+
+    scene
+        .ucmd()
+        .arg("-t")
+        .arg(target_file)
+        .arg("-Dv")
+        .arg(source1)
+        .fails()
+        .stderr_contains("failed to access 'sub4/file_exists': Not a directory");
+}