Make sure that the merged documents don't have duplicate contents

cmd/soroban-cli/src/commands/contract/init.rs

@@ -433,19 +433,41 @@ fn check_internet_connection() -> bool {
     false
 }
 
+// Appends the contents of a file to another file, separated by a delimiter
 fn append_contents(from: &Path, to: &Path) -> Result<(), Error> {
     let mut from_file = File::open(from)?;
     let mut from_content = String::new();
     from_file.read_to_string(&mut from_content)?;
 
-    let mut to_file = OpenOptions::new().append(true).open(to)?;
-    to_file.write_all("\n\n".as_bytes())?;
+    let mut to_file = OpenOptions::new().read(true).append(true).open(to)?;
+    let mut to_content = String::new();
+    to_file.read_to_string(&mut to_content)?;
+
+    let delimiter = get_merged_file_delimiter(to)?;
+    // if the to file already contains the delimiter, we don't need to append the contents again
+    if to_content.contains(&delimiter) {
+        return Ok(());
+    }
+
+    to_file.write_all(delimiter.as_bytes())?;
     to_file.write_all(from_content.as_bytes())?;
 
     println!("ℹ️  Merging {} contents", &to.to_string_lossy());
     Ok(())
 }
 
+fn get_merged_file_delimiter(file_path: &Path) -> Result<String, Error> {
+    let comment = if file_path.to_string_lossy().contains("README.md") {
+        "[//]: # \"The following is the Frontend Template's README.md\"".to_string()
+    } else if file_path.to_string_lossy().contains("gitignore") {
+        "# The following is from the Frontend Template's .gitignore".to_string()
+    } else {
+        "".to_string()
+    };
+
+    Ok(format!("\n\n---\n\n{comment}\n\n").to_string())
+}
+
 #[cfg(test)]
 mod tests {
     use std::fs::read_to_string;
@@ -553,7 +575,43 @@ mod tests {
         assert_astro_files_exist(&project_dir);
         assert_gitignore_includes_astro_paths(&project_dir);
         assert_package_json_files_have_correct_name(&project_dir);
-        assert_readme_includes_frontend_file_appended(&project_dir);
+        assert_readme_includes_frontend_readme_appended(&project_dir);
+
+        temp_dir.close().unwrap();
+    }
+
+    #[test]
+    fn test_init_does_not_duplicate_frontend_readme_contents_when_run_more_than_once() {
+        let temp_dir = tempfile::tempdir().unwrap();
+        let project_dir = temp_dir.path().join(TEST_PROJECT_NAME);
+        let with_examples = vec![];
+        init(
+            project_dir.as_path(),
+            &"https://github.com/AhaLabs/soroban-astro-template".to_string(),
+            &with_examples,
+        )
+        .unwrap();
+
+        // call init again to make sure the README.md's contents are not duplicated
+        init(
+            project_dir.as_path(),
+            &"https://github.com/AhaLabs/soroban-astro-template".to_string(),
+            &with_examples,
+        )
+        .unwrap();
+
+        assert_base_template_files_exist(&project_dir);
+        assert_default_hello_world_contract_files_exist(&project_dir);
+        assert_base_excluded_paths_do_not_exist(&project_dir);
+
+        // check that the contract's Cargo.toml file uses the workspace for dependencies
+        assert_contract_cargo_file_uses_workspace(&project_dir, "hello_world");
+        assert_base_excluded_paths_do_not_exist(&project_dir);
+
+        assert_astro_files_exist(&project_dir);
+        assert_gitignore_includes_astro_paths(&project_dir);
+        assert_package_json_files_have_correct_name(&project_dir);
+        assert_readme_includes_frontend_readme_appended(&project_dir);
 
         temp_dir.close().unwrap();
     }
@@ -629,9 +687,20 @@ mod tests {
         assert!(package_lock_json_str.contains(&format!("\"name\":\"{TEST_PROJECT_NAME}\"")));
     }
 
-    fn assert_readme_includes_frontend_file_appended(project_dir: &Path) {
+    fn assert_readme_includes_frontend_readme_appended(project_dir: &Path) {
         let readme_path = project_dir.join("README.md");
         let readme_str = read_to_string(readme_path).unwrap();
         assert!(readme_str.contains("Soroban Frontend in Astro"));
+        let expected = "[//]: # \"The following is the Frontend Template's README.md\"";
+        assert!(readme_str.contains(expected));
+
+        let readme_path = project_dir.join("README.md");
+        let readme_str = read_to_string(readme_path).unwrap();
+        println!("readme_str: {}", readme_str);
+        let readme_frontend_merge_delimiter =
+            "[//]: # \"The following is the Frontend Template's README.md\"";
+        let count = readme_str.matches(readme_frontend_merge_delimiter).count();
+        // making sure it is in there just once so that it isn't duplicated if `contract init` is run again
+        assert!(count == 1);
     }
 }