Robust File Processor with Error Handling

This challenge focuses on implementing robust error handling in Go when processing files. You'll create a function that reads data from a file, performs a simple operation, and gracefully handles various potential errors that can occur during file operations and data processing. Mastering error handling is crucial for building reliable and user-friendly Go applications.

Problem Description

Your task is to implement a function called ProcessFile that takes a file path as a string and returns a processed string or an error.

The function should perform the following steps:

1. Open the file: Attempt to open the file specified by the given path.
2. Read the file content: Read all the content from the opened file.
3. Process the content: Convert the entire file content to uppercase.
4. Close the file: Ensure the file is properly closed after reading, regardless of whether an error occurred during reading.
5. Return the processed content or an error: If any step fails, return an appropriate error. If all steps succeed, return the uppercase content.

Key Requirements:

• The function signature must be func ProcessFile(filePath string) (string, error).
• Specific errors should be returned to indicate the cause of failure (e.g., file not found, read error, invalid data).
• Resource management is critical: the file must be closed using defer.

Expected Behavior:

• If the file exists and can be read without issues, and the content can be processed, the function should return the uppercase content and nil for the error.
• If the file does not exist or cannot be opened, an error indicating this should be returned.
• If there's an error during reading the file content, an error indicating a read error should be returned.
• The file should always be closed.

Edge Cases to Consider:

• An empty file.
• A file with special characters or non-UTF-8 encoded content (though for this problem, we assume UTF-8 and focus on file I/O errors).

Examples

Example 1:

Input: filePath = "test_files/sample.txt" (assuming test_files/sample.txt contains "hello world")

Output: "HELLO WORLD", nil

Explanation: The file is opened, its content "hello world" is read, converted to uppercase, and the file is closed. No errors occur.

Example 2:

Input: filePath = "non_existent_file.txt"

Output: "", <os.PathError> (The specific error will indicate "no such file or directory")

Explanation: The function attempts to open non_existent_file.txt, which doesn't exist. An os.PathError is returned, and the file is not opened, so there's nothing to close.

Example 3:

Input: filePath = "test_files/restricted_access.txt" (assuming a file that exists but the program doesn't have read permissions for)

Output: "", <os.PathError> (The specific error will indicate "permission denied")

Explanation: The function attempts to open restricted_access.txt, but lacks permissions. An os.PathError is returned. The defer statement will still attempt to close the file if it was partially opened, which is the correct behavior for defer.

Constraints

• The file path will be a valid string.
• The file content will be a UTF-8 encoded string.
• The maximum file size will not exceed 1MB.
• Your solution should be efficient for typical file sizes.

Notes

• Familiarize yourself with Go's os package for file operations and the errors package for error creation.
• Pay close attention to how defer works with resource cleanup, especially in the presence of errors.
• Consider using io.ReadAll for simplicity in reading the entire file content.
• When returning errors, aim to provide as much context as possible about what went wrong. You can wrap existing errors using fmt.Errorf with the %w verb to preserve the original error.