[ruby-core:119630] [Ruby master Feature#20815] Fetch for nested hash

["byroot (Jean Boussier) via ruby-core" <ruby-core@ml.ruby-lang.org>]

Issue #20815 has been updated by byroot (Jean Boussier).

Status changed from Open to Closed

Closing because it's a duplicate.

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Feature #20815: Fetch for nested hash 
https://bugs.ruby-lang.org/issues/20815#change-110252

* Author: dmytrostrukov (Dmytro Strukov)
* Status: Closed
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I propose adding a `fetch_nested` method to Ruby’s Hash class, allowing developers to fetch values deeply nested within a hash, with an error raised if any key in the provided path is missing. The method would be similar to dig, but with the added functionality of error handling when keys are not found, improving code readability and robustness when accessing nested data structures.

**Rationale**

- Enhanced Error Handling: `fetch_nested` would raise an error if a key in the specified path does not exist, which is critical for cases where the absence of specific keys indicates a data integrity issue or invalid structure. This makes debugging easier and helps catch issues early in the development process.
- Improved Code Readability: Without `fetch_nested`, developers often chain multiple fetch calls or rely on error-prone conditional checks, complicating code. A single `fetch_nested` method call would simplify syntax and improve readability when working with deeply nested hashes.
- Alignment with Ruby’s Error-First Philosophy: Ruby’s fetch method already offers error handling for missing keys at the top level of a hash. Extending this philosophy to nested hashes would offer consistency and convenience, aligning with Ruby’s emphasis on developer-friendly and expressive error handling.

**Example Usage**

``` ruby
data = { user: { profile: { name: "Alice" } } }

# Current approach
data.fetch(:user).fetch(:profile).fetch(:name) # Or use dig without error handling

# Proposed `fetch_nested`
data.fetch_nested(:user, :profile, :name) # Raises KeyError if any key is missing

```





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