Add String routine to all SDK types

[tjayrush]

Here's a conversation with Chat. Makes sense to me.

Me:

I am building a GoLang SDK. There are about 45 data structures of various types. The main endpoints of the SDK return one (or more) of those 45 structures.

Is it idiomatic Go to provide a String routine for each of the 45 structs?

ChatGPT:

In Go, it's common and often considered good practice to implement the String() method for types, particularly when the type's default representation (such as the one provided by fmt.Println or fmt.Printf with the %v verb) doesn't provide clear or useful information about the instance. This method is part of the Stringer interface from the fmt package, which looks like this:

type Stringer interface {
    String() string
}

Implementing String() for your data structures can significantly improve the usability and debuggability of your SDK, as it allows users (and you, the developer) to print more human-readable representations of struct instances directly. This is especially useful for logging, debugging, and any other situation where understanding the content of a struct at a glance is beneficial.

However, whether you should implement this method for all 45 structs in your SDK depends on a few factors:

Relevance: Does every struct benefit from a custom string representation? If some structs are simple or used internally where a custom string format isn't useful, it might not be necessary.

Maintenance: More code means more to maintain. Ensure that the benefits of implementing these methods outweigh the maintenance overhead.

Performance: While unlikely to be a significant issue for most applications, consider the performance impact if the string representations are complex or called frequently.

Idiomatic Go: Go encourages simplicity and pragmatism. Implementing String() is idiomatic when it serves a clear purpose, such as improving readability or aiding in debugging. However, Go also values minimalism, so adding methods that don't provide tangible benefits might be seen as unnecessary.

In practice, for a public-facing SDK, providing String() methods for your data structures can greatly enhance the developer experience. It's idiomatic to do so for structs that are exposed to users of the SDK, particularly for complex structures or those where the default representation might be confusing or unhelpful. For each struct, consider if the String() method:

• Adds clarity to what the struct represents,
• Is likely to be used in logging or debugging scenarios,
• Helps in documenting the SDK by providing clear examples of the struct's contents.

For internal structures or those with straightforward, clear default representations, it might be acceptable to skip the custom String() implementation. Ultimately, the decision should balance the benefits of added clarity and usability against the cost of writing and maintaining additional code.

Me:

Thanks. My String functions will look like this:

func (s *TypeName) String() string {
   bytes, _ := json.UnmarshalIndented(s, "", "    ")
   return string(bytes)
}

Is this idomatic?

Should the final " " be a tab or spaces if I wanted it to be more idiomatic

What does the first "" do?

I'm going it seems ignoring the error is the only way to work. Your thoughts?

ChatGPT:

You've got a neat idea for implementing the String() method, using JSON to give a structured and readable representation of your structs. However, there are a few points to address in your snippet:

Method to Use: You likely meant to use json.MarshalIndent instead of json.UnmarshalIndented, as you're looking to convert your struct into an indented JSON string. json.Unmarshal is for decoding JSON data into a Go data structure, while json.MarshalIndent is for encoding a Go data structure into a formatted JSON string.

Indentation: As for whether to use tabs or spaces, Go doesn't enforce a strict rule in this context since it's about the output format of a string. However, Go code itself is conventionally formatted with tabs (as enforced by gofmt), but for JSON output, spaces are more common and can be considered idiomatic because JSON is often consumed in environments where tab width can vary. The choice between tabs and spaces for JSON output should consider how the JSON is most likely to be viewed.

The First "" Parameter: In the json.MarshalIndent function, the first "" is the prefix argument. It's a string to prepend to each line of output. In most cases, this is left as an empty string because you're formatting the content of the structure, not adding additional context or padding at the start of each line.

Ignoring Errors: In Go, it's generally not idiomatic to ignore errors. Ignoring errors can lead to difficult-to-debug issues, especially in cases where the operation might fail under certain conditions (e.g., marshaling a struct with unexported fields or circular references). It's better to handle the error, perhaps by logging it or defaulting to a simpler representation if marshaling fails.

Here's how you might rewrite your method, taking these points into account:

func (s *TypeName) String() string {
    bytes, err := json.MarshalIndent(s, "", "    ")
    if err != nil {
        // Handle the error in an appropriate way for your application
        // For example, return a simple error message or a basic string representation
        log.Printf("error marshaling TypeName to JSON: %v", err)
        return fmt.Sprintf("TypeName: error formatting")
    }
    return string(bytes)
}

In this revision:

• The correct function, json.MarshalIndent, is used.
• An error check is added, with a simple log statement as an example of error handling. Adjust this based on how you want to deal with errors in your application.
• The indentation uses four spaces, which is common for JSON data.
• Choosing between tabs and spaces for JSON is more about the consumer of your String() method's output than about Go idiomatic practices. If your primary audience is developers who will view this in code editors where tab width is adjustable, tabs might make sense. However, spaces are universally consistent in width and are a safe choice for JSON formatting.

Me:

I feel like this goes against minimalism. We presume the user will use a pretty printer with the results to check validity of the output. Buyer beware sort of thing.

Plus, in this specific case it seems very odd to return a string that is actually an error message.

ChatGPT:

You raise an important point about balancing the desire for minimalism and practicality in your Go code, especially regarding error handling and output formatting in the String() method. In the standard Go library, the approach to implementing String() varies widely based on the specific use case and what's most helpful for debugging or logging.

Minimalism and Practicality

Minimal Output: Many standard library types that implement String() opt for a minimal and straightforward representation. This often means not serializing the entire structure, especially if it's complex, but rather summarizing its state in a human-readable form. Error Handling: When it comes to error handling within a String() method, standard library types typically avoid complex logic. The method's purpose is to return a simple, informative string representation of the object. If generating this string could lead to errors (e.g., due to marshaling), it's common to see a simpler, fail-safe approach used instead.

Standard Library Practices

In the Go standard library, there's generally a reluctance to perform operations in String() methods that could fail or that are computationally expensive. The method is often used for logging or debugging, so the priority is on reliability and speed. For example:

Simplicity: Types like net.IP have a String() method that returns a straightforward textual representation of the IP address. There's no error handling involved because the operation is simple and guaranteed not to fail. Avoiding Errors in String(): There are few, if any, examples in the standard library where a String() method might return an error message as part of its output. The philosophy leans towards ensuring that String() is always able to return some meaningful output, even if it's not as detailed as it could be under perfect circumstances.

Recommendations Based on Standard Practices

Given the emphasis on reliability and simplicity, you might reconsider the approach of using JSON marshaling within String(), especially if it introduces complexity or potential for failure. If you do proceed with this approach:

Simplify When Possible: For a fail-safe, you might choose a very basic representation that avoids potential errors altogether. This could be as simple as returning the type's name or a very simplified view of its internal state that doesn't risk marshaling errors. Consider the Audience: Remember that String() is often used for logging or debugging. The output should be immediately helpful to developers without requiring additional tools or steps to interpret.

In summary, while using JSON marshaling inside String() is an interesting approach, aligning more closely with Go's standard library practices might mean opting for simplicity and reliability. Consider what information is most valuable for the contexts in which String() will be used and strive to provide that in the most straightforward manner possible.

Me:

The code in the SDK is auto-generated, so I prefer to generate identical code for every type (no special cases). Your thoughts?

ChatGPT:

Given that your SDK code is auto-generated and you prefer a uniform approach to implementing String() across all types to avoid special cases, the use of JSON marshaling becomes more understandable. In contexts where automation and consistency are key, especially with a large number of types, your strategy can indeed be both pragmatic and efficient. It ensures that every type has a readable, structured string representation with minimal manual intervention, which is particularly useful for logging, debugging, and perhaps even API responses.

Considerations for Auto-Generated Code

Uniformity: Uniform String() implementations across all types can greatly simplify the generation process and ensure consistency in how types are logged or debugged. This can be a significant advantage in auto-generated code, reducing the complexity of the code generation templates.

Error Handling: While traditionally, Go discourages ignoring errors, in this specific context—where the primary goal is to generate a debug-friendly representation of your types—the benefits of a consistent String() method might outweigh the risks of ignoring errors. To mitigate potential issues, you could log errors internally or adopt a fallback string representation in case of failure, although logging in a String() method might not always be appropriate due to the potential for generating excessive log output.

Performance Considerations: Be mindful of the performance implications of marshaling complex structures to JSON, especially if String() methods are called frequently in your application's critical paths. In most debugging or logging scenarios, this won't be a concern, but it's something to keep in mind.

Documentation and API Expectations: Clearly document that the String() methods on your types return JSON representations and discuss any potential implications this choice has for consumers of your SDK. This ensures users are aware of what to expect and how to best utilize the String() output.

Final Thoughts

Given the auto-generated nature of your SDK and the desire for uniformity, your approach is reasonable. It offers a good balance between the practical benefits of consistent, structured string representations and the idiomatic Go practice of simplicity. Just ensure you're mindful of the potential caveats related to error handling and performance, and clearly communicate with users of your SDK about the nature of the String() output.

This strategy highlights an interesting aspect of software development: while there are best practices and idiomatic ways of doing things, practical considerations and specific project contexts often necessitate tailored approaches. Your approach is a thoughtful compromise given the constraints and goals of your project.

[tjayrush]

We use a pointer in the Stringer method (even though we do not -- nor do we want to -- modify the input) because:

• Other routines on types generally take pointers
• Some of the structs are large and we don't want to have to make copies.