feat: add config_get and tests

[mhmd-azeez]

No description provided.

[bhelx]

sorry, didn't really finish this conversation: https://github.com/dylibso/mcp.run/pull/68#discussion_r1878277435

but the type system has no way of knowing if this is ever null

[bhelx]

fortunately i think js treats empty string as falsey here

[mhmd-azeez]

It seems like none of hte bindgens used in this repo can handle nullable output:

• TS:

/**
 * Get the configuration for the tool
 *
 * @param {string} input - The config key
 * @returns {string | null} The config value for the given key, or empty if not found
 */
export function config_get(input: string): string | null {
  const mem = Memory.fromString(input as string);

  const ptr = hostFunctions.config_get(mem.offset);

  return Memory.find(ptr).readJsonObject();
}

Panic at call: Uncaught TypeError: cannot read property 'readJsonObject' of undefined
    at config_get (script.js:128)
    at callImpl (script.js:137)
    at call (script.js:168)

• Rust:

/// config_get Get the configuration for the tool
/// It takes input of String (The config key)
/// And it returns an output Option<String> (The config value for the given key, or empty if not found)
#[allow(unused)]
pub(crate) fn config_get(input: String) -> std::result::Result<Option<String>, extism_pdk::Error> {
    let res = unsafe { raw_imports::config_get(input)? };

    let extism_pdk::Json(res) = res;

    Ok(res)
}

Panic at call: EOF while parsing a value at line 1 column 0.

• C++:

EXTISM_IMPORT_USER("config_get")
extern extism::imports::RawHandle config_get(extism::imports::RawHandle);

} // namespace imports

std::expected<std::string, Error> config_get(std::string_view input) {
  auto &encoded = input;
  auto in_handle = extism::UniqueHandle<char>::from(encoded);
  if (!in_handle) {
    return std::unexpected(Error::extism);
  }
  auto out_raw = imports::config_get(*in_handle);
  if (!out_raw) {
    return std::unexpected(Error::host_null); // <-- fails here
  }
  extism::UniqueHandle<char> out_handle(out_raw);
  auto out_string = out_handle.string();
  if (!out_string.size()) {
    return std::unexpected(Error::not_json);
  }
  return jsoncons::decode_json<std::string>(std::move(out_string));
}

[mhmd-azeez]

Since nullable json output is not very well supported currently, should we go back to contentType: text/plain for the output too?

[mhmd-azeez]

Also, should we rename config because of this?

[bhelx]

we might want to consider just doing--allow-host "*" for these.

[bhelx]

how will this work for file paths?

[mhmd-azeez]

xtp test doesnt have configuration for allowedPaths, so we cant test them yet

[nilslice]

we can use the Extism CLI too in a pinch

[mhmd-azeez]

closing in favor of #9

[nilslice]

did @bhelx get rid of this from the schema?

[mhmd-azeez]

yes, the prod schema no longer has the config_get import