YahooFinanceEx

Elixir client for the Yahoo! Finance API. Handles Yahoo's cookie + CSRF crumb authentication transparently.

⚠️ Yahoo's API is unofficial and undocumented. Endpoints, auth requirements, and response shapes can change without notice. This library tracks the patterns that worked at the time of writing; expect occasional breakage.

Status

v0.1 ships the smallest useful surface: single-symbol quote fetch. Planned follow-ups (none yet implemented):

batched quote fetch (get_quotes/1)
FX rates (get_fx_rate/2)
dividend history (get_dividend_history/2)
symbol search (search/2)
in-memory caching with TTL

Installation

def deps do
  [
    {:yahoo_finance_ex, "~> 0.1"}
  ]
end

Until published to Hex, use a git or path dependency:

def deps do
  [
    {:yahoo_finance_ex, github: "fleveque/yahoo_finance_ex"}
  ]
end

Usage

{:ok, quote} = YahooFinanceEx.get_quote("AAPL")

quote.symbol           #=> "AAPL"
quote.price            #=> 187.42
quote.currency         #=> "USD"
quote.dividend_yield   #=> 0.51
quote.ma200            #=> 175.00

Errors return {:error, reason} with one of:

:not_found — Yahoo returned an empty result for the symbol
{:auth_failed, _} — auth refresh failed after retries
{:http_status, status} — non-200 HTTP status from Yahoo
{:transport, reason} — network / transport error from Req

Architecture

YahooFinanceEx           # public API
├── Session              # GenServer: holds (cookie, crumb), refreshes on demand (60 s TTL)
├── Quote                # struct returned by get_quote/1
└── HTTP                 # private: wraps Req so tests can inject stubs

Session is started under the package's own supervisor as soon as :yahoo_finance_ex is started — no manual setup needed.

Testing your own code

All HTTP calls go through Req, so you can stub Yahoo's responses with Req.Test:

test "fetches a quote" do
  Req.Test.stub(YahooFinanceEx.HTTPStub, fn conn ->
    Req.Test.json(conn, %{
      "quoteResponse" => %{"result" => [%{"symbol" => "AAPL", "regularMarketPrice" => 187.42, ...}]}
    })
  end)

  # ...
end

See test/yahoo_finance_ex_test.exs for full setup including the Session GenServer's allowances.

License

MIT. See LICENSE.

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