exoscale.interceptor — exoscale/interceptor 0.1.17

after-stage clj/s

(after-stage f after-f)

Modifies context after stage function ran

before-stage clj/s

(before-stage f before-f)

Wraps stage fn with another one, basically a middleware that will be run before a stage

discard clj/s

(discard f)

Run function for side-effects only and return context

enqueue clj/s

(enqueue ctx interceptors)

Adds interceptors to current context

error clj/s

(error ctx error)

Adds error to context, potentially triggering :error stage on current/next interceptor

execute clj/s

(execute ctx)

(execute ctx interceptors)

Executes a queue of Interceptors attached to the context. Context must be a map. Interceptors are added with exoscale.interceptor/enqueue.

An Interceptor is a map or map-like object with the keys :enter, :leave, and :error. The value of each key is a function; missing keys or nil values are ignored. When executing a context, first all the :enter functions are invoked in order. As this happens, the Interceptors are pushed onto a stack.

When execution reaches the end of the queue, it begins popping Interceptors off the stack and calling their :leave functions. Therefore :leave functions are called in the opposite order from :enter functions.

Both the :enter and :leave functions are called on a single argument, the context map, and return an updated context.

If any Interceptor function throws an exception, execution stops and begins popping Interceptors off the stack and calling their :error functions. The :error function takes two arguments: the context and the error triggering the call. If you rethrow the error or assoc it into the context under :exoscale.interceptor/error (or via the exoscale.inceptor/error fn) other :error handlers will be triggered from the stack, if you just return the context it will resume triggering :leave functions.

If the :error reaches the end of the stack without being handled, execute will throw it.

halt clj/s

(halt ctx)

Removes all remaining interceptors from context's execution queue and stack. This effectively short-circuits execution of Interceptors' :enter/:leave and returns the context

in clj/s

(in f path)

Modifies interceptor stage to take in specified path

into-stages clj/s

(into-stages chain stages f)

Applies fn f on all stages (collection of :enter, :leave and/or :error) of chain. This provides a way to apply middlewares to an entire interceptor chain at definition time.

Useful when used in conjunction with, after-stage, before-stage.

f will be a function of a stage function, such as the ones returned by before-stage, after-stage and an execution context. The stage function is a normal interceptor stage function, taking 1 or 2 args depending on stage of execution (enter/leave or error, error taking 2 args), can potentially be multi-arg if it has to be used for all stage types. The execution context is a map that will contain an :interceptor key with the value for the current interceptor and :stage to indicate which stage we're at (enter, leave or error).

`(into-stages [...] [:enter :error] (fn [stage-f execution-ctx] (after-stage stage-f (fn [...] ...))))

lens clj/s

(lens f path)

Modifies interceptor stage to take from path and return to path

out clj/s

(out f path)

Modifies interceptor stage to return at specified path

remove clj/s

(remove ctx pred)

Remove all interceptors matching predicate from stack/queue, returns context

terminate clj/s

(terminate ctx)

Removes all remaining interceptors from context's execution queue. This effectively short-circuits execution of Interceptors' :enter functions and begins executing the :leave functions.

transform clj/s

(transform f f')

Takes stage function, and wraps it with callback that will return a new context from the application of f' onto it. It can be useful to run a separate function after a stage returns and apply some transformation to it relative to the original context. f' takes the initial stage context and f realized return value as arguments.

when clj/s

(when f pred)

Modifies interceptor stage to only run on ctx if pred returns true'ish

xform clj/s

(xform ctx xf)

Takes a context from execution and run xf (transducing fn) on stack/queue, returns a new context

xform-queue clj/s

(xform-queue ctx xf)

Takes a context from execution and run xf (transducing fn) on queue, returns a new context

xform-stack clj/s

(xform-stack ctx xf)

Takes a context from execution and run xf (transducing fn) on stack, returns a new context