leporello-js/src/runtime.js

/*
Converts generator-returning function to promise-returning function. Allows to
have the same code both for sync and async. If we have only sync modules (no
toplevel awaits), then code executes synchronously, and if there are async
modules, then code executes asynchronoulsy, but we have syntactic niceties of
'yield', 'try', 'catch'
*/
const gen_to_promise = gen_fn => {
  return (...args) => {
    const gen = gen_fn(...args)
    const next = result => {
      if(result.done){
        return result.value
      } else {
        // If promise
        if(result.value?.then != null) {
          return result.value.then(
            value => next(gen.next(value)),
            error => next(gen.throw(error)),
          )
        } else {
          return next(gen.next(result.value))
        }
      }
    }
    return next(gen.next())
  }
}

export const run = gen_to_promise(function*(module_fns, cxt){
  let calltree

  apply_promise_patch(cxt)

  for(let {module, fn} of module_fns) {
     cxt.found_call = null
     cxt.children = null
     calltree = {
       toplevel: true, 
       module,
       id: cxt.call_counter++
     }

     try {
       cxt.modules[module] = {}
       yield fn(cxt, __trace, __trace_call, __do_await)
       calltree.ok = true
     } catch(error) {
       calltree.ok = false
       calltree.error = error
     }
     calltree.children = cxt.children
     if(!calltree.ok) {
       break
     }
  }

  cxt.is_recording_deferred_calls = true
  const _logs = cxt.logs
  cxt.logs = []
  cxt.children = null

  remove_promise_patch(cxt)

  cxt.searched_location = null
  const call = cxt.found_call
  cxt.found_call = null

  return {
    modules: cxt.modules,
    calltree,
    call,
    logs: _logs,
    eval_cxt: cxt,
  }
})

const apply_promise_patch = cxt => {

  cxt.promise_then = cxt.Promise.prototype.then

  cxt.Promise.prototype.then = function then(on_resolve, on_reject) {

    if(cxt.children == null) {
      cxt.children = []
    }
    let children_copy = cxt.children

    const make_callback = (cb, ok) => typeof(cb) != 'function'
      ? cb
      : value => {
          if(this.status == null) {
            this.status = ok ? {ok, value} : {ok, error: value}
          }
          const current = cxt.children
          cxt.children = children_copy
          try {
            return cb(value)
          } finally {
            cxt.children = current
          }
        }

    return cxt.promise_then.call(
      this,
      make_callback(on_resolve, true),
      make_callback(on_reject, false),
    )
  }
}

const remove_promise_patch = cxt => {
  cxt.Promise.prototype.then = cxt.promise_then
}

const set_record_call = cxt => {
  for(let i = 0; i < cxt.stack.length; i++) {
    cxt.stack[i] = true
  }
}

const do_expand_calltree_node = (cxt, node) => {
  if(node.fn.__location != null) {
    // fn is hosted, it created call, this time with children
    const result = cxt.children[0]
    result.id = node.id
    result.children = cxt.prev_children
    result.has_more_children = false
    return result
  } else {
    // fn is native, it did not created call, only its child did
    return {...node, 
      children: cxt.children,
      has_more_children: false,
    }
  }
}

export const do_eval_expand_calltree_node = (cxt, node) => {
  cxt.is_recording_deferred_calls = false
  cxt.children = null
  try {
    if(node.is_new) {
      new node.fn(...node.args)
    } else {
      node.fn.apply(node.context, node.args)
    }
  } catch(e) {
    // do nothing. Exception was caught and recorded inside '__trace'
  }
  cxt.is_recording_deferred_calls = true
  return do_expand_calltree_node(cxt, node)
}


/*
  Try to find call of function with given 'location'

  Function is synchronous, because we recorded calltree nodes for all async
  function calls. Here we walk over calltree, find leaves that have
  'has_more_children' set to true, and rerunning fns in these leaves with
  'searched_location' being set, until we find find call or no children
  left.

  We dont rerun entire execution because we want find_call to be
  synchronous for simplicity
*/
export const do_eval_find_call = (cxt, calltree, location) => {
  // TODO remove
  if(cxt.children != null) {
    throw new Error('illegal state')
  }

  const do_find = node => {
    if(node.children != null) {
      for(let c of node.children) {
        const result = do_find(c)
        if(result != null) {
          return result
        }
      }
      // call was not find in children, return null
      return null
    }


    if(node.has_more_children) {
      try {
        if(node.is_new) {
          new node.fn(...node.args)
        } else {
          node.fn.apply(node.context, node.args)
        }
      } catch(e) {
        // do nothing. Exception was caught and recorded inside '__trace'
      }

      if(cxt.found_call != null) {
        return {
          node: do_expand_calltree_node(cxt, node),
          call: cxt.found_call,
        }
      } else {
        cxt.children = null
      }
    }

    // node has no children, return null
    return null
  }

  cxt.is_recording_deferred_calls = false
  cxt.searched_location = location

  const result = do_find(calltree)

  cxt.children = null
  cxt.searched_location = null
  cxt.found_call = null
  cxt.is_recording_deferred_calls = true

  return result
}

const __do_await = async (cxt, value) => {
  // children is an array of child calls for current function call. But it
  // can be null to save one empty array allocation in case it has no child
  // calls. Allocate array now, so we can have a reference to this array
  // which will be used after await
  if(cxt.children == null) {
    cxt.children = []
  }
  const children_copy = cxt.children
  if(value instanceof cxt.Promise) {
    cxt.promise_then.call(value,
      v => {
        value.status = {ok: true, value: v}
      },
      e => {
        value.status = {ok: false, error: e}
      }
    )
  }
  try {
    return await value
  } finally {
    cxt.children = children_copy
  }
}

const __trace = (cxt, fn, name, argscount, __location, get_closure) => {
  const result = (...args) => {
    if(result.__closure == null) {
      result.__closure = get_closure()
    }

    const children_copy = cxt.children
    cxt.children = null
    cxt.stack.push(false)

    const is_found_call =
      (cxt.searched_location != null && cxt.found_call == null)
      &&
      (
        __location.index == cxt.searched_location.index
        &&
        __location.module == cxt.searched_location.module
      )

    if(is_found_call) {
      // Assign temporary value to prevent nested calls from populating
      // found_call
      cxt.found_call = {}
    }

    let ok, value, error

    const is_toplevel_call_copy = cxt.is_toplevel_call
    cxt.is_toplevel_call = false

    try {
      value = fn(...args)
      ok = true
      if(value instanceof cxt.Promise) {
        set_record_call(cxt)
      }
      return value
    } catch(_error) {
      ok = false
      error = _error
      set_record_call(cxt)
      throw error
    } finally {

      cxt.prev_children = cxt.children

      const call = {
        id: cxt.call_counter++,
        ok,
        value,
        error,
        fn: result,
        args: argscount == null 
          ? args
          // Do not capture unused args
          : args.slice(0, argscount),
      }

      if(is_found_call) {
        cxt.found_call = call
        set_record_call(cxt)
      }

      const should_record_call = cxt.stack.pop()

      if(should_record_call) {
        call.children = cxt.children
      } else {
        call.has_more_children = cxt.children != null && cxt.children.length != 0
      }
      cxt.children = children_copy
      if(cxt.children == null) {
        cxt.children = []
      }
      cxt.children.push(call)

      cxt.is_toplevel_call = is_toplevel_call_copy

      if(cxt.is_recording_deferred_calls && cxt.is_toplevel_call) {
        if(cxt.children.length != 1) {
          throw new Error('illegal state')
        }
        const call = cxt.children[0]
        cxt.children = null
        const _logs = cxt.logs
        cxt.logs = []
        cxt.on_deferred_call(call, cxt.calltree_changed_token, _logs)
      }
    }
  }

  Object.defineProperty(result, 'name', {value: name})
  result.__location = __location
  return result
}

const __trace_call = (cxt, fn, context, args, errormessage, is_new = false) => {
  if(fn != null && fn.__location != null && !is_new) {
    // Call will be traced, because tracing code is already embedded inside
    // fn
    return fn(...args)
  }

  if(typeof(fn) != 'function') {
    throw new TypeError(
      errormessage 
      + ' is not a ' 
      + (is_new ? 'constructor' : 'function')
    )
  }

  const children_copy = cxt.children
  cxt.children = null
  cxt.stack.push(false)

  // TODO: other console fns
  const is_log = fn == console.log || fn == console.error

  if(is_log) {
    set_record_call(cxt)
  }

  let ok, value, error

  try {
    if(!is_log) {
      if(is_new) {
        value = new fn(...args)
      } else {
        value = fn.apply(context, args)
      }
    } else {
      value = undefined
    }
    ok = true
    if(value instanceof cxt.Promise) {
      set_record_call(cxt)
    }
    return value
  } catch(_error) {
    ok = false
    error = _error
    set_record_call(cxt)
    throw error
  } finally {

    cxt.prev_children = cxt.children

    const call = {
      id: cxt.call_counter++,
      ok,
      value,
      error,
      fn,
      args,
      context,
      is_log,
      is_new,
    }
    
    if(is_log) {
      // TODO do not collect logs on find_call?
      cxt.logs.push(call)
    }

    const should_record_call = cxt.stack.pop()

    if(should_record_call) {
      call.children = cxt.children
    } else {
      call.has_more_children = cxt.children != null && cxt.children.length != 0
    }

    cxt.children = children_copy
    if(cxt.children == null) {
      cxt.children = []
    }
    cxt.children.push(call)
  }
}