cherry

General-purpose build system

npm install cherry
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Cherry

Cherry is a general-purpose build cook tool. It provides a CoffeeScript-based DSL for defining recipes.

Cherry takes a file (a Cherryfile, Cakefile or cherry.coffee) with recipes and turns input files in current directory to output files.

Main features:

  • a friendly CoffeeScript-based DSL
  • allows to write very custom build flows while being terse and declarative
  • automatic dependencies resolution
  • watch mode
  • pattern matching between input and output paths
  • asynchronous operation (while supporting synchronous operation as well)
  • flow library that eases composition of build steps

Installation

Install from npm with -g switch to put it in the $PATH.

npm install -g cherry

Usage

Supported commands for cherry are listed when none is given.

PS> cherry
No command given. Need at least one of those:

  clean         Deletes all targets
  build         Builds all targets
  watch         Watches all inputs and rebuilds outdated targets
  dump          Print the dependency tree

Commands can be chained in any combination, for example cherry clean build watch. Mind that watch is supposed to be always the last one because it never ends (only when the process is killed by Ctrl+C).

Recipes

A recipe looks like this:

recipe
  in:  'src/*.coffee'
  out: 'lib/*.js'
  run: (flow (read 'utf8'), (compile coffee.compile), (save 'utf8'))

A recipe have three mandatory parts: in, out and run fields.

in field

in it's a pattern of input files paths. Current directory is scanned for files that matches this pattern. * marks a wild card group.

out field

out tells what will be produced (a target) from matched input file(s). It can contain wild card groups as well. Wild card groups are matched against corresponding groups in in pattern in a manner similar to replace method of strings, in the upper example file src/cherry.coffee will produce lib/cherry.js file.

A shortage of groups in output pattern indicates a will to produce one target from many files. For example this recipe will make app.js of many *.coffee files.

recipe
  in:  'src/*.coffee'
  out: 'app.js'
  run: (flow (read 'utf8'), (compile coffee.compile), (join '\n'), (save 'utf8'))

The rule here is that all input paths that matches the same target are grouped as that target's dependencies. All of them will be passed to function given at run field. You can a little more crazy things like this (run field as above):

recipe
  in:  'src/*/*.coffee'
  out: 'src/*.js'

This will produce one *.js file for each subdirs of src dir. (Where the name of file before .js is name of that dir.)

run field & run interface

run field is a function that will produce a result for a recipe. It is once called for every target and have to accept following arguments:

run: (input_paths, callback) ->

input_paths is an array of all paths of all dependencies for current target. callback is a function of one optional argument err that needs to be called after completion of building the target. err needs to be an error information and only passed on failure.

Any exceptions thrown by run function will be treated the same as passing an error to callback. (So catching exception inside of run is not necessary).

Using callback instead of return value enables asynchronous operation which is much appreciated (allows interleaving building of multiple targets).

run function is called with this field set to a clone of a target object. Each target (a matched output path) has one object of that kind and is composed of the same fields that are printed by cherry dump:

  • path -- matched target's output path
  • recipe -- recipe for that target
  • deps -- array of dependencies paths
  • nexts -- array of target paths that depend on this one
  • awaiting -- array of dependencies that need to be build before this one can start (it's actually empty when run is called)

run function is supposed not to change any of these fields but can add new.

For further reference, the arguments and the behaviour mentioned here are called the "run interface".

dep field

and field

Interdependencies & Caching

Cherry manages interdependencies automatically. If any target depends on any other, then that dependency will be built first. This works also in watch mode: rebuilding a target triggers rebuilding of all others dependent on it.

Actually saving intermediate targets to disk is not necessary. Successful build of a target is not marked when file is saved but when callback given to run is called. You can cache result in memory and retrieve it later without disk operation. (This can speed up things significantly but also increase memory consumption tremendously so do it with care.)

Caching makes sense even more on watch mode. If you only use cherry build then all unsaved targets will be built causing a rebuild of all targets that depend on them.

Flow Library

Flow is a library of functions that are meant to ease asynchronous processing of files that take many steps to complete. Each of them either is a function that complies with run function interface or returns one.

In the Flow library this interface is a little enhanced in that callbacks additionally to err receive also data argument.

Two most significant functions are flow and do_all. First allows to queue functions and call them in order while the second calls one function across an array of data simultaneously and collect results to new array.

flow function

flow = (steps...) -> (data, final_callback) ->

Function returned by flow executes all steps in order while passing data between them. Each step receives data from previous step and is required to pass (after err argument) new data to the callback given to it. (Steps have to be compatible with the run interface.)

First step is called with data passed to the resulting function. final_callback is called with data (after err argument) that was returned (passed to it's callback) by the last step.

do_all function

do_all = (iterator) -> (data, callback) ->

Returned function will invoke the iterator (complying with run interface) once for every element of data array, collect all results to an array an invoke callback with this array.

Indexes of input data are kept in output data arrangement.

read function

read = (encoding) -> (input_paths, callback) ->

Returned function reads all input files using optional encoding. If no encoding is given then Buffer objects are created instead of strings.

If given path was saved using remember function then remembered value is used instead of reading from file system.

save function

save = (encoding) -> (data, callback) ->

Returned function saves the first element of data to path pointed in this.path. To save all elements of data use join function.

remember function

remember = (data, callback) ->

Remembers data[0] in memory using path from this.path. Further reads using read on that path will retrieve the remembered value. The value can be any object.

join function

join = (glue = '\n') -> (data, callback) ->

Returned function joins all elements of data with glue as in data.join(glue).

compile function

compile = (compiler, args...) -> (sources, callback) ->

Returns a wrapper for a synchronous compiler. For each element of sources compiler will be called with source, args... arguments. Returned values are in an array to next step.

take function

take = (amount) -> (data, callback) ->

Returned function limits the number of elements in data to amount of elements.

filter function

filter = (pattern) -> (data, callback) ->

Returned function filters elements of data using pattern. The pattern can be a one-param function returning a bool, a RegExp or a string. If it's a string then it's works like the in field patterns of recipes.

Spawning Processes

For spawning auxiliary processes you can use the standard node-wise method or the spawn function.

spawn = (command, args, callback) ->

command is the system command to invoke, args is an array of arguments and callback takes following arguments:

(code, stdout, stderr)

code is the exit code returned by application, stdout is a string with all stdout output from application and stderr is all stderr output from application.

For convenience there's the spawn.default handler that wraps given callback and returns a function that will print the stdout invoke this callback with an error message from stderr if code is different than 0.

spawn.default = (callback) -> (code, stdout, stderr) ->

Licence

MIT, see the COPYING file.

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