A small, strange building block. https://conduitry.dev/defiler
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The API consists of two classes, File and Defiler.

A File represents a physical file on the disk, or a virtual file with no particular corresponding file in the file system, or a partially or fully transformed physical or virtual file.

A Defiler represents a set of watched files on the disk, plus a set of virtual files, plus the operations to perform on them.

File

Constructor

new File()

A new File instance to serve as the representation of a physical file, a virtual file, or a transformed file.

Properties

path

The relative path to the file, from some understood root. The path is always separated by forward slashes, regardless of platform. Updating dir, filename, or ext also updates this.

dir

The directory (not including the trailing slash) containing the file. For top-level files, this is an empty string.

filename

The filename (including the extension) of the file.

ext

The extension (including the preceding .) of the file. For extension-less files, this is an empty string.

stats

The fs.Stats of the file.

bytes

The file's contents can be retrieved and updated by getting or setting bytes, which is a Buffer.

Don't mutate this property. This causes various unwanted effects. Instead, assign it a new Buffer instance.

text

The file's contents can also be retrieved and updated by getting or setting text, which is a string.

Reassigning the entire bytes or text properties will keep the other in sync.

enc

The assumed encoding for the file. Defaults to 'utf8'. Must be one of Node.js's supported encodings. Changing this in the middle of processing a file can cause confusing behavior, and is not recommended.

Defiler

Constructor

new Defiler({ dir, filter, read = true, enc = 'utf8', pre, watch = true, debounce = 10 }, ..., { transform, generators, resolver, onerror })

A new Defiler instance to represent a collection of physical files and virtual files, a transform to run on them, and additional generators. This constructor should be passed multiple arguments; all but the last one should be 'input configuration' objects, and the last should be an object containing transform and (optionally) generators, resolver and/or onerror.

  • Input configuration
    • dir - a directory to watch
      • filter({ path, stats }) - (optional) a function to decide whether a given file or directory should be considered by Defiler. It's passed an object containing the file or directory's relative path and its stats. It should return true or false (or a Promise resolving to one of those). Returning false for a directory means that none of its contents will be included. You can use stats.isFile() and stats.isDirectory() to determine whether this is a file or a directory
    • read - (optional) whether to actually read in the contents of the files in the directory. Defaults to true. If false, the files will still be run through the transform, but they will have null bytes and text
      • Can also be a function read({ path, stats }), which should return true or false (or a Promise resolving to one of those), allowing whether each file is read in to be decided individually
    • enc - (optional) encoding to use for files read in from the directory. Defaults to 'utf8'
      • Can also be a function enc({ path, stats, bytes }), which should return an encoding name (or a Promise resolving to one), allowing the encoding on each file to be decided individually
    • pre(file) - (optional) a function to run some very basic pre-processing specific to this transform before the file continues on to the common transform. file is an object containing path and stats. You can change the path value (perhaps adding a prefix) and can also add further custom fields that will exist on the file when it is passed to the transform. (It is this potentially modified path that will be used in defiler.get.) This allows you to (among other things) determine which directory a file came from when transforming it. The pre-processing function can return a Promise to indicate when it's done
    • watch - (optional) whether to actually watch the directory for changes. Defaults to true. If false, the files will still be run through the transform, but any changes to them will not be
      • debounce - (optional) length of timeout in milliseconds to use to debounce incoming events from fs.watch. Defaults to 10. Multiple events are often emitted for a single change, and events can also be emitted before fs.stat reports the changes. Defiler will wait until debounce milliseconds have passed since the last fs.watch event for a file before handling it. The default of 10ms Works On My Machine
  • Transform/generator/resolver configuration
    • transform({ file, event }) - a transform function, which is passed an object containing the File instance to mutate and an event string indicating why this file is being run through the transform. This event can be 'read' (indicating the file was just read in from the disk), 'add' (indicating it was just manually added by calling defiler.add), 'delete' (indicating it's a file that was just deleted from the disk), or 'retransform' (indicating the file is unchanged but is being re-transformed because one of its dependencies changed). The transform function can return a Promise to indicate when it's done
    • generators - (optional) an array of generator functions, each of the form generator(). Each generator is called without arguments, and can return a Promise to indicate when it's done
    • resolver(base, path) - (optional) a function that will be used to resolve the paths passed to defiler.get and defiler.add from the transform. This will be passed two arguments, base (the path of the file being transformed) and path (the path passed to defiler.get/defiler.add), and should return the resolved path to use
    • onerror(error) - (optional) a function that will be called with an error object whenever an error occurs. See Errors below.

Properties

paths

A Set of the original relative paths of all of the physical files. (This does not include virtual files.) This will be available by the time your transform or generators are called, even if not all of the individual files have been read in yet.

files

A Map of original relative paths to File instances for the transformed files. (This includes physical and virtual files.) During the initial wave of processing, this will only contain the files that are done being transformed.

Methods

exec()

Start the Defiler running.

Returns a Promise that resolves when the initial wave of processing is complete.

get(path)

Wait for a file to be ready and retrieve the File instance.

  • path - the path to wait for to become available and to then return

Returns a Promise resolving to the File instance.

This can be asked for a physical or virtual file. If you ask for a file during the initial wave of processing before it is available, Defiler will wait for the file to be ready and transformed. If it ever happens that every in-progress file is waiting for a file to become available, the deadlock will be broken by Defiler resolving all of the pending Files to undefined. This may happen multiple times during the initial wave of processing.

When used in your transform, this will also register the file being transformed as depending on the file at path. Once the initial wave of processing is complete, any changes to dependencies will cause their dependents to be re-transformed. When used in a generator, this will register the generator as depending on the file at path, and any changes to dependencies will cause the generator to be re-run.

get(paths)

Wait for multiple files to be ready and retrieve the File instances.

  • paths - the array of paths to wait for to become available and to then return

Returns a Promise resolving to an array of File instances.

get(filter)

Wait for all files whose paths match a given filter function and retrieve the File instances.

  • filter(path) - a function that will be passed a path and should return a boolean

Returns a Promise resolving to an array of matching File instances, sorted by their (original) paths.

This will return physical and virtual files. Once the initial wave of processing is complete, any new files matching the filter will also cause the generator or transform to be re-run.

add(file)

Manually insert a virtual File, running it through the transform.

  • file - the file data of the virtual file to add

The object does not need to be a File instance, and in fact there is no benefit to doing so. A new File instance is always created with properties Object.assigned from file.

resolve(path)

Resolves a path from the file being transformed, using your specified resolver.

  • path - the path to resolve

Returns the resolved path.

If you did not specify a resolver or if you are currently in a generator, this will be path unchanged.

Errors

The object passed to your onerror callback will be of two forms, depending on whether it is the result of an error thrown by the transform or an error thrown by a generator.

Transform errors: { file, event, error }

When an error occurs in the transform, onerror is called with an object containing the File instance that caused the error, the event that was passed to the transform, and the thrown error.

Generator errors: { generator, error }

When an error occurs in a generator, onerror is called with an object containing the generator function that threw the error and the thrown error.