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Create a snapshot of a directory for use with memfs
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boneskull/snapshot-fs
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Create a snapshot of a directory for use with
memfs
I wanted something to help convert directories of test fixtures on-disk to a format usable by an in-memory filesystem (memfs).
To that end, thesnapshot-fs package ships a CLI,snapshot-fs, which converts a directory tree to aCompact JSON,CBOR orDirectoryJSON snapshot for use withmemfs.
- The command-line options have changed; seeUsage below.
- The default input/output format is now CJSON.
- CBOR snapshots are now supported.
- The
exportsubcommand got a--dry-runflag.
- The command-line options have changed; seeUsage below.
snapshot-fscan now re-create a directory on the filesystem from aJSON snapshot.loadSnapshot()is nowreadSnapshot()- Export functionality exposed via
exportSnapshot()
snapshot-fs requires Node.js v22.13.0 or newer.
snapshot-fs can be run vianpx snapshot-fs or installed globally vianpm install -g snapshot-fs. Or however else you want to consume it.
snapshot-fs exports both CommonJS and ES modules.
snapshot-fs [dest]Create memfs snapshot from filesystemCommands: snapshot-fs create [dest] Create memfs snapshot from filesystem [default] snapshot-fs export <snapshot> [dest] Export a JSON snapshot to the filesystemOutput: --separator, --sep Path separator [choices: "posix", "win32"] [default: "posix"] -f, --format Snapshot format [string] [choices: "cbor", "cjson", "json"] [default: "cjson"]Positionals: dest Path to output fileInput: -s, --source File or directory to snapshot [string] [default: (current directory)]Options: --version Show version number [boolean] --help Show help [boolean]For more information, visit https://github.com/boneskull/snapshot-fsWhen run without a subcommand,create will be invoked.
create w/Compact JSON Snapshots
By default (as of v5.0.0),snapshot-fs will create a snapshot inCJSON/Compact JSON format.
snapshot-fs --source /some/dir /path/to/output.json
This is equivalent to:
snapshot-fs create --source /some/dir /path/to/output.json --format=cjson
In your code, you can use the resulting file usingmemfs directly:
import{typeJsonUint8Array,typeSnapshotNode,fromJsonSnapshot}from'memfs/lib/snapshot/index.js';import{memfs}from'memfs';constdata=(awaitreadFile('/path/to/output.json',))asunknownasJsonUint8Array<SnapshotNode>;const{vol}=memfs()awaitfromJsonSnapshot(data,fs:vol.promises);console.log(vol.toTree());// ... do your thing
...or you can use thereadCJSONSnapshot() helper fromsnapshot-fs:
importtype{JsonUint8Array,SnapshotNode}from'memfs/lib/snapshot/index.js';import{readCJSONSnapshot}from'snapshot-fs';constdata=(awaitreadFile('/path/to/output.json',))asunknownasJsonUint8Array<SnapshotNode>;constvol=awaitreadCJSONSnapshot(data);console.log(vol.toTree());
This is fast;JSON.parse() is never called!
(but we can get faster...)
create w/CBOR Snapshots
Similar to the above, you can create a CBOR-formatted snapshot this way:
snapshot-fs --source /some/dir /path/to/output.json --format=cbor
In your code, you can use the resulting file usingmemfs directly:
import{typeSnapshotNode,fromBinarySnapshot}from'memfs/lib/snapshot/index.js';importtype{CborUint8Array}from'@jsonjoy.com/json-pack/lib/cbor/types.js';import{memfs}from'memfs';constdata=(awaitreadFile('/path/to/output.json',))asunknownasCborUint8Array<SnapshotNode>;const{vol}=memfs()awaitfromBinarySnapshot(data,fs:vol.promises);console.log(vol.toTree());// ... do your thing
...or you can use thereadCBORSnapshot() helper fromsnapshot-fs:
import{typeSnapshotNode,fromBinarySnapshot,}from'memfs/lib/snapshot/index.js';importtype{CborUint8Array}from'@jsonjoy.com/json-pack/lib/cbor/types.js';import{readCBORSnapshot}from'snapshot-fs';constdata=(awaitreadFile('/path/to/output.json',))asunknownasCborUint8Array<SnapshotNode>;constvol=awaitreadCBORSnapshot(data);console.log(vol.toTree());
Caution
DirectoryJSON is somewhat lossy and should be avoided if you ever want to re-create snapshots on yourreal filesystem (e.g., usingexport). For a directory full of text files, this is fine; for anything else, use CJSON or CBOR.
snapshot-fs --source /some/dir /path/to/output.json --format=json
This can be read into amemfsVolume like so:
import{readFile}from'node:fs/promises';import{memfs}from'memfs';constdirectoryJson=JSON.parse(awaitreadFile('/path/to/output.json','utf8'),);const{ vol}=memfs();vol.fromJSON(directoryJson);
This allows you to re-create a directory on the filesystem from a snapshot. Handy!
snapshot-fs export <snapshot> [dest]Export a JSON snapshot to the filesystemPositionals: snapshot Path to snapshot file (CBOR/CJSON/DirectoryJSON) [required] dest Destination directory [default: Current working directory]Output: --separator, --sep Path separator [choices: "posix", "win32"] [default: "posix"]Options: --version Show version number [boolean] --help Show help [boolean] -D, --dry-run Print what would be written to the filesystem [boolean] -f, --format Snapshot format [string] [choices: "cbor", "cjson", "json"] [default: "cjson"]If you have a snapshot (either format) and you want to re-create snapshot on the filesystem, use theexport subcommand:
snapshot-fsexport /path/to/snapshot.json /path/to/outputThe destination directory will be created if it doesn't exist.
Tip
Use the--dry-run flag withexport to see what would be written to the filesystem.
Some potentially-useful stuff exported fromsnapshot-fs:
createSnapshot()/createDirectoryJSONSnapshot()/createCJSONSnapshot()/createCBORSNapshot()- Create a JSON snapshot from a real or virtual FSreadSnapshot()/readDirectoryJSONSnapshot()/readCBORSnapshot()/readCJSONSnapshot()- Read a snapshot from a file and load it into a real or virtual FSexportSnapshot()- Alias forreadSnapshot()defaulting to the real FS
See the typings for more information.
Copyright 2024Christopher Hiller. Licensed Apache-2.0
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