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Lens based Haskell refactoring toolkit.


Study after study shows that the very best designers produce structures that are faster, smaller, simpler, clearer, and produced with less effort. The differences between the great and the average approach an order of magnitude.

  • Fred Brooks


Refactorio - Optical Refactoring Tool

Usage: refactorio [--io] EXPR [-t|--target TARGET] [-g|--glob GLOB]
                  [--prelude MODULE] ([-a|--ask] | [-p|--preview] |
                  [-m|--modify] | [--review] | [-s|--search]) ([--haskell|--hs]
                  | [--html] | [--javascript|--js] | [--c] | [--json] | [--xml]
                  | [--yaml])

Available options:
  --io                     Add IO to expr type ('ByteString -> IO ByteString')
  EXPR                     A Haskell expression of type 'ByteString ->
  -t,--target TARGET       One or more files/directories to traverse (defaults
                           to stdin, use '-' to force stdin)
  -g,--glob GLOB           Glob matches to include (eg '*.ini', 'f??b?r.c')
  --prelude MODULE         Use a specific Prelude module
  -a,--ask                 Ask before changing files (default)
  -p,--preview             Only show the changes that would be made
  -m,--modify              Make the changes and summarize changed filenames
  --review                 Make the changes and show details of changes
  -s,--search              Activate alternate search mode (Haskell mode only
                           right now)
  --haskell,--hs           Include .hs files and make Haskell ops available
  --html                   Include .htm(l) files and make XML ops available
  --javascript,--js        Include .js files and make JavaScript ops available
  --c                      Include .c files and make C ops available
  --json                   Include .json files and make JSON ops available
  --xml                    Include .xml files and make XML ops available
  --yaml                   Include .y(a)ml files and make YAML ops available
  -h,--help                Show this help text

Major Modes

In all modes Refactorio traverses one or more files executing a ByteString -> ByteString function on them. For a given file if the function does not change the input then no output is logged for that file. If the function does change the file then what happens next is dependent on the mode.

Any ByteString -> ByteString function definition will work, for example:


BS.take 1024

over convert Text.toUpper

# or equivalently
convert %~ Text.toUpper

key "foo" . _Number *~ 3

Ask Mode (-a / --ask)

This is the default mode. In this mode Refactorio will show you the changes that it's about to make and prompt you on a file by file basis whether you want to accept the changes or not. If you accept, the file will be replaced, if not the file will be left intact (or you can 'Q'uit at any time).

Preview Mode (-p / --preview)

not touch any files. You can think of it sort of like a --dry-run. In this mode Refactorio will just show all the changes that it would make, but

Review Mode (-r / --review)

In this mode Refactorio will make changes to all files without asking but will show the full set of changes as they are made.

Modify Mode (-m / --modify)

This is basically a --quiet style mode that makes all changes without confirmation and just reports which files changed with no further details.

Search Mode (-s / --search)

This is a special mode which currently only works with haskell-src-exts(-prisms) which provide SrcSpanInfos which represent the portion of the source code that a given feature occupies. This mode can be easily made to work with any other lenses that can provide access to similar information and we are exploring ways to broaden it's usefulness further.


Here are a few examples to whet your appetite. For more see examples.

JSON (via lens-aeson):

"Upper case the string values of the array found under ''."

JSON Example

YAML (same operators):

"Multiply the value of the key 'version' by 32."

YAML Example

HTML (via xml-html-conduit-lens)

TODO: Find a good way to deal with HTML.  (problems with each of `hexpat-lens`, `hexml-lens`, `xml-html-conduit-lens` and `xml-lens`)

XML (also via xml-html-conduit-lens)

C'mon, you've never needed to "find all the authors with names longer than 15 characters and then sort all of the letters in their name that are above 'm' in place?" Pshaw.

XML Example

Regex (via lens-regex):

Drop regex's in anywhere you like, eg. "uppercase and reverse the characters in the value of the JSON object at this key that match this regular expression":

Regex Example

Compressed Files (via zlib-lens):

Reach inside eg. gzipped files and do what you gotta do:

Example is temporarily unavailable, but goes something like:

refactorio -t foo.json.gz --json 'convert . from Z.gzipped . from convert . key \"baz\" . _Number *~ 85'

Type Conversions

The beginnings of convert and convertTo/convertFrom (along with a/an) exist which can be used like so:

When types can be infered:

% refactorio --html -t /tmp/voltron/src 'convert %~ Text.toUpper'

When types have to be clarified:

% refactorio --html -t /tmp/voltron/src 'convertTo(a::LByteString) %~ Text.toUpper'

Haskell (via haskell-src-exts and haskell-src-exts-prisms):

TODO: revamp after re-wiring

Try these on your projects:

refactorio --haskell _Module.biplate._ModuleName.end
refactorio --haskell _Module.biplate._Int.end
refactorio --haskell _Module.biplate._String.end
refactorio --haskell _Module.biplate._FieldUpdate.end
refactorio --haskell _Module.biplate._Frac.end
refactorio --haskell '_Module.biplate._Int.filtered(odd.view target).end'
refactorio --haskell '_Module.biplate._Int.filtered(even.view target).end'
refactorio --haskell '_Module.biplate._Int.filtered((>10).view target).end'

There are more examples here.


For now the easiest way to get it working is to stack install . in this directory. Then commands like this should work:

refactorio --json 'key "foo" . key "bar" . _Number *~ 15' -t ./examples


cat Somefile.hs | refactorio -s --haskell _Module.biplate._ModuleName.end -

(where the -t/--target is a file or directory to process and can be outside of the refactorio project root).


In addition to the general warning about this being alpha quality software, no work has been done on performance and in fact in some cases even reasonable performance has been sacrificed in the name of expediency.

In some places I've resorted to outright hacks, such as when parsing YAML by reading it as YAML, writing it as JSON for processing it with lens-aeson, then converting it back.

In addition to being slow some of these tricks will do things like cause a file to be reformatted by the serialization round-trip even if your function doesn't make an actual semantic change.

Configurable Format-specific Preludes

Refactorio has a hardcoded set of qualified imports which you can find somewhere around here.

Currently the only unqualified import that Refactorio mandates is Text.Regex.Quote which brings the r QuasiQuoter into scope.

In addition Refactorio attempts to load a single "Prelude" which can bring unqualified names into scope. Various lens packages for different formats have conflicting imports (eg. _String in lens-aeson and in haskell-src-exts-prisms) so to avoid conflicts for now if you pass a "special mode" flag (eg. --haskell, --json, etc) Refactorio will attempt to use Refactorio.Prelude.{ModeName} (eg Refactorio.Prelude.Haskell, etc). If no special mode is provided, Refactorio.Prelude.Basic is used.

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Refactorio is a tool with which you build and maintain software.




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