Edit

Configuration Files

TOML Format

You can configure comby to run a suite of patterns in a single file. The file format uses TOML. Here is an example file that contains two rewrite patterns:

[my-first-pattern]

match="Array.prototype.slice.call(:[arguments]);"

rewrite="Array.from(:[arguments])"

[my-second-pattern]
# A multiline example.

match='''
function :[[fn]](:[1], :[2]) {
  :[body]
};'''

rewrite='''
function :[[fn]](:[2], :[1]) {
  :[body]
};'''

rule='where :[fn] != "divide"'

Start a pattern by giving it a section name like [my-first-pattern]. You can add as many patterns as you like, but each name must be unique in the file. Multiple patterns are run in alphabetical order by name.

After each section like [my-first-pattern], you should specify:

  • match=... for the match template
  • rewrite=... for the rewrite template
  • rule=... (optional) valid rule

Like the example above, the templates should be quoted. Use triple quotes for multiline templates. Use a single ' or ''' to avoid escaping double quotes, as done for rule=... above.

Over time, the configuration file will allow more options and flags. If you have a special request, please create an issue.

Running

You can run the above configuration on the contents below. For example, put the following in a file in.js where you will run comby:

Array.prototype.slice.call(arguments);

function multiply(x, y) {
  return x * y;
};

function divide(x, y) {
  return x / y;
};

Create a file to store your patterns. For example, place the above contents in a file like comby.toml. Run it on a set of files that have the .js extension like this:

comby -config comby.toml -f .js

Currently, it’s important to use the -f option for filtering files when using -config, or comby will think it is an anonymous argument for a command line template. Subcommands will help resolve this issue.

You can add additional flags, like -i, -exclude, -matcher and so on, as usual.

It’s possible to specify more than one config file, for example:

comby -config one.toml,two.toml,three.toml -f .js

However, all pattern names must be unique across all of these files.

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