Transcribe

Transcribe is a simple program which generates Markdown documentation from code comments.

The general idea is that each "export" should be accompanied by a "docstring". The first line of the "docstring" should be a Haskell-inspired type signature in the form <heading-prefix> <name> :: <type>.

//# map :: (a -> b) -> Array a -> Array b
//.
//. Transforms a list of elements of type `a` into a list of elements
//. of type `b` using the provided function of type `a -> b`.
//.
//. ```javascript
//. > map (String) ([1, 2, 3, 4, 5])
//. ['1', '2', '3', '4', '5']
//. ```
function map(f) {
  return function(xs) {
    var output = [];
    for (var idx = 0; idx < xs.length; idx += 1) {
      output.push (f (xs[idx]));
    }
    return output;
  };
}

The --heading-prefix option specifies which lines in the source files contain type signatures to become headings in the output. The default value is //#; specify a different value if using a different comment style. For example:

--heading-prefix '#%'

The --prefix option specifies which lines in the source files should appear in the output along with the lines prefixed with <heading-prefix>. The default value is //.; specify a different value if using a different comment style. For example:

--prefix '#.'

Each line beginning with zero or more whitespace characters followed by the prefix is included in the output, sans prefix and leading whitespace. The . in the default prefix makes it possible to be selective about which comments are included in the output: comments such as // Should never get here! will be ignored.

The --url option specifies a template for generating links to specific lines of source code on GitHub or another code-hosting site. The value should include {filename} and {line} placeholders to be replaced with the filename and line number of each of the signature lines. For example:

--url 'https://github.com/plaid/sanctuary/blob/v0.4.0/{filename}#L{line}'

Avoid pointing to a moving target: include a tag name or commit hash rather than a branch name such as master.

The --heading-level option specifies the heading level, an integer in range [1, 6]. The default value is 3, which corresponds to an <h3> element in HTML. Specify a different value if desired. For example:

--heading-level 4

The --insert-into option specifies the name of a file into which Transcribe will insert the generated output. By default, Transcribe writes to stdout. However, if --insert-into is provided, Transcribe will insert the output in the specified file between two special tags: <!--transcribe--> and <!--/transcribe-->. For example:

--insert-into README.md

The options should be followed by one or more filenames. The filenames may be separated from the options by --. Files are processed in the order in which they are specified.

Here's a complete example:

$ transcribe \
>   --url 'https://github.com/plaid/example/blob/v1.2.3/{filename}#L{line}' \
>   -- examples/fp.js
### <a name="map" href="https://github.com/plaid/example/blob/v1.2.3/examples/fp.js#L3">`map :: (a -⁠> b) -⁠> Array a -⁠> Array b`</a>

Transforms a list of elements of type `a` into a list of elements
of type `b` using the provided function of type `a -> b`.

```javascript
> map (String) ([1, 2, 3, 4, 5])
['1', '2', '3', '4', '5']
```

### <a name="filter" href="https://github.com/plaid/example/blob/v1.2.3/examples/fp.js#L23">`filter :: (a -⁠> Boolean) -⁠> Array a -⁠> Array a`</a>

Returns the list of elements which satisfy the provided predicate.

```javascript
> filter (function(n) { return n % 2 === 0; }) ([1, 2, 3, 4, 5])
[2, 4]
```

By default, the output is written to stdout. One could redirect it to a file to generate lightweight API documentation:

$ printf '\n## API\n\n' >>README.md
$ transcribe \
>   --url 'https://github.com/plaid/example/blob/v1.2.3/{filename}#L{line}' \
>   -- examples/fp.js >>README.md

Reading from stdin is not currently supported.

One could also insert the output into an existing file by providing the --insert-into option:

$ transcribe \
>   --url 'https://github.com/plaid/example/blob/v1.2.3/{filename}#L{line}' \
>   --insert-into README.md
>   -- examples/fp.js