improve Prolog vs. IDL detection (.pro files)

[slayoo]

Apparently some .pro files are detected as Prolog, while others are given the IDL label.
The latter is related with the IDL/GDL/PV-WAVE language family.

In the GDL project, all .pro files are IDL source code, while they fall in both categories according to github:

• https://github.com/gnudatalanguage/gdl/search?l=prolog
• https://github.com/gnudatalanguage/gdl/search?l=IDL

Would be great to improve consistency (i.e., so that all are detected as IDL).

Likely relevant helper info:
https://github.com/blackducksoftware/ohcount/blob/master/src/parsers/idl_pvwave.rl

HTH,
Sylwester (originaly reported by @EdwardEisenhauer)

[lildude]

The .pro extension is associated with quite a few different languages and thus relies upon the heuristic:

https://github.com/github/linguist/blob/1df78c248cafa6b414651673846e26e388710df9/lib/linguist/heuristics.yml#L378-L391

... and samples to identify the language based on the content so in order to make things more consistent, we'd need to improve the heuristics and add a few more representative samples.

Please feel free to open a PR to help improve things.

[slayoo]

So the current rules are as follows:

- extensions: ['.pro']
  rules:
  - language: Proguard
    pattern: '^-(include\b.*\.pro$|keep\b|keepclassmembers\b|keepattributes\b)'
  - language: Prolog
    pattern: '^[^\[#]+:-'
  - language: INI
    pattern: 'last_client='
  - language: QMake
    and:
    - pattern: HEADERS
    - pattern: SOURCES
  - language: IDL
pattern: '^\s*function[ \w,]+$'

[slayoo]

Some notes:

• all IDL files in https://github.com/github/linguist/tree/master/samples/IDL include function definitions, which is not that representative as IDL files may be pure scripts, may contain procedure definitions, ...
• QMake detection can be improved by including the mandatory "+=" chars along with HEADERS and SOURCES (which are also valid IDL code elements), see: https://github.com/blackducksoftware/ohcount/blob/3f1becb7181aa450ed2ec2539cc0c608f062b44c/src/detector.c#L951