It would be useful if, in addition to the requirements.txt format, pip-compile also had the option of outputting the requirements and what it knows about each requirement in a standard format like json. This would give users much greater ability to create custom requirements.txt files, without having to rely on fragile parsing of pip-compile's requirements.txt output.

The structured data could include things like:

• for each requirement:
  • the "via" values in a structured format
    • For example, if an annotation has an associated path, it can be included separately alongside as a relative path, and the base path can be included once at the top-level (see also Add an option to not include paths in annotations #1084).
  • the requirement's hashes (for --generate-hashes), as well as distinguishing the "exact" hash (e.g. for Provide a way to limit to a single hash per requirement when generating hashes #1330)
  • whether the requirement is "safe" in the sense of --allow-unsafe. This would give users more control over how unsafe requirements should be handled.
  • whether the requirement is hashable or editable. This would let users e.g. split off non-hashable dependencies into a separate file that doesn't use hashes.
  • the annotation line(s) as constructed by pip-compile (for convenience, since these would also be constructible manually from other data)
  • the requirement line(s) as constructed by pip-compile (for convenience, if the user would like to include them as is)

This feature would give users a way to address a number of issues in this tracker, in the absence of a fix in pip-tools. Here is a partial list:

• Provide a way to limit to a single hash per requirement when generating hashes #1330 ("Provide a way to limit to a single hash per requirement when generating hashes")
• Request: Compact annotations #1306 ("Compact annotations")
• pip-compile annotations should be relative to file they are in #1107 ("annotations should be relative to file they are in")
• Add an option to not include paths in annotations #1084 ("Add an option to not include paths in annotations")
• Ignore hashes for version control repositories #994 ("Ignore hashes for version control repositories")
• Allow to skip dependencies (--no-deps) for individual requirements #817 ("Allow to skip dependencies")
• Include comments from input files in output file #391 ("Include comments from input files in output file")
• Exclude package? #333 ("Exclude package?")
• allow overriding/forcing a certain version #215 ("allow overriding/forcing a certain version")