cabal.md

Cabal

Project Discovery

Find all directories with a cabal.project file or a file with a .cabal extension. When one is found, skip all subdirectories.

NOTE: We don't actually examine the cabal files, we just use their existence to determine that we are woking with a cabal project. As a result, we can handle multiple *.cabal files, even though cabal cannot.

Analysis

From the project root, we open the ./dist-newstyle/cache/plan.json file, created by cabal. The relevant items in the file take the following form:

Extra data removed for brevity

{
    "install-plan": [
        {
            "type": "configured",
            "id": "with-components-1.0.2.3-efgh",
            "pkg-name": "with-components",
            "pkg-version": "1.0.2.3",
            "style": "global",
            "components": {
                "lib": {
                    "depends": [
                        "base-4.13.0.0"
                    ]
                },
                "setup": {
                    "depends": [
                        "rts"
                    ]
                }
            }
        },
        {
            "type": "pre-existing",
            "id": "rts",
            "pkg-name": "rts",
            "pkg-version": "1.0",
            "depends": []
        },
        {
            "type": "configured",
            "id": "spectrometer-0.1.0.0-inplace",
            "pkg-name": "spectrometer",
            "pkg-version": "0.1.0.0",
            "style": "local",
            "depends": [
                "aeson-1.5.2.0-abcd",
                "base-4.13.0.0",
                "with-components-1.0.2.3-efgh"
            ]
        }
    ]
}

Analysis has two notable parts: matching id fields from the strings in depends and components.*.depends, and noting the package type and style. pre-existing types refer to builtin, ghc-provided packages, while configured packages have two styles of their own: local, referring to the current project, and global, referring to packages obtained from a remote source like hackage.