Why do stable and installed versions not match?

[sidekick-eimantas]

Hi

I'm doing some integration work with homebrew and am running into an odd problem.
brew info openjdk@11 --json=v2 and brew info ruby --json=v2 versions.stable and installed.version don't match.
Example output for brew info ruby --json=v2:

{
  "formulae": [
    {
      "name": "ruby",
      "full_name": "ruby",
      "tap": "homebrew/core",
      "oldname": null,
      "aliases": [
        "ruby@3",
        "ruby@3.1"
      ],
      "versioned_formulae": [
        "ruby@3.0",
        "ruby@2.7",
        "ruby@2.6",
        "ruby@2.5",
        "ruby@2.4"
      ],
      "desc": "Powerful, clean, object-oriented scripting language",
      "license": "Ruby",
      "homepage": "https://www.ruby-lang.org/",
      "versions": {
        "stable": "3.1.2",
        "head": "HEAD",
        "bottle": true
      },
      "urls": {
        "stable": {
          "url": "https://cache.ruby-lang.org/pub/ruby/3.1/ruby-3.1.2.tar.gz",
          "tag": null,
          "revision": null,
          "checksum": "61843112389f02b735428b53bb64cf988ad9fb81858b8248e22e57336f24a83e"
        }
      },
      "revision": 1,
      "version_scheme": 0,
      "bottle": {
        "stable": {
          "rebuild": 0,
          "root_url": "https://ghcr.io/v2/homebrew/core",
          "files": {
            "arm64_ventura": {
              "cellar": "/opt/homebrew/Cellar",
              "url": "https://ghcr.io/v2/homebrew/core/ruby/blobs/sha256:0cfdc02d0fe27f2d26d6846be5a37ef98ad05e39eb6e8610faba23dc321ab31e",
              "sha256": "0cfdc02d0fe27f2d26d6846be5a37ef98ad05e39eb6e8610faba23dc321ab31e"
            },
            "arm64_monterey": {
              "cellar": "/opt/homebrew/Cellar",
              "url": "https://ghcr.io/v2/homebrew/core/ruby/blobs/sha256:31217c5ddf91622cb444b41e3fa27e91e09606a45732b84e8f680b4020c2fe6e",
              "sha256": "31217c5ddf91622cb444b41e3fa27e91e09606a45732b84e8f680b4020c2fe6e"
            },
            "arm64_big_sur": {
              "cellar": "/opt/homebrew/Cellar",
              "url": "https://ghcr.io/v2/homebrew/core/ruby/blobs/sha256:1bf22db112a85a2c3d39d8f36c2794a1023a072eb6743bd72cc7db5edc5cc46e",
              "sha256": "1bf22db112a85a2c3d39d8f36c2794a1023a072eb6743bd72cc7db5edc5cc46e"
            },
            "monterey": {
              "cellar": "/usr/local/Cellar",
              "url": "https://ghcr.io/v2/homebrew/core/ruby/blobs/sha256:519a9dca4f576cb54858ca6b8371891d4bbfa7268e3baf2839996eac0a253b10",
              "sha256": "519a9dca4f576cb54858ca6b8371891d4bbfa7268e3baf2839996eac0a253b10"
            },
            "big_sur": {
              "cellar": "/usr/local/Cellar",
              "url": "https://ghcr.io/v2/homebrew/core/ruby/blobs/sha256:49cbb1dddd7c8c7449b7df170c7ee704d36ae4aafdf985eb12d8eccaf91bea76",
              "sha256": "49cbb1dddd7c8c7449b7df170c7ee704d36ae4aafdf985eb12d8eccaf91bea76"
            },
            "catalina": {
              "cellar": "/usr/local/Cellar",
              "url": "https://ghcr.io/v2/homebrew/core/ruby/blobs/sha256:e0ab84261c665f24bcd88a8ff6b9cecd7fedb92636da43518d128f4f048a7627",
              "sha256": "e0ab84261c665f24bcd88a8ff6b9cecd7fedb92636da43518d128f4f048a7627"
            },
            "x86_64_linux": {
              "cellar": "/home/linuxbrew/.linuxbrew/Cellar",
              "url": "https://ghcr.io/v2/homebrew/core/ruby/blobs/sha256:4382b9a0940dbfbf8e3b8b63b1e2602e1fa0cabdd6acc7be83ef66077c7d6adc",
              "sha256": "4382b9a0940dbfbf8e3b8b63b1e2602e1fa0cabdd6acc7be83ef66077c7d6adc"
            }
          }
        }
      },
      "keg_only": true,
      "keg_only_reason": {
        "reason": ":provided_by_macos",
        "explanation": ""
      },
      "options": [

      ],
      "build_dependencies": [
        "pkg-config"
      ],
      "dependencies": [
        "libyaml",
        "openssl@1.1",
        "readline"
      ],
      "test_dependencies": [

      ],
      "recommended_dependencies": [

      ],
      "optional_dependencies": [

      ],
      "uses_from_macos": [
        "libffi",
        "libxcrypt",
        "zlib"
      ],
      "requirements": [

      ],
      "conflicts_with": [

      ],
      "caveats": "By default, binaries installed by gem will be placed into:\n  $(brew --prefix)/lib/ruby/gems/3.1.0/bin\n\nYou may want to add this to your PATH.\n",
      "installed": [
        {
          "version": "3.1.2_1",
          "used_options": [

          ],
          "built_as_bottle": false,
          "poured_from_bottle": false,
          "time": 1667913286,
          "runtime_dependencies": [
            {
              "full_name": "libyaml",
              "version": "0.2.5",
              "declared_directly": true
            },
            {
              "full_name": "ca-certificates",
              "version": "2022-10-11",
              "declared_directly": false
            },
            {
              "full_name": "openssl@1.1",
              "version": "1.1.1s",
              "declared_directly": true
            },
            {
              "full_name": "readline",
              "version": "8.2.1",
              "declared_directly": true
            }
          ],
          "installed_as_dependency": false,
          "installed_on_request": true
        }
      ],
      "linked_keg": null,
      "pinned": false,
      "outdated": false,
      "deprecated": false,
      "deprecation_date": null,
      "deprecation_reason": null,
      "disabled": false,
      "disable_date": null,
      "disable_reason": null
    }
  ],
  "casks": [

  ]
}

The latest stable version is being shown as 3.1.2 but installed version as 3.1.2_1.
Is this a bug, or expected?
Are these values not the correct way to be checking in integrated tooling whether a package is outdated?

Thank you

[SMillerDev]

brew outdated [--json] is the best way to check if anything is outdated locally. You're currently comparing the upstream version with the package version which doesn't always match.