Shorten Dep serialization format in common cases

[lihaoyi]

Fixes #3417

We do a best-effort approach where we try to reverse the Dep.parse logic, and at the end do a == check to see if the round tripped Dep is identical to the original. There's some overhead with the round trip comparison - effectively for each write-read of a Dep we add an additional read - but this isn't a hot code path so it shouldn't be a big deal. In exchange we get a pretty good guarantee of correctness that later on when someone round-trips the same Dep off of disk, they get the same result. We do the same for BoundDep and re-use most of the Dep logic

The sophistication of our def parse and def unparse logic can be extended over time, but this should work well for 99% of dependencies which are simple without fancy exclusions, publication, configuration, optional, transitive, etc.

Added some assertions to ResolveDepsTests to check the round tripping for common scenarios, both simplified and not

Before:

lihaoyi mill$ ./mill show main.api.ivyDeps
[
  {
    "dep": {
      "module": {
        "organization": {
          "value": "com.lihaoyi"
        },
        "name": {
          "value": "os-lib"
        },
        "attributes": {}
      },
      "version": "0.10.7-M1",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "cross": {
      "$type": "mill.scalalib.CrossVersion.Binary",
      "platformed": false
    },
    "force": false
  },
  {
    "dep": {
      "module": {
        "organization": {
          "value": "com.lihaoyi"
        },
        "name": {
          "value": "upickle"
        },
        "attributes": {}
      },
      "version": "3.3.1",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "cross": {
      "$type": "mill.scalalib.CrossVersion.Binary",
      "platformed": false
    },
    "force": false
  },
  {
    "dep": {
      "module": {
        "organization": {
          "value": "com.lihaoyi"
        },
        "name": {
          "value": "pprint"
        },
        "attributes": {}
      },
      "version": "0.9.0",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "cross": {
      "$type": "mill.scalalib.CrossVersion.Binary",
      "platformed": false
    },
    "force": false
  },
  {
    "dep": {
      "module": {
        "organization": {
          "value": "com.lihaoyi"
        },
        "name": {
          "value": "fansi"
        },
        "attributes": {}
      },
      "version": "0.5.0",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "cross": {
      "$type": "mill.scalalib.CrossVersion.Binary",
      "platformed": false
    },
    "force": false
  },
  {
    "dep": {
      "module": {
        "organization": {
          "value": "org.scala-sbt"
        },
        "name": {
          "value": "test-interface"
        },
        "attributes": {}
      },
      "version": "1.0",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "cross": {
      "$type": "mill.scalalib.CrossVersion.Constant",
      "value": "",
      "platformed": false
    },
    "force": false
  }
]
lihaoyi mill$ ./mill show main.api.transitiveIvyDeps
[
  {
    "dep": {
      "module": {
        "organization": {
          "value": "com.lihaoyi"
        },
        "name": {
          "value": "os-lib_2.13"
        },
        "attributes": {}
      },
      "version": "0.10.7-M1",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "force": false
  },
  {
    "dep": {
      "module": {
        "organization": {
          "value": "com.lihaoyi"
        },
        "name": {
          "value": "upickle_2.13"
        },
        "attributes": {}
      },
      "version": "3.3.1",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "force": false
  },
  {
    "dep": {
      "module": {
        "organization": {
          "value": "com.lihaoyi"
        },
        "name": {
          "value": "pprint_2.13"
        },
        "attributes": {}
      },
      "version": "0.9.0",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "force": false
  },
  {
    "dep": {
      "module": {
        "organization": {
          "value": "com.lihaoyi"
        },
        "name": {
          "value": "fansi_2.13"
        },
        "attributes": {}
      },
      "version": "0.5.0",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "force": false
  },
  {
    "dep": {
      "module": {
        "organization": {
          "value": "org.scala-sbt"
        },
        "name": {
          "value": "test-interface"
        },
        "attributes": {}
      },
      "version": "1.0",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "force": false
  },
  {
    "dep": {
      "module": {
        "organization": {
          "value": "org.scala-lang"
        },
        "name": {
          "value": "scala-library"
        },
        "attributes": {}
      },
      "version": "2.13.14",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "force": true
  },
  {
    "dep": {
      "module": {
        "organization": {
          "value": "com.lihaoyi"
        },
        "name": {
          "value": "mill-moduledefs_2.13"
        },
        "attributes": {}
      },
      "version": "0.11.0-M2",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "force": false
  },
  {
    "dep": {
      "module": {
        "organization": {
          "value": "com.kohlschutter.junixsocket"
        },
        "name": {
          "value": "junixsocket-core"
        },
        "attributes": {}
      },
      "version": "2.10.0",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "force": false
  }
]

After:

lihaoyi mill$ ./mill show main.api.ivyDeps
[
  "com.lihaoyi::os-lib:0.10.7-M1",
  "com.lihaoyi::upickle:3.3.1",
  "com.lihaoyi::pprint:0.9.0",
  "com.lihaoyi::fansi:0.5.0",
  "org.scala-sbt:test-interface:1.0"
]

lihaoyi mill$ ./mill show main.api.transitiveIvyDeps
[
  "com.lihaoyi:os-lib_2.13:0.10.7-M1",
  "com.lihaoyi:upickle_2.13:3.3.1",
  "com.lihaoyi:pprint_2.13:0.9.0",
  "com.lihaoyi:fansi_2.13:0.5.0",
  "org.scala-sbt:test-interface:1.0",
  {
    "dep": {
      "module": {
        "organization": {
          "value": "org.scala-lang"
        },
        "name": {
          "value": "scala-library"
        },
        "attributes": {}
      },
      "version": "2.13.14",
      "configuration": {
        "value": "default(compile)"
      },
      "minimizedExclusions": {
        "data": "coursier.core.MinimizedExclusions.ExcludeNone"
      },
      "publication": {
        "name": "",
        "type": {
          "value": ""
        },
        "ext": {
          "value": ""
        },
        "classifier": {
          "value": ""
        }
      },
      "optional": false,
      "transitive": true
    },
    "force": true
  },
  "com.lihaoyi:mill-moduledefs_2.13:0.11.0-M2",
  "com.kohlschutter.junixsocket:junixsocket-core:2.10.0"
]

Note that org.scala-lang:scala-library is still using the old verbose serialization, due to .forceVersion() which makes it unable to be parsed/unparsed into a naked string literal as it needs a .forceVersion() call. We could make the shorthand serialization smarter to deal with this in future, but for now this is already a huge improvement over the status quo

[lihaoyi]

Part of the reason that the coursier.Dependency serialization is so verbose is that Coursier does not use Scala language default parameter values for its optional parameters, and instead uses Java-style telescoping to preserve binary compatibility.

This works fine in Scala code, but as uPickle relies on Scala default parameter values to elide unnecessary fields, it is unable to recognize the telescoping apply methods as default values, and thus fully serializes everything including the default values.

If Coursier data types provided default values to apply, the serialization of scala-library above would be a lot shorter:

 {
    "dep": {
      "module": {
        "organization": {
          "value": "org.scala-lang"
        },
        "name": {
          "value": "scala-library"
        }
      },
      "version": "2.13.14"
    },
    "force": true
  },