{
  "$type": "site.standard.document",
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  "path": "/t/pre-rfc-dns-domains-as-package-namespaces/24202?page=3#post_48",
  "publishedAt": "2026-04-30T06:33:07.000Z",
  "site": "https://internals.rust-lang.org",
  "tags": [
    "crates.io"
  ],
  "textContent": "I thought of another way to explain it, by analogy with `lib.name`.\n\nIf you have a package at `https://crates,io/crates/some-example-lib`, the name that will be exposed to `rustc` is expected to be `some_example_lib`. The transformation from crates.io package name to `rustc` library name is simple to understand and can be implemented mechanically.\n\nThe `lib.name` field can be overridden with an ~arbitrary value, for example I could use it so that the `https://crates,io/crates/some-example-lib` package was exposed to `rustc` as `completely_different_name`. This severs the connection between the package named and the library name -- it's no longer possible to predict what the library would be called.\n\nIf I were to publish a package `https://crates,io/crates/jmillikin-serde-json` then the only obvious choice for the name that's exposed to `rustc` is `jmillikin_serde_json`. If I were to set `lib.name` to `serde_json` then that would be confusing -- it's different from what users expect, and there's no way to predict it. There's no mechanical transformation that can be applied to the string `\"jmillikin-serde-json\"` to produce `\"serde_json\"` without generating incorrect results for similar names.\n\nThe reason to have a delimiter like `jmillikin/json` or `(jmillikin)json` is so that the mechanical transformation of a package name to a library name remains possible.\n\nConcerns about the possibility of changing usernames have caused `jmillikin-json` to be a valid package name but `jmillikin/json` to be an invalid package name -- the latter uses a namespace syntax, and namespaces can't be usernames, because usernames are mutable.\n\nFrom the perspective of the crates.io database the strings `\"john-millikin.com/json\"` and `\"john-millikin-com-json\"` aren't materially different, but to everything downstream of crates.io the difference is important because the former can be parsed to extract the library name and the latter can't.\n\nIf you're OK with a package being published with the name `\"john-millikin-com-json\"` and `lib.name = \"json\"`, then why would you not want to allow the semantically equivalent and much easier to work with `\"john-millikin.com/json\"` package name?",
  "title": "[Pre-RFC] DNS domains as package namespaces"
}