pub trait moved, deleted, or renamed

[obi1kenobi]

No description provided.

[seanchen1991]

Hi, I'm interested in taking on this issue.

As per this point in CONTRIBUTING.md:

try to identify a related lint that is already implemented and relies on similar information

What's the most closely-related lint that I could reference for this? Also, is there any documentation on the query syntax?

[obi1kenobi]

Great choice! There are several very related lints:

• struct moved, deleted, or renamed: https://github.com/obi1kenobi/cargo-semver-check/blob/main/src/queries/struct_missing.ron
• enum moved, deleted, or renamed: https://github.com/obi1kenobi/cargo-semver-check/blob/main/src/queries/enum_missing.ron
• function moved, deleted, or renamed: https://github.com/obi1kenobi/cargo-semver-check/blob/main/src/queries/function_missing.ron

There are some resources for using the query language, but I'd recommend using them as a reference rather than as a "getting started" guide: look up what you need when you need it, rather than reading them end-to-end first.

• The query language is from the Trustfall project. The docs are sadly still lacking, but I'll walk you through the functionality used here.
• The syntax is also very related (very minor tweaks) to my prior GraphQL compiler project which has a fairly extensive reference. The biggest differences are that the filter and output directives' arguments in Trustfall have shorter, more convenient names (op_name -> op, out_name -> name).

As a first step, I'd recommend trying to write just the new query; we can add the error message text, test case, etc. afterward. I'd recommend copy-pasting the query text out of those files and into files where you can enable GraphQL syntax highlighting:

Look for similarities between the queries. You'll notice that they are nearly identical, with minute differences. They all say the following:

• Given a CrateDiff comparison across crate versions, look in the baseline version for items that are specifically <enum/struct/fn>, which are public ($public is a query argument, defined in the file to have value "public"), and select some of their properties for output (@output) and for later filtering (@tag).
• Then, look in the current version for a matching item (enum/struct/fn), also public, whose name matches the earlier one (%name refers to name @tag from before), and which is importable via the same path as in the baseline (again, %path refers to path @tag from earlier).
• The current @fold @transform(op: "count") @filter(op: "=", value: ["$zero"]) part means "aggregate all such matching current data into a list, then ensure its element count is zero -- an empty list. When we don't find any matching current items, that item must have been moved, deleted, or renamed, which is what we are looking for.
• span @optional means "include span information if available, but leave it None otherwise rather than discarding from the search all items lacking span information.

This is very similar to what we'll need for traits as well: traits are items too, just like enums and structs and functions. The queryable schema is here if you'd like to check which properties, edges, or types exist: https://github.com/obi1kenobi/cargo-semver-check/blob/main/src/rustdoc_schema.graphql

Ping me with any questions! Happy to hop on a video call if that would make it easier to get started, and I'm also in the rust-lang zulip if you'd prefer more interactive text chat.

I'm also working with a few friends on a WASM-powered web editor for Trustfall queries with all the modern conveniences (autocomplete, syntax highlighting, etc.), stay tuned! 🤞