Can we fix a build unit at a time, rather than package

[epage]

#15 had us switch to fixing a package at a time but build units can also depend on each other (bin, examples, and tests depending on a lib) and we should resolve the lib before resolving the other build units that depend on it.

[epage]

Looking at a build, I think the answer is "yes"

$ cargo clean && RUSTFLAGS=-Wpedantic cargo clippy --example dump-style --message-format json
     Removed 29 files, 3.6MiB total
    Checking lexopt v0.3.0
    Checking anstyle v1.0.11 (/home/epage/src/personal/anstyle/crates/anstyle)
{"reason":"compiler-message","package_id":"path+file:///home/epage/src/personal/anstyle/crates/anstyle#1.0.11","manife
st_path":"/home/epage/src/personal/anstyle/crates/anstyle/Cargo.toml","target":{"kind":["lib"],"crate_types":["lib"],"
name":"anstyle","src_path":"/home/epage/src/personal/anstyle/crates/anstyle/src/lib.rs","edition":"2021","doc":true,"d
octest":true,"test":true},"message":{"rendered":"warning: lint name `pedantic` is deprecated and may not have an effec
t in the future\n  |\n  = help: change it to clippy::pedantic\n  = note: requested on the command line with `-W pedant
ic`\n  = note: `#[warn(renamed_and_removed_lints)]` on by default\n\n","$message_type":"diagnostic","children":[{"chil
dren":[],"code":null,"level":"help","message":"change it to clippy::pedantic","rendered":null,"spans":[]},{"children":
[],"code":null,"level":"note","message":"requested on the command line with `-W pedantic`","rendered":null,"spans":[]}
,{"children":[],"code":null,"level":"note","message":"`#[warn(renamed_and_removed_lints)]` on by default","rendered":n
ull,"spans":[]}],"code":{"code":"renamed_and_removed_lints","explanation":null},"level":"warning","message":"lint name
 `pedantic` is deprecated and may not have an effect in the future","spans":[]}}
{"reason":"compiler-artifact","package_id":"registry+https://github.com/rust-lang/crates.io-index#lexopt@0.3.0","manif
est_path":"/home/epage/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/lexopt-0.3.0/Cargo.toml","target":{"kind":
["lib"],"crate_types":["lib"],"name":"lexopt","src_path":"/home/epage/.cargo/registry/src/index.crates.io-1949cf8c6b5b
557f/lexopt-0.3.0/src/lib.rs","edition":"2018","doc":true,"doctest":true,"test":true},"profile":{"opt_level":"0","debu
ginfo":2,"debug_assertions":true,"overflow_checks":true,"test":false},"features":[],"filenames":["/home/epage/src/pers
onal/anstyle/target/debug/deps/liblexopt-33c87633f0e7d5db.rmeta"],"executable":null,"fresh":false}
{"reason":"compiler-artifact","package_id":"path+file:///home/epage/src/personal/anstyle/crates/anstyle#1.0.11","manif
est_path":"/home/epage/src/personal/anstyle/crates/anstyle/Cargo.toml","target":{"kind":["lib"],"crate_types":["lib"],
"name":"anstyle","src_path":"/home/epage/src/personal/anstyle/crates/anstyle/src/lib.rs","edition":"2021","doc":true,"
doctest":true,"test":true},"profile":{"opt_level":"0","debuginfo":2,"debug_assertions":true,"overflow_checks":true,"te
st":false},"features":["default","std"],"filenames":["/home/epage/src/personal/anstyle/target/debug/deps/libanstyle-9a
a42ead31979327.rmeta"],"executable":null,"fresh":false}
{"reason":"compiler-message","package_id":"path+file:///home/epage/src/personal/anstyle/crates/anstyle#1.0.11","manife
st_path":"/home/epage/src/personal/anstyle/crates/anstyle/Cargo.toml","target":{"kind":["example"],"crate_types":["bin
"],"name":"dump-style","src_path":"/home/epage/src/personal/anstyle/crates/anstyle/examples/dump-style.rs","edition":"
2021","doc":false,"doctest":false,"test":false},"message":{"rendered":"warning: lint name `pedantic` is deprecated and
 may not have an effect in the future\n  |\n  = help: change it to clippy::pedantic\n  = note: requested on the comman
d line with `-W pedantic`\n  = note: `#[warn(renamed_and_removed_lints)]` on by default\n\n","$message_type":"diagnost
ic","children":[{"children":[],"code":null,"level":"help","message":"change it to clippy::pedantic","rendered":null,"s
pans":[]},{"children":[],"code":null,"level":"note","message":"requested on the command line with `-W pedantic`","rend
ered":null,"spans":[]},{"children":[],"code":null,"level":"note","message":"`#[warn(renamed_and_removed_lints)]` on by
 default","rendered":null,"spans":[]}],"code":{"code":"renamed_and_removed_lints","explanation":null},"level":"warning
","message":"lint name `pedantic` is deprecated and may not have an effect in the future","spans":[]}}
{"reason":"compiler-artifact","package_id":"path+file:///home/epage/src/personal/anstyle/crates/anstyle#1.0.11","manif
est_path":"/home/epage/src/personal/anstyle/crates/anstyle/Cargo.toml","target":{"kind":["example"],"crate_types":["bi
n"],"name":"dump-style","src_path":"/home/epage/src/personal/anstyle/crates/anstyle/examples/dump-style.rs","edition":
"2021","doc":false,"doctest":false,"test":false},"profile":{"opt_level":"0","debuginfo":2,"debug_assertions":true,"ove
rflow_checks":true,"test":false},"features":["default","std"],"filenames":["/home/epage/src/personal/anstyle/target/de
bug/examples/libdump_style-106d7d69248b6287.rmeta"],"executable":null,"fresh":false}
{"reason":"build-finished","success":true}
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.22s

Looking at the message

{
  "reason": "compiler-message",
  "package_id": "path+file:///home/epage/src/personal/anstyle/crates/anstyle#1.0.11",
  "manifest_path": "/home/epage/src/personal/anstyle/crates/anstyle/Cargo.toml",
  "target": {
    "kind": [
      "lib"
    ],
    "crate_types": [
      "lib"
    ],
    "name": "anstyle",
    "src_path": "/home/epage/src/personal/anstyle/crates/anstyle/src/lib.rs",
    "edition": "2021",
    "doc": true,
    "doctest": true,
    "test": true
  },
  "message": {
    "rendered": "warning: lint name `pedantic` is deprecated and may not have an effect in the future\n  |\n  = help: change it to clippy::pedantic\n  = note: requested on the command line with `-W pedantic`\n  = note: `#[warn(renamed_and_removed_lints)]` on by default\n\n",
    "$message_type": "diagnostic",
    "children": [
      {
        "children": [],
        "code": null,
        "level": "help",
        "message": "change it to clippy::pedantic",
        "rendered": null,
        "spans": []
      },
      {
        "children": [],
        "code": null,
        "level": "note",
        "message": "requested on the command line with `-W pedantic`",
        "rendered": null,
        "spans": []
      },
      {
        "children": [],
        "code": null,
        "level": "note",
        "message": "`#[warn(renamed_and_removed_lints)]` on by default",
        "rendered": null,
        "spans": []
      }
    ],
    "code": {
      "code": "renamed_and_removed_lints",
      "explanation": null
    },
    "level": "warning",
    "message": "lint name `pedantic` is deprecated and may not have an effect in the future",
    "spans": []
  }
}

The target section seems to have enough information to unique identify a build target

[Pyr0de]

Should we solve this the same way as #15, by filtering the messages and collecting only the necessary ones?

Can we filter the messages using target.crate_type from the json?

Would it be safe to assume that errors for *lib crate_types will always come before bin? If that is the case, for a package, we could collect all the errors up till bin and work on those, right?

[epage]

Should we solve this the same way as #15, by filtering the messages and collecting only the necessary ones?

I believe so

Can we filter the messages using target.crate_type from the json?

crate_types are

pub enum CrateType {
    Bin,
    Lib,
    Rlib,
    Dylib,
    Cdylib,
    Staticlib,
    ProcMacro,
    Other(String),
}

That might be able to work though I'd recommend being conservative and just hash nearly all of the target field.

Would it be safe to assume that errors for *lib crate_types will always come before bin? If that is the case, for a package, we could collect all the errors up till bin and work on those, right?

This would likely rely too much on implementation details and be brittle. Let's keep things simple in this pass but then track this as a potential further optimization.

A Bin comes before a Lib when its a build script.

rust-lang/rfcs#3826 would have a ProcMacro come before a Lib.

[Pyr0de]

This would likely rely too much on implementation details and be brittle. Let's keep things simple in this pass but then track this as a potential further optimization.

How should I implement this?

[epage]

Augment our seen and current by also tracking what build target we are on and keep the rest of the logic the same.