flycheck-parse-cargo-rustc

flycheck.el

(defun flycheck-parse-cargo-rustc (output checker buffer)
  "Parse Cargo errors from OUTPUT and return a list of `flycheck-error'.

CHECKER and BUFFER denote the CHECKER that returned OUTPUT and
the BUFFER that was checked respectively.

The expected format for OUTPUT is a mix of plain text lines and
JSON lines.  This function ignores the plain text lines and
parses only JSON lines.  Each JSON line is expected to be a JSON
object that represents a message from Cargo.  The format of
messages emitted by Cargo is described in cargo's
machine_message.rs at URL `https://git.io/vh24R'."
  (let ((errors))
    (dolist (msg (flycheck-parse-json output))
      (let-alist msg
        ;; Errors and warnings from rustc are wrapped by cargo, so we filter and
        ;; unwrap them, and delegate the actual construction of `flycheck-error'
        ;; objects to `flycheck-parse-rustc-diagnostic'.
        ;; Check whether the code is non-nil because Rust≥1.44 includes the
        ;; warning count upon completion.
        (when (and (string= .reason "compiler-message")
                   (or .message.code
                       (string-prefix-p "error: expected one of" .message.rendered)))
          (push (flycheck-parse-rustc-diagnostic .message checker buffer)
                errors))))
    (apply #'nconc errors)))