Remove HINT mode.

What is the purpose of metadata hints in Clojure?

I don't know if I should add this to the CHANGES.md

Please, the more detail the better though if you did a "lots of fixes" with a second level bullet list under that that would be even better.

What is the purpose of metadata hints in Clojure?

General meta information. Anything really.

The test function in clojure.core executes the :test meta key.

(defn my-function
  "this function adds two numbers"
  {:test #(do
            (assert (= (my-function 2 3) 5))
            (assert (= (my-function 4 4) 8)))}
  ([x y] (+ x y)))
  
(meta #'my-function)
; => {:arglists ([x y]), 
;     :doc "this function adds two numbers", 
;     :test #object[user$fn__143 0x4482469c "user$fn__143@4482469c"], 
;     :line 1, :column 1, :file "NO_SOURCE_PATH", 
;     :name my-function, 
;     :ns #object[clojure.lang.Namespace 0x3703bf3c "user"]}

(test #'my-function)
; => :ok

clojure.core uses it for documentation and compiler hints.

CIDER the Clojure Emacs IDE uses it for breakpoints.

(dotimes [i 10]
  #dbg ^{:break/when (= i 7)}
  (prn i))

koacha, a test runner, uses them to focus on specific sets of tests

(deftest ^:yyy other-test
  (is (= 3 3)))

meta-merge uses keys in metadata to specify per-key merge behaviour.

(meta-merge {:a [:b :c]} {:a ^:prepend [:d]})
; => {:a [:d :b :c]}
(meta-merge {:a [:b :c]} {:a ^:replace [:d]})
; => {:a [:d]}
(meta-merge {:a [:b :c]} {:a ^:displace [:d]})
; => {:a [:b :c]}

https://clojure.org/reference/reader#_metadata

Metadata (^)

Metadata is a map associated with some kinds of objects: Symbols, Lists, Vector, Sets, Maps, tagged literals returning an IMeta, and record, type, and constructor calls. The metadata reader macro first reads the metadata and attaches it to the next form read (see with-meta to attach meta to an object):
^{:a 1 :b 2} [1 2 3] yields the vector [1 2 3] with a metadata map of {:a 1 :b 2}.

A shorthand version allows the metadata to be a simple symbol or string, in which case it is treated as a single entry map with a key of :tag and a value of the (resolved) symbol or string, e.g.:
^String x is the same as ^{:tag java.lang.String} x

Such tags can be used to convey type information to the compiler.

Another shorthand version allows the metadata to be a keyword, in which case it is treated as a single entry map with a key of the keyword and a value of true, e.g.:
^:dynamic x is the same as ^{:dynamic true} x

Metadata can be chained in which case they are merged from right to left.

highlight.js does not have regex languages, does it?

Maybe an idea for the future, as GitHub supports regex highlighting.

#"\bMy\sRegex!\b"   ; Special regex stuff is highlighted
"\bMy\sRegex!\b"  

But not in all languages 🤔

const RE = /\bMy\sRegex!\b/;

Special regex stuff is highlighted

See the history behind #2751. I'm open to this, but we do not need (or want) a whole regex grammar. (there is sadly no good way to reuse it properly at the moment). If we picked a few key things to focus on and decided to do that within our existing regex support, I think that could be nice. And it would only involve changing: REGEXP_MODE and most every grammar would benefit.

One easy start would be start by moving the existing escapes we recognize into char.escape scope. If you wanted to tackle that separately...

Looking good, almost there!

@MrEbbinghaus Thanks so much for help on this!

@joshgoebel Thank you for the clear and fast review. :-)