#515: exclude some entities from smart quoting

this is a partial solution, intended to catch (and quote) things like
`0abc` while not changing the behavior for `80` or `2023_11_20`

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 * 2.5.next in progress
   * Review metadata -> SQL logic?
-  * Review quoting logic?
+  * Address [#515](https://github.com/seancorfield/honeysql/issues/515) in part by quoting entities that start with a digit but are otherwise alphanumeric. Note that entities that are all digits (optionally including underscores) will still not be quoted as in previous releases.
 
 * 2.5.1091 -- 2023-10-28
   * Address [#512](https://github.com/seancorfield/honeysql/issues/512) by adding support for subqueries in the `:array` special syntax (for BigQuery and PostgreSQL). This also adds support for metadata on the `:select` value to produce `AS STRUCT` or `DISTINCT`.

src/honey/sql.cljc

@@ -244,8 +244,12 @@
   )
 
 (def ^:private alphanumeric
-  "Basic regex for entities that do not need quoting."
-  #"^[A-Za-z0-9_]+$")
+  "Basic regex for entities that do not need quoting.
+   Either:
+   * the whole entity is numeric (with optional underscores), or
+   * the first character is alphabetic (or underscore) and the rest is
+     alphanumeric (or underscore)."
+  #"^([0-9_]+|[A-Za-z_][A-Za-z0-9_]*)$")
 
 (defn format-entity
   "Given a simple SQL entity (a keyword or symbol -- or string),