Fix sqlc fmt corruption in PostgreSQL and MySQL formatters (#4596)

Fix six root causes of corruption found by running sqlc fmt across the
endtoend test corpus and verifying the results:

PostgreSQL: a named parameter with a cast (@name::type) printed as
'@ name::type' because the cast binds tighter than the @ operator, so the
printer saw a prefix operator and added a space — silently dropping the
parameter from generated code. Prefix sigils now glue to operands that
start with an identifier.

MySQL (dolphin): the formatter reprinted from the compiler's normalized
AST, which loses information the compiler doesn't need but a formatter
must keep. sqlc fmt now uses a format parser that preserves identifier
case (table names are case-sensitive on most servers), and the converter
keeps what it used to drop:

- NULL, TRUE/FALSE, and decimal literals convert by datum kind, so
  NULL no longer prints as '', 1.0 as 0, or true as 1. This also fixes
  type inference: a bool literal column is now bool, not int32
  (selectstatic golden regenerated).
- SELECT DISTINCT keeps its DISTINCT.
- The ORDER BY of a compound (UNION) statement survives.
- GROUP_CONCAT(... ORDER BY ...) keeps its ordering.
- Optimizer hints (/*+ ... */) are carried through to printing.
- Multi-table UPDATE keeps its JOIN's ON condition and the table
  qualifiers in SET.
- DECIMAL(p,s) precision and UNSIGNED survive in column definitions.

Backstop: dolphin now implements Fingerprint (via marino's restore with
identifier case preserved and redundant parens unwrapped), giving MySQL
the same proof PostgreSQL has: fmt accepts a formatted statement only
when it provably means what the author wrote, and otherwise leaves the
statement exactly as written. That is what fixes SHOW WARNINGS, which
the parser rewrites into a synthetic SELECT for analysis: it now falls
back to the original text instead of printing the internal form.


Claude-Session: https://claude.ai/code/session_01UZBvADuHMZEjoF551NccgP

Co-authored-by: Claude <noreply@anthropic.com>

Author: kyleconroy

internal/cmd/fmt.go

@@ -49,7 +49,9 @@ func newQueryFormatter(engine config.Engine) queryFormatter {
 	case config.EngineSQLite:
 		return sqlite.NewParser()
 	case config.EngineMySQL:
-		return dolphin.NewParser()
+		// The format parser preserves identifier case and proves every
+		// statement via Fingerprint, the way oliphant does for PostgreSQL.
+		return dolphin.NewFormatParser()
 	default:
 		return nil
 	}

internal/endtoend/testdata/fmt/mysql/query.sql

@@ -39,3 +39,34 @@ insert into authors (
 ) values (
   ?, ?
 );
+
+-- name: CasePreserved :many
+SELECT ID, Name FROM Authors WHERE Name <> '' ORDER BY Name;
+
+-- name: LiteralsSurvive :one
+SELECT true AS t, false AS f, 1.50 AS score, CASE WHEN name = '' THEN NULL ELSE name END AS n FROM authors LIMIT 1;
+
+-- name: DistinctNames :many
+SELECT DISTINCT name FROM authors;
+
+-- name: UnionOrdered :many
+SELECT name AS foo FROM authors
+UNION
+SELECT bio AS foo FROM authors
+ORDER BY foo;
+
+-- name: ConcatNames :many
+SELECT group_concat(DISTINCT name ORDER BY name DESC SEPARATOR ' ') FROM authors GROUP BY bio;
+
+-- name: Hinted :one
+SELECT /*+ MAX_EXECUTION_TIME(1000) */ id FROM authors LIMIT 1;
+
+-- name: UpdateWithJoin :exec
+UPDATE authors AS a JOIN authors AS p ON p.id = a.id
+SET a.name = ?
+WHERE p.bio IS NOT NULL;
+
+-- name: ShowWarnings :many
+SHOW WARNINGS;
+
+CREATE TABLE scores (points decimal(10, 5), views bigint unsigned NOT NULL);

internal/endtoend/testdata/fmt/mysql/stdout.txt

@@ -43,7 +43,7 @@
 
  -- name: CastUnsigned :one
  SELECT CAST(id AS UNSIGNED) FROM authors LIMIT 1;
-@@ -34,8 +39,5 @@
+@@ -34,14 +39,11 @@
  SELECT id FROM authors LIMIT 1;
 
  -- name: CreateAuthor :execresult
@@ -54,3 +54,20 @@
 -) values (
 -  ?, ?
 -);
+ 
+ -- name: CasePreserved :many
++SELECT ID, Name FROM Authors WHERE Name != '' ORDER BY Name;
+-SELECT ID, Name FROM Authors WHERE Name <> '' ORDER BY Name;
+ 
+ -- name: LiteralsSurvive :one
+ SELECT true AS t, false AS f, 1.50 AS score, CASE WHEN name = '' THEN NULL ELSE name END AS n FROM authors LIMIT 1;
+@@ -62,7 +64,8 @@
+ SELECT /*+ MAX_EXECUTION_TIME(1000) */ id FROM authors LIMIT 1;
+ 
+ -- name: UpdateWithJoin :exec
++UPDATE authors AS a
++JOIN authors AS p ON p.id = a.id
+-UPDATE authors AS a JOIN authors AS p ON p.id = a.id
+ SET a.name = ?
+ WHERE p.bio IS NOT NULL;
+ 

internal/endtoend/testdata/fmt/postgresql/query.sql

@@ -26,5 +26,8 @@ WHERE id > $1;
 -- name: SearchAuthors :many
 SELECT id, name, bio, created_at FROM authors WHERE name LIKE $1 AND bio IS NOT NULL AND id > $2 AND name <> $3 ORDER BY name, id LIMIT $4;
 
+-- name: AtParamsGlued :many
+SELECT name FROM authors WHERE name = @slug AND @filter::bool;
+
 -- name: DeleteAuthor :exec
-DELETE FROM authors WHERE id = @id
+DELETE FROM authors WHERE id = @id

internal/endtoend/testdata/fmt/postgresql/stdout.txt

@@ -40,8 +40,8 @@
  FROM authors
  WHERE id > $1;
 
-@@ -27,4 +27,4 @@
- SELECT id, name, bio, created_at FROM authors WHERE name LIKE $1 AND bio IS NOT NULL AND id > $2 AND name <> $3 ORDER BY name, id LIMIT $4;
+@@ -30,4 +30,4 @@
+ SELECT name FROM authors WHERE name = @slug AND @filter::bool;
 
  -- name: DeleteAuthor :exec
 -DELETE FROM authors WHERE id = @id