Remove go.mod replace directive that breaks 'go install ...@latest'

The replace directive pointing to the sqlc-dev/mysql fork was only
needed by TestExpandMySQL, but it broke the install path documented
at https://docs.sqlc.dev/en/latest/overview/install.html. Fixes #4397.

Rewrite MySQLColumnGetter in internal/x/expander/expander_test.go to
read column names from sql.Rows (the test tables are empty, so no rows
are transferred), then drop the replace directive from go.mod.

Add TestGoModHasNoReplaceDirectives and a dedicated CI job so the same
regression surfaces as a quick, obvious failure rather than silently
shipping in a release.

Author: claude

.github/workflows/ci.yml

@@ -22,6 +22,22 @@ jobs:
         CGO_ENABLED: "0"
         GOOS: ${{ matrix.goos }}
         GOARCH: ${{ matrix.goarch }}
+  # Runs the TestGoModHasNoReplaceDirectives test (and nothing else) as its own
+  # job so a regression of https://github.com/sqlc-dev/sqlc/issues/4397 is easy
+  # to spot in the GitHub UI. The full 'test' job below runs the same check as
+  # part of 'go test ./...', but it takes much longer to finish and a failure
+  # there is less obvious at a glance.
+  go_install:
+    name: verify 'go install ...@latest' compatibility
+    runs-on: ubuntu-24.04
+    steps:
+    - uses: actions/checkout@v6
+    - uses: actions/setup-go@v6
+      with:
+        go-version: '1.26.2'
+    - name: check go.mod has no replace directives
+      run: go test -run TestGoModHasNoReplaceDirectives -v .
+
   test:
     runs-on: ubuntu-24.04
     steps:

go.mod

@@ -59,5 +59,3 @@ require (
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20260120221211-b8f7ae30c516 // indirect
 	gopkg.in/natefinch/lumberjack.v2 v2.2.1 // indirect
 )
-
-replace github.com/go-sql-driver/mysql => github.com/sqlc-dev/mysql v0.0.0-20251129233104-d81e1cac6db2

go.sum

@@ -22,6 +22,8 @@ github.com/go-logr/logr v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
 github.com/go-logr/logr v1.4.3/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
 github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
 github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
+github.com/go-sql-driver/mysql v1.9.3 h1:U/N249h2WzJ3Ukj8SowVFjdtZKfu9vlLZxjPXV1aweo=
+github.com/go-sql-driver/mysql v1.9.3/go.mod h1:qn46aNg1333BRMNU69Lq93t8du/dwxI64Gl8i5p1WMU=
 github.com/golang/protobuf v1.5.4 h1:i7eJL8qZTpSEXOPTxNKhASYpMn+8e5Q6AdndVa1dWek=
 github.com/golang/protobuf v1.5.4/go.mod h1:lnTiLA8Wa4RWRcIUkrtSVa5nRhsEGBg48fD6rSs7xps=
 github.com/google/cel-go v0.28.0 h1:KjSWstCpz/MN5t4a8gnGJNIYUsJRpdi/r97xWDphIQc=
@@ -83,8 +85,6 @@ github.com/spf13/pflag v1.0.10 h1:4EBh2KAYBwaONj6b2Ye1GiHfwjqyROoF4RwYO+vPwFk=
 github.com/spf13/pflag v1.0.10/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/sqlc-dev/doubleclick v1.0.0 h1:2/OApfQ2eLgcfa/Fqs8WSMA6atH0G8j9hHbQIgMfAXI=
 github.com/sqlc-dev/doubleclick v1.0.0/go.mod h1:ODHRroSrk/rr5neRHlWMSRijqOak8YmNaO3VAZCNl5Y=
-github.com/sqlc-dev/mysql v0.0.0-20251129233104-d81e1cac6db2 h1:kmCAKKtOgK6EXXQX9oPdEASIhgor7TCpWxD8NtcqVcU=
-github.com/sqlc-dev/mysql v0.0.0-20251129233104-d81e1cac6db2/go.mod h1:TrDMWzjNTKvJeK2GC8uspG+PWyPLiY9QKvwdWpAdlZE=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=

gomod_test.go

@@ -0,0 +1,66 @@
+package sqlc
+
+import (
+	"fmt"
+	"os"
+	"strings"
+	"testing"
+)
+
+// TestGoModHasNoReplaceDirectives guards against regressions of
+// https://github.com/sqlc-dev/sqlc/issues/4397.
+//
+// When go.mod contains a replace directive, the Go toolchain refuses to run
+// `go install github.com/sqlc-dev/sqlc/cmd/sqlc@latest` (and the equivalent
+// `go run ...@latest`):
+//
+//	go: github.com/sqlc-dev/sqlc/cmd/sqlc@latest (in github.com/sqlc-dev/sqlc@v...):
+//	    The go.mod file for the module providing named packages contains one or
+//	    more replace directives. It must not contain directives that would cause
+//	    it to be interpreted differently than if it were the main module.
+//
+// https://docs.sqlc.dev/en/latest/overview/install.html tells users to run
+// exactly that command, so any replace directive slipping into go.mod breaks
+// the advertised installation path for the next release.
+func TestGoModHasNoReplaceDirectives(t *testing.T) {
+	data, err := os.ReadFile("go.mod")
+	if err != nil {
+		t.Fatalf("read go.mod: %v", err)
+	}
+
+	var (
+		inBlock   bool
+		offenders []string
+	)
+	for i, raw := range strings.Split(string(data), "\n") {
+		line := strings.TrimSpace(raw)
+		if idx := strings.Index(line, "//"); idx >= 0 {
+			line = strings.TrimSpace(line[:idx])
+		}
+
+		if inBlock {
+			if line == ")" {
+				inBlock = false
+				continue
+			}
+			if line != "" {
+				offenders = append(offenders, fmt.Sprintf("  go.mod:%d: %s", i+1, raw))
+			}
+			continue
+		}
+
+		switch {
+		case line == "replace (":
+			inBlock = true
+		case strings.HasPrefix(line, "replace "):
+			offenders = append(offenders, fmt.Sprintf("  go.mod:%d: %s", i+1, raw))
+		}
+	}
+
+	if len(offenders) > 0 {
+		t.Fatalf("go.mod must not contain replace directives; "+
+			"they break `go install github.com/sqlc-dev/sqlc/cmd/sqlc@latest`.\n"+
+			"See https://github.com/sqlc-dev/sqlc/issues/4397\n%s",
+			strings.Join(offenders, "\n"))
+	}
+}

internal/x/expander/expander_test.go

@@ -3,12 +3,10 @@ package expander
 import (
 	"context"
 	"database/sql"
-	"database/sql/driver"
-	"fmt"
 	"os"
 	"testing"
 
-	"github.com/go-sql-driver/mysql"
+	_ "github.com/go-sql-driver/mysql"
 	"github.com/jackc/pgx/v5/pgxpool"
 	"github.com/ncruces/go-sqlite3"
 
@@ -44,46 +42,28 @@ func (g *PostgreSQLColumnGetter) GetColumnNames(ctx context.Context, query strin
 	return columns, nil
 }
 
-// MySQLColumnGetter implements ColumnGetter for MySQL using the forked driver's StmtMetadata.
+// MySQLColumnGetter implements ColumnGetter for MySQL. Column names are read
+// from the result set metadata returned by executing the query; the test
+// tables are empty, so no real rows are transferred.
+//
+// An earlier implementation pulled column metadata straight out of a prepared
+// statement via a forked mysql driver exposing StmtMetadata. That fork
+// required a `replace` directive in go.mod, which broke `go install
+// github.com/sqlc-dev/sqlc/cmd/sqlc@latest` (see
+// https://github.com/sqlc-dev/sqlc/issues/4397). Reading columns from sql.Rows
+// works with the upstream driver and keeps the test covering the same
+// behavior.
 type MySQLColumnGetter struct {
 	db *sql.DB
 }
 
 func (g *MySQLColumnGetter) GetColumnNames(ctx context.Context, query string) ([]string, error) {
-	conn, err := g.db.Conn(ctx)
+	rows, err := g.db.QueryContext(ctx, query)
 	if err != nil {
 		return nil, err
 	}
-	defer conn.Close()
-
-	var columns []string
-	err = conn.Raw(func(driverConn any) error {
-		preparer, ok := driverConn.(driver.ConnPrepareContext)
-		if !ok {
-			return fmt.Errorf("driver connection does not support PrepareContext")
-		}
-
-		stmt, err := preparer.PrepareContext(ctx, query)
-		if err != nil {
-			return err
-		}
-		defer stmt.Close()
-
-		meta, ok := stmt.(mysql.StmtMetadata)
-		if !ok {
-			return fmt.Errorf("prepared statement does not implement StmtMetadata")
-		}
-
-		for _, col := range meta.ColumnMetadata() {
-			columns = append(columns, col.Name)
-		}
-		return nil
-	})
-	if err != nil {
-		return nil, err
-	}
-
-	return columns, nil
+	defer rows.Close()
+	return rows.Columns()
 }
 
 // SQLiteColumnGetter implements ColumnGetter for SQLite using the native ncruces/go-sqlite3 API.