Fixes MySQL copyfrom generation with 1 arg stucts (#3446)

* Updated MySQL copyfrom template to handle strucs with 1 argument

* Added copyfrom 1 arg struct testcase

* Fixed issue where copyfrom structs were not being emitted

* Added testcase to catch not emitting structs used with copyfrom

Author: terricain

internal/codegen/golang/result.go

@@ -259,7 +259,9 @@ func buildQueries(req *plugin.GenerateRequest, options *opts.Options, structs []
 				EmitPointer: options.EmitParamsStructPointers,
 			}
 
-			if len(query.Params) <= qpl {
+			// if query params is 2, and query params limit is 4 AND this is a copyfrom, we still want to emit the query's model
+			// otherwise we end up with a copyfrom using a struct without the struct definition
+			if len(query.Params) <= qpl && query.Cmd != ":copyfrom" {
 				gq.Arg.Emit = false
 			}
 		}

internal/codegen/golang/templates/go-sql-driver-mysql/copyfromCopy.tmpl

@@ -9,11 +9,11 @@ func convertRowsFor{{.MethodName}}(w *io.PipeWriter, {{.Arg.SlicePair}}) {
 {{- with $arg := .Arg }}
 {{- range $arg.CopyFromMySQLFields}}
 {{- if eq .Type "string"}}
-	e.AppendString({{if eq (len $arg.CopyFromMySQLFields) 1}}row{{else}}row.{{.Name}}{{end}})
+	e.AppendString({{if $arg.Struct}}row.{{.Name}}{{else}}row{{end}})
 {{- else if or (eq .Type "[]byte") (eq .Type "json.RawMessage")}}
-	e.AppendBytes({{if eq (len $arg.CopyFromMySQLFields) 1}}row{{else}}row.{{.Name}}{{end}})
+	e.AppendBytes({{if $arg.Struct}}row.{{.Name}}{{else}}row{{end}})
 {{- else}}
-	e.AppendValue({{if eq (len $arg.CopyFromMySQLFields) 1}}row{{else}}row.{{.Name}}{{end}})
+	e.AppendValue({{if $arg.Struct}}row.{{.Name}}{{else}}row{{end}})
 {{- end}}
 {{- end}}
 {{- end}}

internal/endtoend/testdata/copyfrom_multicolumn_parameter_limit/mysql/go/copyfrom.go

@@ -0,0 +1,2 @@
+-- name: InsertMultipleValues :copyfrom
+INSERT INTO foo (a, b) VALUES (?, ?);

internal/endtoend/testdata/copyfrom_multicolumn_parameter_limit/mysql/go/db.go

@@ -0,0 +1 @@
+CREATE TABLE foo (a text, b text);

internal/endtoend/testdata/copyfrom_multicolumn_parameter_limit/mysql/go/models.go

@@ -0,0 +1,15 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "sql_package": "database/sql",
+      "sql_driver": "github.com/go-sql-driver/mysql",
+      "engine": "mysql",
+      "name": "querytest",
+      "schema": "schema.sql",
+      "queries": "query.sql",
+      "query_parameter_limit": 4
+    }
+  ]
+}

internal/endtoend/testdata/copyfrom_multicolumn_parameter_limit/mysql/go/query.sql.go

@@ -0,0 +1 @@
+https://github.com/sqlc-dev/sqlc/issues/3443

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

@@ -0,0 +1,2 @@
+-- name: InsertSingleValue :copyfrom
+INSERT INTO foo (a) VALUES (?);

internal/endtoend/testdata/copyfrom_multicolumn_parameter_limit/mysql/schema.sql

@@ -0,0 +1 @@
+CREATE TABLE foo (a text);

internal/endtoend/testdata/copyfrom_multicolumn_parameter_limit/mysql/sqlc.json

@@ -0,0 +1,15 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "sql_package": "database/sql",
+      "sql_driver": "github.com/go-sql-driver/mysql",
+      "engine": "mysql",
+      "name": "querytest",
+      "schema": "schema.sql",
+      "queries": "query.sql",
+      "query_parameter_limit": 0
+    }
+  ]
+}