Fix unused imports for Go code generator (#722)

* Fix unused imports for Go generator

For ":cmd" queries, the return type should not be imported.

* Add e2e test

Tests the patch for unused imports.

Author: soroushj

internal/codegen/golang/imports.go

@@ -94,7 +94,7 @@ func (i *importer) dbImports() fileImports {
 func (i *importer) interfaceImports() fileImports {
 	uses := func(name string) bool {
 		for _, q := range i.Queries {
-			if !q.Ret.isEmpty() {
+			if q.hasRetType() {
 				if strings.HasPrefix(q.Ret.Type(), name) {
 					return true
 				}
@@ -244,7 +244,7 @@ func (i *importer) queryImports(filename string) fileImports {
 
 	uses := func(name string) bool {
 		for _, q := range gq {
-			if !q.Ret.isEmpty() {
+			if q.hasRetType() {
 				if q.Ret.EmitStruct() {
 					for _, f := range q.Ret.Struct.Fields {
 						fType := strings.TrimPrefix(f.Type, "[]")
@@ -276,7 +276,7 @@ func (i *importer) queryImports(filename string) fileImports {
 
 	sliceScan := func() bool {
 		for _, q := range gq {
-			if !q.Ret.isEmpty() {
+			if q.hasRetType() {
 				if q.Ret.IsStruct() {
 					for _, f := range q.Ret.Struct.Fields {
 						if strings.HasPrefix(f.Type, "[]") && f.Type != "[]byte" {

internal/codegen/golang/query.go

@@ -101,3 +101,7 @@ type Query struct {
 	Ret          QueryValue
 	Arg          QueryValue
 }
+
+func (q Query) hasRetType() bool {
+	return q.Cmd != ":exec" && !q.Ret.isEmpty()
+}

internal/endtoend/testdata/exec_imports/go/db.go

@@ -0,0 +1,9 @@
+CREATE TABLE foo (bar int, bars int[] not null);
+
+-- name: Bar :exec
+SELECT bar
+FROM foo;
+
+-- name: Bars :exec
+SELECT bars
+FROM foo;

internal/endtoend/testdata/exec_imports/go/models.go

@@ -0,0 +1,12 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "name": "querytest",
+      "schema": "query.sql",
+      "queries": "query.sql",
+      "emit_interface": true
+    }
+  ]
+}