internal/codegen/golang: simplify template tag condition

Rather than modeling when .Tag will be empty,
check directly whether .Tag is empty.

This simplifies the template and reduces the number
of places that must be touched when adding new
sources of struct tags.

Author: josharian

internal/codegen/golang/templates/pgx/batchCode.tmpl

@@ -12,14 +12,14 @@ type {{.MethodName}}BatchResults struct {
 
 {{if .Arg.EmitStruct}}
 type {{.Arg.Type}} struct { {{- range .Arg.Struct.Fields}}
-  {{.Name}} {{.Type}} {{if or ($.EmitJSONTags) ($.EmitDBTags)}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
+  {{.Name}} {{.Type}} {{if .Tag}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
   {{- end}}
 }
 {{end}}
 
 {{if .Ret.EmitStruct}}
 type {{.Ret.Type}} struct { {{- range .Ret.Struct.Fields}}
-  {{.Name}} {{.Type}} {{if or ($.EmitJSONTags) ($.EmitDBTags)}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
+  {{.Name}} {{.Type}} {{if .Tag}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
   {{- end}}
 }
 {{end}}

internal/codegen/golang/templates/pgx/queryCode.tmpl

@@ -10,14 +10,14 @@ const {{.ConstantName}} = {{$.Q}}-- name: {{.MethodName}} {{.Cmd}}
 {{if ne (hasPrefix .Cmd ":batch") true}}
 {{if .Arg.EmitStruct}}
 type {{.Arg.Type}} struct { {{- range .Arg.Struct.Fields}}
-  {{.Name}} {{.Type}} {{if or ($.EmitJSONTags) ($.EmitDBTags)}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
+  {{.Name}} {{.Type}} {{if .Tag}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
   {{- end}}
 }
 {{end}}
 
 {{if .Ret.EmitStruct}}
 type {{.Ret.Type}} struct { {{- range .Ret.Struct.Fields}}
-  {{.Name}} {{.Type}} {{if or ($.EmitJSONTags) ($.EmitDBTags)}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
+  {{.Name}} {{.Type}} {{if .Tag}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
   {{- end}}
 }
 {{end}}

internal/codegen/golang/templates/stdlib/queryCode.tmpl

@@ -7,14 +7,14 @@ const {{.ConstantName}} = {{$.Q}}-- name: {{.MethodName}} {{.Cmd}}
 
 {{if .Arg.EmitStruct}}
 type {{.Arg.Type}} struct { {{- range .Arg.UniqueFields}}
-  {{.Name}} {{.Type}} {{if or ($.EmitJSONTags) ($.EmitDBTags)}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
+  {{.Name}} {{.Type}} {{if .Tag}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
   {{- end}}
 }
 {{end}}
 
 {{if .Ret.EmitStruct}}
 type {{.Ret.Type}} struct { {{- range .Ret.Struct.Fields}}
-  {{.Name}} {{.Type}} {{if or ($.EmitJSONTags) ($.EmitDBTags)}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
+  {{.Name}} {{.Type}} {{if .Tag}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
   {{- end}}
 }
 {{end}}

internal/codegen/golang/templates/template.tmpl

@@ -94,7 +94,7 @@ type {{.Name}} struct { {{- range .Fields}}
   {{- if .Comment}}
   {{comment .Comment}}{{else}}
   {{- end}}
-  {{.Name}} {{.Type}} {{if or ($.EmitJSONTags) ($.EmitDBTags)}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
+  {{.Name}} {{.Type}} {{if .Tag}}{{$.Q}}{{.Tag}}{{$.Q}}{{end}}
   {{- end}}
 }
 {{end}}