Add a noexprlang build tag

This modules uses `github.com/expr-lang/expr` which, because of the
extensive use of the `reflect` package, disables go's compiler dead code
elimination which can lead to bigger binaries.

This commit adds a `noexprlang` build tag that allows jsm.go users that
do not use expression matching to entirely disable the use of the expr
module so that they can benefit from go's dead code elimination if they
are eligible to outside jsm.go.

References:
- https://golab.io/talks/getting-the-most-out-of-dead-code-elimination
- https://github.com/aarzilli/whydeadcode
- spf13/cobra#1956

Signed-off-by: Sylvain Rabot <[email protected]>

README.md

@@ -178,7 +178,7 @@ mgr, _ := jsm.New(nc, jsm.WithAPIValidation(new(SchemaValidator)))
 
 ## Build tag
 
-This library provide a `noexprlang` build tag that disables expression matching
-for Streams and Consumers listing. The purpose of this build tag is to disable
+This library provides a `noexprlang` build tag that disables expression matching
+for Streams and Consumers queries. The purpose of this build tag is to disable
 the use of the `github.com/expr-lang/expr` module that disables go compiler's dead
 code elimination because it uses some types and functions of the `reflect` package.

consumer_query.go

@@ -57,14 +57,6 @@ func ConsumerQueryApiLevelMin(level int) ConsumerQueryOpt {
 	}
 }
 
-// ConsumerQueryExpression filters the consumers using the expr expression language
-func ConsumerQueryExpression(e string) ConsumerQueryOpt {
-	return func(q *consumerQuery) error {
-		q.expression = e
-		return nil
-	}
-}
-
 // ConsumerQueryLeaderServer finds clustered consumers where a certain node is the leader
 func ConsumerQueryLeaderServer(server string) ConsumerQueryOpt {
 	return func(q *consumerQuery) error {

jsm.go

@@ -31,6 +31,10 @@ import (
 	"github.com/nats-io/jsm.go/api"
 )
 
+// ErrNoExprLangBuild warns that expression matching is disabled when compiling
+// a go binary with the `noexprlang` build tag.
+var ErrNoExprLangBuild = fmt.Errorf("binary has been built with `noexprlang` build tag and thus does not support expression matching")
+
 // standard api responses with error embedded
 type jetStreamResponseError interface {
 	ToError() error

match.go

@@ -9,6 +9,16 @@ import (
 	"gopkg.in/yaml.v3"
 )
 
+// StreamQueryExpression filters the stream using the expr expression language
+// Using this option with a binary built with the `noexprlang` build tag will
+// always return [ErrNoExprLangBuild].
+func StreamQueryExpression(e string) StreamQueryOpt {
+	return func(q *streamQuery) error {
+		q.expression = e
+		return nil
+	}
+}
+
 func (q *streamQuery) matchExpression(streams []*Stream) ([]*Stream, error) {
 	if q.expression == "" {
 		return streams, nil
@@ -59,6 +69,16 @@ func (q *streamQuery) matchExpression(streams []*Stream) ([]*Stream, error) {
 	return matched, nil
 }
 
+// ConsumerQueryExpression filters the consumers using the expr expression language
+// Using this option with a binary built with the `noexprlang` build tag will
+// always return [ErrNoExprLangBuild].
+func ConsumerQueryExpression(e string) ConsumerQueryOpt {
+	return func(q *consumerQuery) error {
+		q.expression = e
+		return nil
+	}
+}
+
 func (q *consumerQuery) matchExpression(consumers []*Consumer) ([]*Consumer, error) {
 	if q.expression == "" {
 		return consumers, nil

match_noexpr.go

@@ -2,16 +2,36 @@
 
 package jsm
 
-import "fmt"
-
-// ErrNoExprLangBuild warns that expression matching is disabled when compiling
-// a go binary with the `noexprlang` build tag.
-var ErrNoExprLangBuild = fmt.Errorf("binary has been built with `noexprlang` build tag and thus does not support expression matching")
+// StreamQueryExpression filters the stream using the expr expression language
+// Using this option with a binary built with the `noexprlang` build tag will
+// always return [ErrNoExprLangBuild].
+func StreamQueryExpression(e string) StreamQueryOpt {
+	return func(q *streamQuery) error {
+		q.expression = e
+		return ErrNoExprLangBuild
+	}
+}
 
 func (q *streamQuery) matchExpression(streams []*Stream) ([]*Stream, error) {
+	if q.expression == "" {
+		return streams, nil
+	}
 	return nil, ErrNoExprLangBuild
 }
 
+// ConsumerQueryExpression filters the consumers using the expr expression language
+// Using this option with a binary built with the `noexprlang` build tag will
+// always return [ErrNoExprLangBuild].
+func ConsumerQueryExpression(e string) ConsumerQueryOpt {
+	return func(q *consumerQuery) error {
+		q.expression = e
+		return ErrNoExprLangBuild
+	}
+}
+
 func (q *consumerQuery) matchExpression(consumers []*Consumer) ([]*Consumer, error) {
+	if q.expression == "" {
+		return consumers, nil
+	}
 	return nil, ErrNoExprLangBuild
 }

stream_query.go

@@ -54,14 +54,6 @@ func StreamQueryApiLevelMin(level int) StreamQueryOpt {
 	}
 }
 
-// StreamQueryExpression filters the stream using the expr expression language
-func StreamQueryExpression(e string) StreamQueryOpt {
-	return func(q *streamQuery) error {
-		q.expression = e
-		return nil
-	}
-}
-
 func StreamQueryIsSourced() StreamQueryOpt {
 	return func(q *streamQuery) error {
 		q.sourced = true