chore: enable prealloc linter and address issues (testcontainers#3458)

* chore: enable prealloc linter and address issues

* lint: remove redundant zero allocations

Author: NathanBaulch

.golangci.yml

@@ -17,6 +17,7 @@ linters:
     - nakedret
     - nolintlint
     - perfsprint
+    - prealloc
     - revive
     - testifylint
     - thelper

docker.go

@@ -513,14 +513,13 @@ func (c *DockerContainer) ContainerIP(ctx context.Context) (string, error) {
 
 // ContainerIPs gets the IP addresses of all the networks within the container.
 func (c *DockerContainer) ContainerIPs(ctx context.Context) ([]string, error) {
-	ips := make([]string, 0)
-
 	inspect, err := c.Inspect(ctx)
 	if err != nil {
 		return nil, err
 	}
 
 	networks := inspect.NetworkSettings.Networks
+	ips := make([]string, 0, len(networks))
 	for _, nw := range networks {
 		ips = append(ips, nw.IPAddress)
 	}

internal/core/images.go

@@ -39,7 +39,6 @@ func ExtractImagesFromDockerfile(dockerfile string, buildArgs map[string]*string
 
 // ExtractImagesFromReader extracts images from the Dockerfile sourced from r.
 func ExtractImagesFromReader(r io.Reader, buildArgs map[string]*string) ([]string, error) {
-	var images []string
 	var lines []string
 	scanner := bufio.NewScanner(r)
 	for scanner.Scan() {
@@ -49,6 +48,8 @@ func ExtractImagesFromReader(r io.Reader, buildArgs map[string]*string) ([]strin
 		return nil, scanner.Err()
 	}
 
+	images := make([]string, 0, len(lines))
+
 	// extract images from dockerfile
 	for _, line := range lines {
 		line = strings.TrimSpace(line)

modulegen/internal/context/context.go

@@ -69,7 +69,7 @@ func (ctx Context) getModulesByBaseDir(baseDir string) ([]string, error) {
 		return nil, err
 	}
 
-	dirs := make([]string, 0)
+	var dirs []string
 
 	for _, f := range allFiles {
 		if f.IsDir() {
@@ -90,7 +90,7 @@ func (ctx Context) getMarkdownsFromDir(baseDir string) ([]string, error) {
 		return nil, err
 	}
 
-	dirs := make([]string, 0)
+	var dirs []string
 
 	for _, f := range allFiles {
 		if !f.IsDir() && filepath.Ext(f.Name()) == ".md" {

modulegen/main_test.go

@@ -297,10 +297,12 @@ func TestRefresh(t *testing.T) {
 	err := internal.Refresh(testProject.ctx)
 	require.NoError(t, err)
 
-	var modulesAndExamples []context.TestcontainersModule
-
 	examples, err := testProject.ctx.GetExamples()
 	require.NoError(t, err)
+	modules, err := testProject.ctx.GetModules()
+	require.NoError(t, err)
+
+	modulesAndExamples := make([]context.TestcontainersModule, 0, len(examples)+len(modules))
 
 	for _, example := range examples {
 		modulesAndExamples = append(modulesAndExamples, context.TestcontainersModule{
@@ -309,9 +311,6 @@ func TestRefresh(t *testing.T) {
 		})
 	}
 
-	modules, err := testProject.ctx.GetModules()
-	require.NoError(t, err)
-
 	for _, module := range modules {
 		modulesAndExamples = append(modulesAndExamples, context.TestcontainersModule{
 			Name:     module,

modules/cassandra/cassandra.go

@@ -45,8 +45,8 @@ func WithConfigFile(configFile string) testcontainers.CustomizeRequestOption {
 // WithInitScripts sets the init cassandra queries to be run when the container starts
 func WithInitScripts(scripts ...string) testcontainers.CustomizeRequestOption {
 	return func(req *testcontainers.GenericContainerRequest) error {
-		var initScripts []testcontainers.ContainerFile
-		var execs []testcontainers.Executable
+		initScripts := make([]testcontainers.ContainerFile, 0, len(scripts))
+		execs := make([]testcontainers.Executable, 0, len(scripts))
 		for _, script := range scripts {
 			cf := testcontainers.ContainerFile{
 				HostFilePath:      script,

modules/couchbase/couchbase.go

@@ -66,7 +66,7 @@ func RunContainer(ctx context.Context, opts ...testcontainers.ContainerCustomize
 // Run creates an instance of the Couchbase container type
 func Run(ctx context.Context, img string, opts ...testcontainers.ContainerCustomizer) (*CouchbaseContainer, error) {
 	config := &Config{
-		enabledServices:  make([]Service, 0),
+		enabledServices:  []Service{},
 		username:         "Administrator",
 		password:         "password",
 		indexStorageMode: MemoryOptimized,

modules/dolt/dolt.go

@@ -259,7 +259,7 @@ func WithCredsFile(credsFile string) testcontainers.CustomizeRequestOption {
 
 func WithScripts(scripts ...string) testcontainers.CustomizeRequestOption {
 	return func(req *testcontainers.GenericContainerRequest) error {
-		var initScripts []testcontainers.ContainerFile
+		initScripts := make([]testcontainers.ContainerFile, 0, len(scripts))
 		for _, script := range scripts {
 			cf := testcontainers.ContainerFile{
 				HostFilePath:      script,

modules/mariadb/mariadb.go

@@ -94,7 +94,7 @@ func WithConfigFile(configFile string) testcontainers.CustomizeRequestOption {
 
 func WithScripts(scripts ...string) testcontainers.CustomizeRequestOption {
 	return func(req *testcontainers.GenericContainerRequest) error {
-		var initScripts []testcontainers.ContainerFile
+		initScripts := make([]testcontainers.ContainerFile, 0, len(scripts))
 		for _, script := range scripts {
 			cf := testcontainers.ContainerFile{
 				HostFilePath:      script,

modules/mysql/mysql.go

@@ -186,7 +186,7 @@ func WithConfigFile(configFile string) testcontainers.CustomizeRequestOption {
 
 func WithScripts(scripts ...string) testcontainers.CustomizeRequestOption {
 	return func(req *testcontainers.GenericContainerRequest) error {
-		var initScripts []testcontainers.ContainerFile
+		initScripts := make([]testcontainers.ContainerFile, 0, len(scripts))
 		for _, script := range scripts {
 			cf := testcontainers.ContainerFile{
 				HostFilePath:      script,