Allow ModuleConfig.WithName("") to clear the module name (#1277)

We currently allow clearing other config with nil, such as FSConfig.
However, we missed a spot as internally we couldn't differentiate
between name never set, or explicitly set to empty. Now, when someone
sets the module name to empty, the name in the binary section is
ignored.

Signed-off-by: Adrian Cole <adrian@tetrate.io>

config.go

@@ -455,7 +455,7 @@ type ModuleConfig interface {
 	WithFSConfig(FSConfig) ModuleConfig
 
 	// WithName configures the module name. Defaults to what was decoded from
-	// the name section.
+	// the name section. Empty string ("") clears any name.
 	WithName(string) ModuleConfig
 
 	// WithStartFunctions configures the functions to call after the module is
@@ -597,6 +597,7 @@ type ModuleConfig interface {
 
 type moduleConfig struct {
 	name               string
+	nameSet            bool
 	startFunctions     []string
 	stdin              io.Reader
 	stdout             io.Writer
@@ -685,6 +686,7 @@ func (c *moduleConfig) WithFSConfig(config FSConfig) ModuleConfig {
 // WithName implements ModuleConfig.WithName
 func (c *moduleConfig) WithName(name string) ModuleConfig {
 	ret := c.clone()
+	ret.nameSet = true
 	ret.name = name
 	return ret
 }

config_test.go

@@ -100,29 +100,50 @@ func TestRuntimeConfig(t *testing.T) {
 
 func TestModuleConfig(t *testing.T) {
 	tests := []struct {
-		name     string
-		with     func(ModuleConfig) ModuleConfig
-		expected string
+		name          string
+		with          func(ModuleConfig) ModuleConfig
+		expectNameSet bool
+		expectedName  string
 	}{
+		{
+			name: "WithName default",
+			with: func(c ModuleConfig) ModuleConfig {
+				return c
+			},
+			expectNameSet: false,
+			expectedName:  "",
+		},
 		{
 			name: "WithName",
 			with: func(c ModuleConfig) ModuleConfig {
 				return c.WithName("wazero")
 			},
-			expected: "wazero",
+			expectNameSet: true,
+			expectedName:  "wazero",
 		},
 		{
 			name: "WithName empty",
 			with: func(c ModuleConfig) ModuleConfig {
 				return c.WithName("")
 			},
+			expectNameSet: true,
+			expectedName:  "",
 		},
 		{
 			name: "WithName twice",
 			with: func(c ModuleConfig) ModuleConfig {
 				return c.WithName("wazero").WithName("wa0")
 			},
-			expected: "wa0",
+			expectNameSet: true,
+			expectedName:  "wa0",
+		},
+		{
+			name: "WithName can clear",
+			with: func(c ModuleConfig) ModuleConfig {
+				return c.WithName("wazero").WithName("")
+			},
+			expectNameSet: true,
+			expectedName:  "",
 		},
 	}
 	for _, tt := range tests {
@@ -131,7 +152,8 @@ func TestModuleConfig(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			input := NewModuleConfig()
 			rc := tc.with(input)
-			require.Equal(t, tc.expected, rc.(*moduleConfig).name)
+			require.Equal(t, tc.expectNameSet, rc.(*moduleConfig).nameSet)
+			require.Equal(t, tc.expectedName, rc.(*moduleConfig).name)
 			// The source wasn't modified
 			require.Equal(t, NewModuleConfig(), input)
 		})

runtime.go

@@ -283,7 +283,7 @@ func (r *runtime) InstantiateModule(
 	}
 
 	name := config.name
-	if name == "" && code.module.NameSection != nil && code.module.NameSection.ModuleName != "" {
+	if !config.nameSet && code.module.NameSection != nil && code.module.NameSection.ModuleName != "" {
 		name = code.module.NameSection.ModuleName
 	}
 

runtime_test.go

@@ -446,19 +446,23 @@ func TestRuntime_InstantiateModule_WithName(t *testing.T) {
 	internal := r.(*runtime)
 	m1, err := r.InstantiateModule(testCtx, base, NewModuleConfig().WithName("1"))
 	require.NoError(t, err)
+	require.Equal(t, "1", m1.Name())
 
 	require.Nil(t, internal.Module("0"))
 	require.Equal(t, internal.Module("1"), m1)
 
 	m2, err := r.InstantiateModule(testCtx, base, NewModuleConfig().WithName("2"))
 	require.NoError(t, err)
+	require.Equal(t, "2", m2.Name())
 
 	require.Nil(t, internal.Module("0"))
 	require.Equal(t, internal.Module("2"), m2)
 
 	// Empty name module shouldn't be returned via Module() for future optimization.
-	_, err = r.InstantiateModule(testCtx, base, NewModuleConfig().WithName(""))
+	m3, err := r.InstantiateModule(testCtx, base, NewModuleConfig().WithName(""))
 	require.NoError(t, err)
+	require.Equal(t, "", m3.Name())
+
 	ret := internal.Module("")
 	require.Nil(t, ret)
 }