fix(golang-rewrite): allow directories returned by list-bin-paths to be absent from the file system

* create `repotest.WritePluginCallback` function
* add test for `list-bin-paths` callback that returns non-existent path
* if directory name returned by `list-bin-paths` doesn't exist skip it

internal/shims/shims.go

@@ -308,9 +308,10 @@ func ToolExecutables(conf config.Config, plugin plugins.Plugin, versionType, ver
 
 	for _, path := range paths {
 		entries, err := os.ReadDir(path)
-		if err != nil {
+		if _, ok := err.(*os.PathError); err != nil && !ok {
 			return executables, err
 		}
+
 		for _, entry := range entries {
 			// If entry is dir or cannot be executed by the current user ignore it
 			filePath := filepath.Join(path, entry.Name())
@@ -320,9 +321,6 @@ func ToolExecutables(conf config.Config, plugin plugins.Plugin, versionType, ver
 
 			executables = append(executables, filePath)
 		}
-		if err != nil {
-			return executables, err
-		}
 	}
 	return executables, err
 }

internal/shims/shims_test.go

@@ -318,6 +318,22 @@ func TestToolExecutables(t *testing.T) {
 
 		assert.Equal(t, filenames, []string{"dummy"})
 	})
+
+	t.Run("returns list of executables even when one directory printed by list-bin-paths doesn't exist", func(t *testing.T) {
+		// foo is first in list returned by list-bin-paths but doesn't exist, do
+		// we still get the executables in the bin/ dir?
+		repotest.WritePluginCallback(plugin.Dir, "list-bin-paths", "#!/usr/bin/env bash\necho 'foo bin'")
+		executables, err := ToolExecutables(conf, plugin, "version", version.Value)
+		assert.Nil(t, err)
+
+		var filenames []string
+		for _, executablePath := range executables {
+			assert.True(t, strings.HasPrefix(executablePath, conf.DataDir))
+			filenames = append(filenames, filepath.Base(executablePath))
+		}
+
+		assert.Equal(t, filenames, []string{"dummy"})
+	})
 }
 
 func TestExecutableDirs(t *testing.T) {

repotest/repotest.go

@@ -31,6 +31,11 @@ func Setup(asdfDataDir string) error {
 	return nil
 }
 
+// WritePluginCallback is for creating new plugin callbacks on the fly.
+func WritePluginCallback(pluginDir, callbackName, script string) error {
+	return os.WriteFile(filepath.Join(pluginDir, "bin", callbackName), []byte(script), 0o777)
+}
+
 // InstallPlugin copies in the specified plugin fixture into the asdfDataDir's
 // plugin directory and initializes a Git repo for it so asdf treats it as
 // installed.