Remove the word middleware (#1067)

* Rename middleware to plugin

first pass; mostly used 'sed', few spots where I manually changed
text.

This still builds a coredns binary.

* fmt error

* Rename AddMiddleware to AddPlugin

* Readd AddMiddleware to remain backwards compat

plugin/root/README.md

@@ -0,0 +1,22 @@
+# root
+
+*root* simply specifies the root of where CoreDNS finds (e.g.) zone files.
+
+The default root is the current working directory of CoreDNS. A relative root path is relative to
+the current working directory.
+
+## Syntax
+
+~~~ txt
+root PATH
+~~~
+
+**PATH** is the directory to set as CoreDNS' root.
+
+## Examples
+
+Serve zone data (when the *file* plugin is used) from `/etc/coredns/zones`:
+
+~~~ txt
+root /etc/coredns/zones
+~~~

plugin/root/root.go

@@ -0,0 +1,43 @@
+package root
+
+import (
+	"log"
+	"os"
+
+	"github.com/coredns/coredns/core/dnsserver"
+	"github.com/coredns/coredns/plugin"
+
+	"github.com/mholt/caddy"
+)
+
+func init() {
+	caddy.RegisterPlugin("root", caddy.Plugin{
+		ServerType: "dns",
+		Action:     setup,
+	})
+}
+
+func setup(c *caddy.Controller) error {
+	config := dnsserver.GetConfig(c)
+
+	for c.Next() {
+		if !c.NextArg() {
+			return plugin.Error("root", c.ArgErr())
+		}
+		config.Root = c.Val()
+	}
+
+	// Check if root path exists
+	_, err := os.Stat(config.Root)
+	if err != nil {
+		if os.IsNotExist(err) {
+			// Allow this, because the folder might appear later.
+			// But make sure the user knows!
+			log.Printf("[WARNING] Root path does not exist: %s", config.Root)
+		} else {
+			return plugin.Error("root", c.Errf("unable to access root path '%s': %v", config.Root, err))
+		}
+	}
+
+	return nil
+}

plugin/root/root_test.go

@@ -0,0 +1,107 @@
+package root
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/coredns/coredns/core/dnsserver"
+
+	"github.com/mholt/caddy"
+)
+
+func TestRoot(t *testing.T) {
+	log.SetOutput(ioutil.Discard)
+
+	// Predefined error substrings
+	parseErrContent := "Error during parsing:"
+	unableToAccessErrContent := "unable to access root path"
+
+	existingDirPath, err := getTempDirPath()
+	if err != nil {
+		t.Fatalf("BeforeTest: Failed to find an existing directory for testing! Error was: %v", err)
+	}
+
+	nonExistingDir := filepath.Join(existingDirPath, "highly_unlikely_to_exist_dir")
+
+	existingFile, err := ioutil.TempFile("", "root_test")
+	if err != nil {
+		t.Fatalf("BeforeTest: Failed to create temp file for testing! Error was: %v", err)
+	}
+	defer func() {
+		existingFile.Close()
+		os.Remove(existingFile.Name())
+	}()
+
+	inaccessiblePath := getInaccessiblePath(existingFile.Name())
+
+	tests := []struct {
+		input              string
+		shouldErr          bool
+		expectedRoot       string // expected root, set to the controller. Empty for negative cases.
+		expectedErrContent string // substring from the expected error. Empty for positive cases.
+	}{
+		// positive
+		{
+			fmt.Sprintf(`root %s`, nonExistingDir), false, nonExistingDir, "",
+		},
+		{
+			fmt.Sprintf(`root %s`, existingDirPath), false, existingDirPath, "",
+		},
+		// negative
+		{
+			`root `, true, "", parseErrContent,
+		},
+		{
+			fmt.Sprintf(`root %s`, inaccessiblePath), true, "", unableToAccessErrContent,
+		},
+		{
+			fmt.Sprintf(`root {
+				%s
+			}`, existingDirPath), true, "", parseErrContent,
+		},
+	}
+
+	for i, test := range tests {
+		c := caddy.NewTestController("dns", test.input)
+		err := setup(c)
+		cfg := dnsserver.GetConfig(c)
+
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %d: Expected error but found %s for input %s", i, err, test.input)
+		}
+
+		if err != nil {
+			if !test.shouldErr {
+				t.Errorf("Test %d: Expected no error but found one for input %s. Error was: %v", i, test.input, err)
+			}
+
+			if !strings.Contains(err.Error(), test.expectedErrContent) {
+				t.Errorf("Test %d: Expected error to contain: %v, found error: %v, input: %s", i, test.expectedErrContent, err, test.input)
+			}
+		}
+
+		// check root only if we are in a positive test.
+		if !test.shouldErr && test.expectedRoot != cfg.Root {
+			t.Errorf("Root not correctly set for input %s. Expected: %s, actual: %s", test.input, test.expectedRoot, cfg.Root)
+		}
+	}
+}
+
+// getTempDirPath returnes the path to the system temp directory. If it does not exists - an error is returned.
+func getTempDirPath() (string, error) {
+	tempDir := os.TempDir()
+	_, err := os.Stat(tempDir)
+	if err != nil {
+		return "", err
+	}
+	return tempDir, nil
+}
+
+func getInaccessiblePath(file string) string {
+	return filepath.Join("C:", "file\x00name") // null byte in filename is not allowed on Windows AND unix
+}