common: Fix URL parsing issues on Windows

CHANGELOG.md

@@ -28,6 +28,7 @@ IMPROVEMENTS:
 BUG FIXES:
 
   * core: Errors are properly shown when adding bad floppy files. [GH-1043]
+  * core: Fix some URL parsing issues on Windows.
   * builder/amazon-instance: Use S3Endpoint for ec2-upload-bundle arg,
       which works for every region. [GH-904]
   * builder/digitalocean: updated default image_id [GH-1032]

common/config.go

@@ -101,15 +101,20 @@ func DownloadableURL(original string) (string, error) {
 	}
 
 	if url.Scheme == "file" {
-		// For Windows absolute file paths, remove leading / prior to processing
-		// since net/url turns "C:/" into "/C:/"
-		if runtime.GOOS == "windows" && url.Path[0] == '/' {
-			url.Path = url.Path[1:len(url.Path)]
+		// Windows file handling is all sorts of tricky...
+		if runtime.GOOS == "windows" {
+			// If the path is using Windows-style slashes, URL parses
+			// it into the host field.
+			if url.Path == "" && strings.Contains(url.Host, `\`) {
+				url.Path = url.Host
+				url.Host = ""
+			}
 
-			// Also replace all backslashes with forwardslashes since Windows
-			// users are likely to do this but the URL should actually only
-			// contain forward slashes.
-			url.Path = strings.Replace(url.Path, `\`, `/`, -1)
+			// For Windows absolute file paths, remove leading / prior to processing
+			// since net/url turns "C:/" into "/C:/"
+			if len(url.Path) > 0 && url.Path[0] == '/' {
+				url.Path = url.Path[1:len(url.Path)]
+			}
 		}
 
 		// Only do the filepath transformations if the file appears
@@ -127,6 +132,13 @@ func DownloadableURL(original string) (string, error) {
 
 			url.Path = filepath.Clean(url.Path)
 		}
+
+		if runtime.GOOS == "windows" {
+			// Also replace all backslashes with forwardslashes since Windows
+			// users are likely to do this but the URL should actually only
+			// contain forward slashes.
+			url.Path = strings.Replace(url.Path, `\`, `/`, -1)
+		}
 	}
 
 	// Make sure it is lowercased
@@ -195,11 +207,13 @@ func decodeConfigHook(raws []interface{}) (mapstructure.DecodeHookFunc, error) {
 	}, nil
 }
 
-func CoalesceVals(vals ...string) string {
+// ChooseString returns the first non-empty value.
+func ChooseString(vals ...string) string {
     for _, el := range vals {
         if el != "" {
             return el
         }
     }
+
     return ""
 }

common/config_test.go

@@ -7,6 +7,8 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"runtime"
+	"strings"
 	"testing"
 )
 
@@ -141,6 +143,11 @@ func TestDownloadableURL_FilePaths(t *testing.T) {
 
 	tfPath = filepath.Clean(tfPath)
 
+	filePrefix := "file://"
+	if runtime.GOOS == "windows" {
+		filePrefix += "/"
+	}
+
 	// Relative filepath. We run this test in a func so that
 	// the defers run right away.
 	func() {
@@ -161,8 +168,11 @@ func TestDownloadableURL_FilePaths(t *testing.T) {
 			t.Fatalf("err: %s", err)
 		}
 
-		if u != fmt.Sprintf("file://%s", tfPath) {
-			t.Fatalf("unexpected: %s", u)
+		expected := fmt.Sprintf("%s%s",
+			filePrefix,
+			strings.Replace(tfPath, `\`, `/`, -1))
+		if u != expected {
+			t.Fatalf("unexpected: %#v != %#v", u, expected)
 		}
 	}()
 
@@ -180,8 +190,11 @@ func TestDownloadableURL_FilePaths(t *testing.T) {
 			t.Fatalf("err: %s", err)
 		}
 
-		if u != fmt.Sprintf("file://%s", tfPath) {
-			t.Fatalf("unexpected: %s", u)
+		expected := fmt.Sprintf("%s%s",
+			filePrefix,
+			strings.Replace(tfPath, `\`, `/`, -1))
+		if u != expected {
+			t.Fatalf("unexpected: %s != %s", u, expected)
 		}
 	}
 }