fspath: Implement a connection string parser #4996

This is implemented as a state machine parser so it can emit sensible
error messages.

It does not use the connection strings elsewhere in rclone yet - see
subsequent commits.

An optional fuzzer is implemented for the Parse function.

backend/chunker/chunker.go

@@ -277,10 +277,11 @@ func NewFs(ctx context.Context, name, rpath string, m configmap.Mapper) (fs.Fs,
 		return nil, errors.New("can't point remote at itself - check the value of the remote setting")
 	}
 
-	baseName, basePath, err := fspath.Parse(remote)
+	parsed, err := fspath.Parse(remote)
 	if err != nil {
 		return nil, errors.Wrapf(err, "failed to parse remote %q to wrap", remote)
 	}
+	baseName, basePath := parsed.ConfigString, parsed.Path
 	if baseName != "" {
 		baseName += ":"
 	}

docs/content/docs.md

@@ -208,6 +208,83 @@ To copy files and directories in `https://example.com/path/to/dir` to `/tmp/dir`
 To copy files and directories from `example.com` in the relative
 directory `path/to/dir` to `/tmp/dir` using sftp.
 
+### Connection strings {#connection-strings}
+
+The above examples can also be written using a connection string
+syntax, so instead of providing the arguments as command line
+parameters `--http-url https://pub.rclone.org` they are provided as
+part of the remote specification as a kind of connection string.
+
+    rclone lsd ":http,url='https://pub.rclone.org':"
+    rclone lsf ":http,url='https://example.com':path/to/dir"
+    rclone copy ":http,url='https://example.com':path/to/dir" /tmp/dir
+    rclone copy :sftp,host=example.com:path/to/dir /tmp/dir
+
+These can apply to modify existing remotes as well as create new
+remotes with the on the fly syntax. This example is equivalent to
+adding the `--drive-shared-with-me` parameter to the remote `gdrive:`.
+
+    rclone lsf "gdrive,shared_with_me:path/to/dir"
+
+The major advantage to using the connection string style syntax is
+that it only applies the the remote, not to all the remotes of that
+type of the command line. A common confusion is this attempt to copy a
+file shared on google drive to the normal drive which **does not
+work** because the `--drive-shared-with-me` flag applies to both the
+source and the destination.
+
+    rclone copy --drive-shared-with-me gdrive:shared-file.txt gdrive:
+
+However using the connection string syntax, this does work.
+
+    rclone copy "gdrive,shared_with_me:shared-file.txt" gdrive:
+
+The connection strings have the following syntax
+
+    remote,parameter=value,parameter2=value2:path/to/dir
+    :backend,parameter=value,parameter2=value2:path/to/dir
+
+If the `parameter` has a `:` or `,` then it must be placed in quotes `"` or
+`'`, so
+
+    remote,parameter="colon:value",parameter2="comma,value":path/to/dir
+    :backend,parameter='colon:value',parameter2='comma,value':path/to/dir
+
+If a quoted value needs to include that quote, then it should be
+doubled, so
+
+    remote,parameter="with""quote",parameter2='with''quote':path/to/dir
+
+This will make `parameter` be `with"quote` and `parameter2` be
+`with'quote`.
+
+If you leave off the `=parameter` then rclone will substitute `=true`
+which works very well with flags. For example to use s3 configured in
+the environment you could use:
+
+    rclone lsd :s3,env_auth:
+
+Which is equivalent to
+
+    rclone lsd :s3,env_auth=true:
+
+Note that on the command line you might need to surround these
+connection strings with `"` or `'` to stop the shell interpreting any
+special characters within them.
+
+If you are a shell master then you'll know which strings are OK and
+which aren't, but if you aren't sure then enclose them in `"` and use
+`'` as the inside quote. This syntax works on all OSes.
+
+    rclone copy ":http,url='https://example.com':path/to/dir" /tmp/dir
+
+On Linux/macOS some characters are still interpreted inside `"`
+strings in the shell (notably `\` and `$` and `"`) so if your strings
+contain those you can swap the roles of `"` and `'` thus. (This syntax
+does not work on Windows.)
+
+    rclone copy ':http,url="https://example.com":path/to/dir' /tmp/dir
+
 ### Valid remote names
 
  - Remote names may only contain 0-9, A-Z ,a-z ,_ , - and space.
@@ -1927,11 +2004,8 @@ so they take exactly the same form.
 ### Config file ###
 
 You can set defaults for values in the config file on an individual
-remote basis.  If you want to use this feature, you will need to
+remote basis. The names of the config items are documented in the page
-discover the name of the config items that you want.  The easiest way
+for each backend.
-is to run through `rclone config` by hand, then look in the config
-file to see what the values are (the config file can be found by
-looking at the help for `--config` in `rclone help`).
 
 To find the name of the environment variable, you need to set, take
 `RCLONE_CONFIG_` + name of remote + `_` + name of config file option
@@ -1953,6 +2027,11 @@ mys3:
 Note that if you want to create a remote using environment variables
 you must create the `..._TYPE` variable as above.
 
+Note also that now rclone has [connectionstrings](#connection-strings),
+it is probably easier to use those instead which makes the above example
+
+    rclone lsd :s3,access_key_id=XXX,secret_access_key=XXX:
+
 ### Precedence
 
 The various different methods of backend configuration are read in

fs/fs.go

@@ -1206,10 +1206,12 @@ func MustFind(name string) *RegInfo {
 // ParseRemote deconstructs a path into configName, fsPath, looking up
 // the fsName in the config file (returning NotFoundInConfigFile if not found)
 func ParseRemote(path string) (fsInfo *RegInfo, configName, fsPath string, err error) {
-	configName, fsPath, err = fspath.Parse(path)
+	parsed, err := fspath.Parse(path)
 	if err != nil {
 		return nil, "", "", err
 	}
+	configName, fsPath = parsed.Name, parsed.Path
+	// FIXME do something with parsed.Config
 	var fsName string
 	var ok bool
 	if configName != "" {

fs/fspath/fuzz.go

@@ -0,0 +1,46 @@
+//+build gofuzz
+
+/*
+   Fuzz test the Parse function
+
+   Generate corpus
+
+   go test -v -make-corpus
+
+   Install go fuzz
+
+   go get -u github.com/dvyukov/go-fuzz/go-fuzz github.com/dvyukov/go-fuzz/go-fuzz-build
+
+   Compile and fuzz
+
+   go-fuzz-build
+   go-fuzz
+
+   Tidy up
+
+   rm -rf corpus/ crashers/ suppressions/
+   git co ../../go.mod ../../go.sum
+*/
+
+package fspath
+
+func Fuzz(data []byte) int {
+	path := string(data)
+	parsed, err := Parse(path)
+	if err != nil {
+		return 0
+	}
+	if parsed.Name == "" {
+		if parsed.ConfigString != "" {
+			panic("bad ConfigString")
+		}
+		if parsed.Path != path {
+			panic("local path not preserved")
+		}
+	} else {
+		if parsed.ConfigString+":"+parsed.Path != path {
+			panic("didn't split properly")
+		}
+	}
+	return 0
+}

fs/fspath/path.go

@@ -8,28 +8,37 @@ import (
 	"regexp"
 	"strings"
 
+	"github.com/rclone/rclone/fs/config/configmap"
 	"github.com/rclone/rclone/fs/driveletter"
 )
 
 const (
 	configNameRe = `[\w_ -]+`
-	remoteNameRe = `^(:?` + configNameRe + `):`
+	remoteNameRe = `^(:?` + configNameRe + `)`
 )
 
 var (
-	errInvalidCharacters = errors.New("config name contains invalid characters - may only contain 0-9, A-Z ,a-z ,_ , - and space")
+	errInvalidCharacters = errors.New("config name contains invalid characters - may only contain `0-9`, `A-Z`, `a-z`, `_`, `-` and space")
 	errCantBeEmpty       = errors.New("can't use empty string as a path")
-	errCantStartWithDash = errors.New("config name starts with -")
+	errCantStartWithDash = errors.New("config name starts with `-`")
-
+	errBadConfigParam    = errors.New("config parameters may only contain `0-9`, `A-Z`, `a-z` and `_`")
-	// urlMatcher is a pattern to match an rclone URL
+	errEmptyConfigParam  = errors.New("config parameters can't be empty")
-	// note that this matches invalid remoteNames
+	errConfigNameEmpty   = errors.New("config name can't be empty")
-	urlMatcher = regexp.MustCompile(`^(:?[^\\/:]*):(.*)$`)
+	errConfigName        = errors.New("config name needs a trailing `:`")
+	errParam             = errors.New("config parameter must end with `,` or `:`")
+	errValue             = errors.New("unquoted config value must end with `,` or `:`")
+	errQuotedValue       = errors.New("unterminated quoted config value")
+	errAfterQuote        = errors.New("expecting `:` or `,` or another quote after a quote")
+	errSyntax            = errors.New("syntax error in config string")
 
 	// configNameMatcher is a pattern to match an rclone config name
 	configNameMatcher = regexp.MustCompile(`^` + configNameRe + `$`)
 
-	// remoteNameMatcher is a pattern to match an rclone remote name
+	// remoteNameMatcher is a pattern to match an rclone remote name at the start of a config
-	remoteNameMatcher = regexp.MustCompile(remoteNameRe + `$`)
+	remoteNameMatcher = regexp.MustCompile(`^` + remoteNameRe + `(:$|,)`)
+
+	// Function to check if string is a drive letter to be overriden in the tests
+	isDriveLetter = driveletter.IsDriveLetter
 )
 
 // CheckConfigName returns an error if configName is invalid
@@ -44,41 +53,210 @@ func CheckConfigName(configName string) error {
 	return nil
 }
 
-// CheckRemoteName returns an error if remoteName is invalid
+// checkRemoteName returns an error if remoteName is invalid
-func CheckRemoteName(remoteName string) error {
+func checkRemoteName(remoteName string) error {
+	if remoteName == ":" || remoteName == "::" {
+		return errConfigNameEmpty
+	}
 	if !remoteNameMatcher.MatchString(remoteName) {
 		return errInvalidCharacters
 	}
 	return nil
 }
 
-// Parse deconstructs a remote path into configName and fsPath
+// Return true if c is a valid character for a config parameter
+func isConfigParam(c rune) bool {
+	return ((c >= 'a' && c <= 'z') ||
+		(c >= 'A' && c <= 'Z') ||
+		(c >= '0' && c <= '9') ||
+		c == '_')
+}
+
+// Parsed is returned from Parse with the results of the connection string decomposition
 //
-// If the path is a local path then configName will be returned as "".
+// If Name is "" then it is a local path in Path
 //
-// So "remote:path/to/dir" will return "remote", "path/to/dir"
+// Note that ConfigString + ":" + Path is equal to the input of Parse except that Path may have had
-// and "/path/to/local" will return ("", "/path/to/local")
+// \ converted to /
+type Parsed struct {
+	Name         string           // Just the name of the config: "remote" or ":backend"
+	ConfigString string           // The whole config string: "remote:" or ":backend,value=6:"
+	Path         string           // The file system path, may be empty
+	Config       configmap.Simple // key/value config parsed out of ConfigString may be nil
+}
+
+// Parse deconstructs a path into a Parsed structure
+//
+// If the path is a local path then parsed.Name will be returned as "".
+//
+// So "remote:path/to/dir" will return Parsed{Name:"remote", Path:"path/to/dir"},
+// and "/path/to/local" will return Parsed{Name:"", Path:"/path/to/local"}
 //
 // Note that this will turn \ into / in the fsPath on Windows
 //
-// An error may be returned if the remote name has invalid characters
+// An error may be returned if the remote name has invalid characters or the
-// in it or if the path is empty.
+// parameters are invalid or the path is empty.
-func Parse(path string) (configName, fsPath string, err error) {
+func Parse(path string) (parsed Parsed, err error) {
+	parsed.Path = path
 	if path == "" {
-		return "", "", errCantBeEmpty
+		return parsed, errCantBeEmpty
 	}
-	parts := urlMatcher.FindStringSubmatch(path)
+	// If path has no `:` in, it must be a local path
-	configName, fsPath = "", path
+	if strings.IndexRune(path, ':') < 0 {
-	if parts != nil && !driveletter.IsDriveLetter(parts[1]) {
+		return parsed, nil
-		configName, fsPath = parts[1], parts[2]
+	}
-		err = CheckRemoteName(configName + ":")
+	// States for parser
-		if err != nil {
+	const (
-			return configName, fsPath, errInvalidCharacters
+		stateConfigName = uint8(iota)
+		stateParam
+		stateValue
+		stateQuotedValue
+		stateAfterQuote
+		stateDone
+	)
+	var (
+		state   = stateConfigName // current state of parser
+		i       int               // position in path
+		prev    int               // previous position in path
+		c       rune              // current rune under consideration
+		quote   rune              // kind of quote to end this quoted string
+		param   string            // current parameter value
+		doubled bool              // set if had doubled quotes
+	)
+loop:
+	for i, c = range path {
+		// Example Parse
+		// remote,param=value,param2="qvalue":/path/to/file
+		switch state {
+		// Parses "remote,"
+		case stateConfigName:
+			if i == 0 && c == ':' {
+				continue
+			} else if c == '/' || c == '\\' {
+				// `:` or `,` not before a path separator must be a local path,
+				// except if the path started with `:` in which case it was intended
+				// to be an on the fly remote so return an error.
+				if path[0] == ':' {
+					return parsed, errInvalidCharacters
+				}
+				return parsed, nil
+			} else if c == ':' || c == ',' {
+				parsed.Name = path[:i]
+				err := checkRemoteName(parsed.Name + ":")
+				if err != nil {
+					return parsed, err
+				}
+				prev = i + 1
+				if c == ':' {
+					// If we parsed a drive letter, must be a local path
+					if isDriveLetter(parsed.Name) {
+						parsed.Name = ""
+						return parsed, nil
+					}
+					state = stateDone
+					break loop
+				}
+				state = stateParam
+				parsed.Config = make(configmap.Simple)
+			}
+		// Parses param= and param2=
+		case stateParam:
+			if c == ':' || c == ',' || c == '=' {
+				param = path[prev:i]
+				if len(param) == 0 {
+					return parsed, errEmptyConfigParam
+				}
+				prev = i + 1
+				if c == '=' {
+					state = stateValue
+					break
+				}
+				parsed.Config[param] = "true"
+				if c == ':' {
+					state = stateDone
+					break loop
+				}
+				state = stateParam
+			} else if !isConfigParam(c) {
+				return parsed, errBadConfigParam
+			}
+		// Parses value
+		case stateValue:
+			if c == '\'' || c == '"' {
+				if i == prev {
+					quote = c
+					state = stateQuotedValue
+					prev = i + 1
+					doubled = false
+					break
+				}
+			} else if c == ':' || c == ',' {
+				value := path[prev:i]
+				prev = i + 1
+				parsed.Config[param] = value
+				if c == ':' {
+					state = stateDone
+					break loop
+				}
+				state = stateParam
+			}
+		// Parses "qvalue"
+		case stateQuotedValue:
+			if c == quote {
+				state = stateAfterQuote
+			}
+		// Parses : or , or quote after "qvalue"
+		case stateAfterQuote:
+			if c == ':' || c == ',' {
+				value := path[prev : i-1]
+				// replace any doubled quotes if there were any
+				if doubled {
+					value = strings.Replace(value, string(quote)+string(quote), string(quote), -1)
+				}
+				prev = i + 1
+				parsed.Config[param] = value
+				if c == ':' {
+					state = stateDone
+					break loop
+				} else {
+					state = stateParam
+				}
+			} else if c == quote {
+				// Here is a doubled quote to indicate a literal quote
+				state = stateQuotedValue
+				doubled = true
+			} else {
+				return parsed, errAfterQuote
+			}
 		}
+
 	}
+
+	// Depending on which state we were in when we fell off the
+	// end of the state machine we can return a sensible error.
+	switch state {
+	default:
+		return parsed, errSyntax
+	case stateConfigName:
+		return parsed, errConfigName
+	case stateParam:
+		return parsed, errParam
+	case stateValue:
+		return parsed, errValue
+	case stateQuotedValue:
+		return parsed, errQuotedValue
+	case stateAfterQuote:
+		return parsed, errAfterQuote
+	case stateDone:
+		break
+	}
+
+	parsed.ConfigString = path[:i]
+	parsed.Path = path[i+1:]
+
 	// change native directory separators to / if there are any
-	fsPath = filepath.ToSlash(fsPath)
+	parsed.Path = filepath.ToSlash(parsed.Path)
-	return configName, fsPath, nil
+	return parsed, nil
 }
 
 // Split splits a remote into a parent and a leaf
@@ -90,10 +268,11 @@ func Parse(path string) (configName, fsPath string, err error) {
 // The returned values have the property that parent + leaf == remote
 // (except under Windows where \ will be translated into /)
 func Split(remote string) (parent string, leaf string, err error) {
-	remoteName, remotePath, err := Parse(remote)
+	parsed, err := Parse(remote)
 	if err != nil {
 		return "", "", err
 	}
+	remoteName, remotePath := parsed.ConfigString, parsed.Path
 	if remoteName != "" {
 		remoteName += ":"
 	}
@@ -130,7 +309,8 @@ func JoinRootPath(remote, filePath string) string {
 	if strings.HasPrefix(remote, "//") {
 		return "/" + path.Join(remote, filePath)
 	}
-	remoteName, remotePath, err := Parse(remote)
+	parsed, err := Parse(remote)
+	remoteName, remotePath := parsed.ConfigString, parsed.Path
 	if err != nil {
 		// Couldn't parse so assume it is a path
 		remoteName = ""

fs/fspath/path_test.go

@@ -1,13 +1,23 @@
 package fspath
 
 import (
+	"flag"
 	"fmt"
+	"io/ioutil"
+	"os"
 	"path/filepath"
 	"runtime"
 	"strings"
 	"testing"
 
+	"github.com/rclone/rclone/fs/config/configmap"
+	"github.com/rclone/rclone/fs/driveletter"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+var (
+	makeCorpus = flag.Bool("make-corpus", false, "Set to make the fuzzing corpus")
 )
 
 func TestCheckConfigName(t *testing.T) {
@@ -39,6 +49,7 @@ func TestCheckRemoteName(t *testing.T) {
 		want error
 	}{
 		{":remote:", nil},
+		{":s3:", nil},
 		{"remote:", nil},
 		{"", errInvalidCharacters},
 		{"rem:ote", errInvalidCharacters},
@@ -49,44 +60,267 @@ func TestCheckRemoteName(t *testing.T) {
 		{"[remote:", errInvalidCharacters},
 		{"*:", errInvalidCharacters},
 	} {
-		got := CheckRemoteName(test.in)
+		got := checkRemoteName(test.in)
 		assert.Equal(t, test.want, got, test.in)
 	}
 }
 
 func TestParse(t *testing.T) {
-	for _, test := range []struct {
+	isDriveLetter = func(name string) bool {
-		in, wantConfigName, wantFsPath string
+		return name == "C"
-		wantErr                        error
+	}
+	defer func() {
+		isDriveLetter = driveletter.IsDriveLetter
+	}()
+
+	for testNumber, test := range []struct {
+		in         string
+		wantParsed Parsed
+		wantErr    error
 	}{
-		{"", "", "", errCantBeEmpty},
+		{
-		{":", "", "", errInvalidCharacters},
+			in:      "",
-		{"::", ":", "", errInvalidCharacters},
+			wantErr: errCantBeEmpty,
-		{":/:", "", "/:", errInvalidCharacters},
+		}, {
-		{"/:", "", "/:", nil},
+			in:      ":",
-		{"\\backslash:", "", "\\backslash:", nil},
+			wantErr: errConfigName,
-		{"/slash:", "", "/slash:", nil},
+		}, {
-		{"with\\backslash:", "", "with\\backslash:", nil},
+			in:      "::",
-		{"with/slash:", "", "with/slash:", nil},
+			wantErr: errConfigNameEmpty,
-		{"/path/to/file", "", "/path/to/file", nil},
+		}, {
-		{"/path:/to/file", "", "/path:/to/file", nil},
+			in:      ":/:",
-		{"./path:/to/file", "", "./path:/to/file", nil},
+			wantErr: errInvalidCharacters,
-		{"./:colon.txt", "", "./:colon.txt", nil},
+		}, {
-		{"path/to/file", "", "path/to/file", nil},
+			in: "/:",
-		{"remote:path/to/file", "remote", "path/to/file", nil},
+			wantParsed: Parsed{
-		{"rem*ote:path/to/file", "rem*ote", "path/to/file", errInvalidCharacters},
+				ConfigString: "",
-		{"remote:/path/to/file", "remote", "/path/to/file", nil},
+				Path:         "/:",
-		{"rem.ote:/path/to/file", "rem.ote", "/path/to/file", errInvalidCharacters},
+			},
-		{":backend:/path/to/file", ":backend", "/path/to/file", nil},
+		}, {
-		{":bac*kend:/path/to/file", ":bac*kend", "/path/to/file", errInvalidCharacters},
+			in: "\\backslash:",
+			wantParsed: Parsed{
+				ConfigString: "",
+				Path:         "\\backslash:",
+			},
+		}, {
+			in: "/slash:",
+			wantParsed: Parsed{
+				ConfigString: "",
+				Path:         "/slash:",
+			},
+		}, {
+			in: "with\\backslash:",
+			wantParsed: Parsed{
+				ConfigString: "",
+				Path:         "with\\backslash:",
+			},
+		}, {
+			in: "with/slash:",
+			wantParsed: Parsed{
+				ConfigString: "",
+				Path:         "with/slash:",
+			},
+		}, {
+			in: "/path/to/file",
+			wantParsed: Parsed{
+				ConfigString: "",
+				Path:         "/path/to/file",
+			},
+		}, {
+			in: "/path:/to/file",
+			wantParsed: Parsed{
+				ConfigString: "",
+				Path:         "/path:/to/file",
+			},
+		}, {
+			in: "./path:/to/file",
+			wantParsed: Parsed{
+				ConfigString: "",
+				Path:         "./path:/to/file",
+			},
+		}, {
+			in: "./:colon.txt",
+			wantParsed: Parsed{
+				ConfigString: "",
+				Path:         "./:colon.txt",
+			},
+		}, {
+			in: "path/to/file",
+			wantParsed: Parsed{
+				ConfigString: "",
+				Path:         "path/to/file",
+			},
+		}, {
+			in: "remote:path/to/file",
+			wantParsed: Parsed{
+				ConfigString: "remote",
+				Name:         "remote",
+				Path:         "path/to/file",
+			},
+		}, {
+			in:      "rem*ote:path/to/file",
+			wantErr: errInvalidCharacters,
+		}, {
+			in: "remote:/path/to/file",
+			wantParsed: Parsed{
+				ConfigString: "remote",
+				Name:         "remote",
+				Path:         "/path/to/file",
+			},
+		}, {
+			in:      "rem.ote:/path/to/file",
+			wantErr: errInvalidCharacters,
+		}, {
+			in: ":backend:/path/to/file",
+			wantParsed: Parsed{
+				ConfigString: ":backend",
+				Name:         ":backend",
+				Path:         "/path/to/file",
+			},
+		}, {
+			in:      ":bac*kend:/path/to/file",
+			wantErr: errInvalidCharacters,
+		}, {
+			in: `C:\path\to\file`,
+			wantParsed: Parsed{
+				Name: "",
+				Path: `C:\path\to\file`,
+			},
+		}, {
+			in: `remote:\path\to\file`,
+			wantParsed: Parsed{
+				Name:         "remote",
+				ConfigString: "remote",
+				Path:         `\path\to\file`,
+			},
+		}, {
+			in: `D:/path/to/file`,
+			wantParsed: Parsed{
+				Name:         "D",
+				ConfigString: "D",
+				Path:         `/path/to/file`,
+			},
+		}, {
+			in: `:backend,param1:/path/to/file`,
+			wantParsed: Parsed{
+				ConfigString: `:backend,param1`,
+				Name:         ":backend",
+				Path:         "/path/to/file",
+				Config: configmap.Simple{
+					"param1": "true",
+				},
+			},
+		}, {
+			in: `:backend,param1=value:/path/to/file`,
+			wantParsed: Parsed{
+				ConfigString: `:backend,param1=value`,
+				Name:         ":backend",
+				Path:         "/path/to/file",
+				Config: configmap.Simple{
+					"param1": "value",
+				},
+			},
+		}, {
+			in: `:backend,param1=value1,param2,param3=value3:/path/to/file`,
+			wantParsed: Parsed{
+				ConfigString: `:backend,param1=value1,param2,param3=value3`,
+				Name:         ":backend",
+				Path:         "/path/to/file",
+				Config: configmap.Simple{
+					"param1": "value1",
+					"param2": "true",
+					"param3": "value3",
+				},
+			},
+		}, {
+			in: `:backend,param1=value1,param2="value2",param3='value3':/path/to/file`,
+			wantParsed: Parsed{
+				ConfigString: `:backend,param1=value1,param2="value2",param3='value3'`,
+				Name:         ":backend",
+				Path:         "/path/to/file",
+				Config: configmap.Simple{
+					"param1": "value1",
+					"param2": "value2",
+					"param3": "value3",
+				},
+			},
+		}, {
+			in:      `:backend,param-1=value:/path/to/file`,
+			wantErr: errBadConfigParam,
+		}, {
+			in:      `:backend,param1="value"x:/path/to/file`,
+			wantErr: errAfterQuote,
+		}, {
+			in:      `:backend,`,
+			wantErr: errParam,
+		}, {
+			in:      `:backend,param=value`,
+			wantErr: errValue,
+		}, {
+			in:      `:backend,param="value'`,
+			wantErr: errQuotedValue,
+		}, {
+			in:      `:backend,param1="value"`,
+			wantErr: errAfterQuote,
+		}, {
+			in:      `:backend,=value:`,
+			wantErr: errEmptyConfigParam,
+		}, {
+			in:      `:backend,:`,
+			wantErr: errEmptyConfigParam,
+		}, {
+			in:      `:backend,,:`,
+			wantErr: errEmptyConfigParam,
+		}, {
+			in: `:backend,param=:path`,
+			wantParsed: Parsed{
+				ConfigString: `:backend,param=`,
+				Name:         ":backend",
+				Path:         "path",
+				Config: configmap.Simple{
+					"param": "",
+				},
+			},
+		}, {
+			in: `:backend,param="with""quote":path`,
+			wantParsed: Parsed{
+				ConfigString: `:backend,param="with""quote"`,
+				Name:         ":backend",
+				Path:         "path",
+				Config: configmap.Simple{
+					"param": `with"quote`,
+				},
+			},
+		}, {
+			in: `:backend,param='''''':`,
+			wantParsed: Parsed{
+				ConfigString: `:backend,param=''''''`,
+				Name:         ":backend",
+				Path:         "",
+				Config: configmap.Simple{
+					"param": `''`,
+				},
+			},
+		}, {
+			in:      `:backend,param=''bad'':`,
+			wantErr: errAfterQuote,
+		},
 	} {
-		gotConfigName, gotFsPath, gotErr := Parse(test.in)
+		gotParsed, gotErr := Parse(test.in)
-		if runtime.GOOS == "windows" {
+		// For non-local paths we convert \ into / on Windows
-			test.wantFsPath = strings.Replace(test.wantFsPath, `\`, `/`, -1)
+		if runtime.GOOS == "windows" && test.wantParsed.Name != "" {
+			test.wantParsed.Path = strings.Replace(test.wantParsed.Path, `\`, `/`, -1)
 		}
-		assert.Equal(t, test.wantErr, gotErr)
+		assert.Equal(t, test.wantErr, gotErr, test.in)
-		assert.Equal(t, test.wantConfigName, gotConfigName)
+		if test.wantErr == nil {
-		assert.Equal(t, test.wantFsPath, gotFsPath)
+			assert.Equal(t, test.wantParsed, gotParsed, test.in)
+		}
+		if *makeCorpus {
+			// write the test corpus for fuzzing
+			require.NoError(t, os.MkdirAll("corpus", 0777))
+			require.NoError(t, ioutil.WriteFile(fmt.Sprintf("corpus/%02d", testNumber), []byte(test.in), 0666))
+		}
+
 	}
 }
 

fstest/fstests/fstests.go

@@ -1474,8 +1474,9 @@ func Run(t *testing.T, opt *Opt) {
 					t.Skip("Can't list from root on this remote")
 				}
 
-				configName, configLeaf, err := fspath.Parse(subRemoteName)
+				parsed, err := fspath.Parse(subRemoteName)
 				require.NoError(t, err)
+				configName, configLeaf := parsed.ConfigString, parsed.Path
 				if configName == "" {
 					configName, configLeaf = path.Split(subRemoteName)
 				} else {

fstest/testserver/testserver.go

@@ -122,11 +122,11 @@ func Start(remoteName string) (fn func(), err error) {
 		// don't start the local backend
 		return func() {}, nil
 	}
-	var name string
+	parsed, err := fspath.Parse(remoteName)
-	name, _, err = fspath.Parse(remoteName)
 	if err != nil {
 		return nil, err
 	}
+	name := parsed.ConfigString
 	if name == "" {
 		// don't start the local backend
 		return func() {}, nil