Initial commit

error.go

@@ -0,0 +1,103 @@
+package camfish
+
+import "fmt"
+import "strings"
+
+// Error enumerates common errors in this package.
+type Error string; const (
+	ErrNotFound                Error = "not found"
+	ErrNotRunning              Error = "not running"
+	ErrProcessKilled           Error = "process killed"
+	ErrExtraneousValues        Error = "extraneous value(s)"
+	ErrSectionHeadingMalformed Error = "section heading malformed"
+	ErrPairMalformed           Error = "key/value pair malformed"
+	ErrKeyEmpty                Error = "key empty"
+)
+
+// Error implements the error interface.
+func (err Error) Error() string {
+	return string(err)
+}
+
+// ConfigError pairs an error with a location in a config file.
+type ConfigError struct {
+	File   string
+	Key    string
+	Line   int
+	Column int
+	Err    error
+}
+
+// Error implements the error interface.
+func (err ConfigError) Error() string  {
+	out := strings.Builder { }
+	if err.File != "" {
+		out.WriteString(err.File)
+	}
+	if err.Key != "" {
+		fmt.Fprintf(&out, "[%s]", err.Key)
+	}
+	switch {
+	case err.Line != 0 && err.Column != 0:
+		if out.Len() > 0 { out.WriteRune(':') }
+		fmt.Fprintf(&out, "%d:%d", err.Line, err.Column)
+	case err.Line != 0:
+		if out.Len() > 0 { out.WriteRune(':') }
+		fmt.Fprintf(&out, "%d", err.Line)
+	}
+	if out.Len() > 0 { out.WriteString(": ") }
+	if err.Err == nil {
+		out.WriteString("configuration error")
+	} else {
+		fmt.Fprint(&out, err.Err)
+	}
+	return out.String()
+}
+
+// Unwrap returns err.Err.
+func (err ConfigError) Unwrap() error {
+	return err.Err
+}
+
+// NewConfigError creates a new config error with the given key and config. It
+// will attempt to fill in as many details as possible with the information
+// given. If the config has a method with an identical name and signature to
+// this function, it will be called and its value will be returned. Otherwise,
+// an error is returned containing only the provided information.
+func NewConfigError(config Config, key string, index int, wrapped error) ConfigError {
+	type configErrorFactory interface {
+		NewConfigError(string, int, error) ConfigError
+	}
+	if config, ok := config.(configErrorFactory); ok {
+		return config.NewConfigError(key, index, wrapped)
+	}
+	return ConfigError {
+		Key: key,
+		Err: wrapped,
+	}
+}
+
+// FlagError pairs a flag with a long flag name.
+type FlagError struct {
+	Long string
+	Err  error
+}
+
+// Error implements the error interface.
+func (err FlagError) Error() string {
+	output := err.Long
+	if output != "" {
+		output = fmt.Sprintf("--%s: ", output)
+	}
+	if err.Err == nil {
+		output += "argument parsing error"
+	} else {
+		output += err.Unwrap().Error()
+	}
+	return output
+}
+
+// Unwrap returns err.Err
+func (err FlagError) Unwrap() error {
+	return err.Err
+}