From e051c4a982f9d7703064bdeaea65ecb0d56327bd Mon Sep 17 00:00:00 2001
From: Kenneth Shaw <kenneth.shaw@knq.io>
Date: Fri, 13 Jul 2018 09:28:45 +0700
Subject: [PATCH] Removing errors dependency in client and runner packages

---
 client/gen.go        |  2 --
 client/targettype.go |  2 --
 runner/runner.go     | 37 +++++++++++++++++++++++++++++++------
 3 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/client/gen.go b/client/gen.go
index f473f48..35ed799 100644
--- a/client/gen.go
+++ b/client/gen.go
@@ -93,7 +93,6 @@ const (
 // Code generated by gen.go. DO NOT EDIT.
 
 import (
-	// "errors"
 	easyjson "github.com/mailru/easyjson"
 	jlexer "github.com/mailru/easyjson/jlexer"
 	jwriter "github.com/mailru/easyjson/jwriter"
@@ -129,7 +128,6 @@ func (tt *TargetType) UnmarshalEasyJSON(in *jlexer.Lexer) {
 %s
 
 	default:
-		// in.AddError(errors.New("unknown TargetType"))
 		*tt = z
 	}
 }
diff --git a/client/targettype.go b/client/targettype.go
index 073eecc..50e918e 100644
--- a/client/targettype.go
+++ b/client/targettype.go
@@ -3,7 +3,6 @@ package client
 // Code generated by gen.go. DO NOT EDIT.
 
 import (
-	// "errors"
 	easyjson "github.com/mailru/easyjson"
 	jlexer "github.com/mailru/easyjson/jlexer"
 	jwriter "github.com/mailru/easyjson/jwriter"
@@ -70,7 +69,6 @@ func (tt *TargetType) UnmarshalEasyJSON(in *jlexer.Lexer) {
 		*tt = Worker
 
 	default:
-		// in.AddError(errors.New("unknown TargetType"))
 		*tt = z
 	}
 }
diff --git a/runner/runner.go b/runner/runner.go
index b21afbe..c2623c2 100644
--- a/runner/runner.go
+++ b/runner/runner.go
@@ -3,7 +3,6 @@ package runner
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"io/ioutil"
 	"net/url"
@@ -17,6 +16,32 @@ import (
 	"github.com/chromedp/chromedp/client"
 )
 
+// Error is a runner error.
+type Error string
+
+// Error satisfies the error interface.
+func (err Error) Error() string {
+	return string(err)
+}
+
+// Error values.
+const (
+	// ErrAlreadyStarted is the already started error.
+	ErrAlreadyStarted Error = "already started"
+
+	// ErrAlreadyWaiting is the already waiting error.
+	ErrAlreadyWaiting Error = "already waiting"
+
+	// ErrInvalidCmdOpts is the invalid cmd-opts error.
+	ErrInvalidCmdOpts Error = "invalid cmd-opts"
+
+	// ErrInvalidProcessOpts is the invalid process-opts error.
+	ErrInvalidProcessOpts Error = "invalid process-opts"
+
+	// ErrExecPathNotSet is the exec-path not set set error.
+	ErrExecPathNotSet Error = "exec-path command line option not set, or chrome executable not found in PATH"
+)
+
 const (
 	// DefaultUserDataDirPrefix is the default user data directory prefix.
 	DefaultUserDataDirPrefix = "chromedp-runner.%d."
@@ -128,7 +153,7 @@ func (r *Runner) Start(ctxt context.Context) error {
 	r.rw.RUnlock()
 
 	if cmd != nil {
-		return errors.New("already started")
+		return ErrAlreadyStarted
 	}
 
 	// setup context
@@ -150,7 +175,7 @@ func (r *Runner) Start(ctxt context.Context) error {
 	// ensure exec-path set
 	execPath, ok := r.opts["exec-path"]
 	if !ok {
-		return errors.New("exec-path command line option not set, or chrome executable not found in $PATH")
+		return ErrExecPathNotSet
 	}
 
 	// create cmd
@@ -235,7 +260,7 @@ func (r *Runner) Wait() error {
 	r.rw.RUnlock()
 
 	if waiting {
-		return errors.New("already waiting")
+		return ErrAlreadyWaiting
 	}
 
 	r.rw.Lock()
@@ -427,7 +452,7 @@ func CmdOpt(o func(*exec.Cmd) error) CommandLineOption {
 		if e, ok := m["cmd-opts"]; ok {
 			opts, ok = e.([]func(*exec.Cmd) error)
 			if !ok {
-				return errors.New("cmd-opts is in invalid state")
+				return ErrInvalidCmdOpts
 			}
 		}
 
@@ -446,7 +471,7 @@ func ProcessOpt(o func(*os.Process) error) CommandLineOption {
 		if e, ok := m["process-opts"]; ok {
 			opts, ok = e.([]func(*os.Process) error)
 			if !ok {
-				return errors.New("process-opts is in invalid state")
+				return ErrInvalidProcessOpts
 			}
 		}