Merge pull request #44 from gdholtslander/error-matching

Add defined errors to the package

Author: anaskhan96

CHANGELOG.md

@@ -1,4 +1,15 @@
-## v1.1
+## v1.2.0
+
+### Added
+
+- ErrorDetails to the Root object. This will contain the templated error messages that used to be returned by Error
+
+## Changed
+
+- Error will now be one of a standard set of errors defined by the package. Details about the error message have been moved
+to the ErrorDetails property of Root.
+
+## v1.1.0
 
 ### Added
 

examples/errors/errors.go

@@ -0,0 +1,33 @@
+// Errors happen. This example shows how to detect and handle some of them.
+
+package main
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/anaskhan96/soup"
+)
+
+func main() {
+	_, err := soup.Get("this url isn't real!")
+	if err != nil && err.(soup.Error).Type == soup.ErrInGetRequest {
+		// Handle as required!
+	}
+
+	url := fmt.Sprintf("https://xkcd.com/50")
+	xkcd, err := soup.Get(url)
+	if err != nil {
+		// Handle it
+	}
+	xkcdSoup := soup.HTMLParse(xkcd)
+	links := xkcdSoup.Find("div", "id", "linkz")
+	if links.Error != nil && links.Error.(soup.Error).Type == soup.ErrElementNotFound {
+		log.Printf("Element not found: %v", links.Error)
+	}
+	// These error types were introduced in version 1.2.0, but just checking for err still works:
+	links = xkcdSoup.Find("div", "id", "links2")
+	if links.Error != nil {
+		log.Printf("Something happened: %s", links.Error)
+	}
+}

soup.go

@@ -6,7 +6,7 @@ package soup
 
 import (
 	"bytes"
-	"errors"
+	"fmt"
 	"io/ioutil"
 	"net/http"
 	"regexp"
@@ -15,20 +15,67 @@ import (
 	"golang.org/x/net/html"
 )
 
-// Root is a structure containing a pointer to an html node, the node value, and an error variable to return an error if occurred
+// ErrorType defines types of errors that are possible from soup
+type ErrorType int
+
+const (
+	// ErrUnableToParse will be returned when the HTML could not be parsed
+	ErrUnableToParse ErrorType = iota
+	// ErrElementNotFound will be returned when element was not found
+	ErrElementNotFound
+	// ErrNoNextSibling will be returned when no next sibling can be found
+	ErrNoNextSibling
+	// ErrNoPreviousSibling will be returned when no previous sibling can be found
+	ErrNoPreviousSibling
+	// ErrNoNextElementSibling will be returned when no next element sibling can be found
+	ErrNoNextElementSibling
+	// ErrNoPreviousElementSibling will be returned when no previous element sibling can be found
+	ErrNoPreviousElementSibling
+	// ErrCreatingGetRequest will be returned when the get request couldn't be created
+	ErrCreatingGetRequest
+	// ErrInGetRequest will be returned when there was an error during the get request
+	ErrInGetRequest
+	// ErrReadingResponse will be returned if there was an error reading the response to our get request
+	ErrReadingResponse
+)
+
+// Error allows easier introspection on the type of error returned.
+// If you know you have a Error, you can compare the Type to one of the exported types
+// from this package to see what kind of error it is, then further inspect the Error() method
+// to see if it has more specific details for you, like in the case of a ErrElementNotFound
+// type of error.
+type Error struct {
+	Type ErrorType
+	msg  string
+}
+
+func (se Error) Error() string {
+	return se.msg
+}
+
+func newError(t ErrorType, msg string) Error {
+	return Error{Type: t, msg: msg}
+}
+
+// Root is a structure containing a pointer to an html node, the node value, and an error variable to return an error if one occurred
 type Root struct {
 	Pointer   *html.Node
 	NodeValue string
 	Error     error
 }
 
-var debug = false
+// Init a new HTTP client for use when the client doesn't want to use their own.
+var (
+	defaultClient = &http.Client{}
 
-// Headers contains all HTTP headers to send
-var Headers = make(map[string]string)
+	debug = false
 
-// Cookies contains all HTTP cookies to send
-var Cookies = make(map[string]string)
+	// Headers contains all HTTP headers to send
+	Headers = make(map[string]string)
+
+	// Cookies contains all HTTP cookies to send
+	Cookies = make(map[string]string)
+)
 
 // SetDebug sets the debug status
 // Setting this to true causes the panics to be thrown and logged onto the console.
@@ -42,6 +89,7 @@ func Header(n string, v string) {
 	Headers[n] = v
 }
 
+// Cookie sets a cookie for http requests
 func Cookie(n string, v string) {
 	Cookies[n] = v
 }
@@ -53,7 +101,7 @@ func GetWithClient(url string, client *http.Client) (string, error) {
 		if debug {
 			panic("Couldn't perform GET request to " + url)
 		}
-		return "", errors.New("couldn't perform GET request to " + url)
+		return "", newError(ErrCreatingGetRequest, "error creating get request to "+url)
 	}
 	// Set headers
 	for hName, hValue := range Headers {
@@ -72,24 +120,22 @@ func GetWithClient(url string, client *http.Client) (string, error) {
 		if debug {
 			panic("Couldn't perform GET request to " + url)
 		}
-		return "", errors.New("couldn't perform GET request to " + url)
+		return "", newError(ErrInGetRequest, "couldn't perform GET request to "+url)
 	}
 	defer resp.Body.Close()
 	bytes, err := ioutil.ReadAll(resp.Body)
 	if err != nil {
 		if debug {
 			panic("Unable to read the response body")
 		}
-		return "", errors.New("unable to read the response body")
+		return "", newError(ErrReadingResponse, "unable to read the response body")
 	}
 	return string(bytes), nil
 }
 
 // Get returns the HTML returned by the url in string using the default HTTP client
 func Get(url string) (string, error) {
-	// Init a new HTTP client
-	client := &http.Client{}
-	return GetWithClient(url, client)
+	return GetWithClient(url, defaultClient)
 }
 
 // HTMLParse parses the HTML returning a start pointer to the DOM
@@ -99,7 +145,7 @@ func HTMLParse(s string) Root {
 		if debug {
 			panic("Unable to parse the HTML")
 		}
-		return Root{nil, "", errors.New("unable to parse the HTML")}
+		return Root{Error: newError(ErrUnableToParse, "unable to parse the HTML")}
 	}
 	for r.Type != html.ElementNode {
 		switch r.Type {
@@ -111,7 +157,7 @@ func HTMLParse(s string) Root {
 			r = r.NextSibling
 		}
 	}
-	return Root{r, r.Data, nil}
+	return Root{Pointer: r, NodeValue: r.Data}
 }
 
 // Find finds the first occurrence of the given tag name,
@@ -123,9 +169,9 @@ func (r Root) Find(args ...string) Root {
 		if debug {
 			panic("Element `" + args[0] + "` with attributes `" + strings.Join(args[1:], " ") + "` not found")
 		}
-		return Root{nil, "", errors.New("element `" + args[0] + "` with attributes `" + strings.Join(args[1:], " ") + "` not found")}
+		return Root{Error: newError(ErrElementNotFound, fmt.Sprintf("element `%s` with attributes `%s` not found", args[0], strings.Join(args[1:], " ")))}
 	}
-	return Root{temp, temp.Data, nil}
+	return Root{Pointer: temp, NodeValue: temp.Data}
 }
 
 // FindAll finds all occurrences of the given tag name,
@@ -142,7 +188,7 @@ func (r Root) FindAll(args ...string) []Root {
 	}
 	pointers := make([]Root, 0, len(temp))
 	for i := 0; i < len(temp); i++ {
-		pointers = append(pointers, Root{temp[i], temp[i].Data, nil})
+		pointers = append(pointers, Root{Pointer: temp[i], NodeValue: temp[i].Data})
 	}
 	return pointers
 }
@@ -155,9 +201,9 @@ func (r Root) FindStrict(args ...string) Root {
 		if debug {
 			panic("Element `" + args[0] + "` with attributes `" + strings.Join(args[1:], " ") + "` not found")
 		}
-		return Root{nil, "", errors.New("element `" + args[0] + "` with attributes `" + strings.Join(args[1:], " ") + "` not found")}
+		return Root{nil, "", newError(ErrElementNotFound, fmt.Sprintf("element `%s` with attributes `%s` not found", args[0], strings.Join(args[1:], " ")))}
 	}
-	return Root{temp, temp.Data, nil}
+	return Root{Pointer: temp, NodeValue: temp.Data}
 }
 
 // FindAllStrict finds all occurrences of the given tag name
@@ -172,7 +218,7 @@ func (r Root) FindAllStrict(args ...string) []Root {
 	}
 	pointers := make([]Root, 0, len(temp))
 	for i := 0; i < len(temp); i++ {
-		pointers = append(pointers, Root{temp[i], temp[i].Data, nil})
+		pointers = append(pointers, Root{Pointer: temp[i], NodeValue: temp[i].Data})
 	}
 	return pointers
 }
@@ -185,9 +231,9 @@ func (r Root) FindNextSibling() Root {
 		if debug {
 			panic("No next sibling found")
 		}
-		return Root{nil, "", errors.New("no next sibling found")}
+		return Root{Error: newError(ErrNoNextSibling, "no next sibling found")}
 	}
-	return Root{nextSibling, nextSibling.Data, nil}
+	return Root{Pointer: nextSibling, NodeValue: nextSibling.Data}
 }
 
 // FindPrevSibling finds the previous sibling of the pointer in the DOM
@@ -198,9 +244,10 @@ func (r Root) FindPrevSibling() Root {
 		if debug {
 			panic("No previous sibling found")
 		}
-		return Root{nil, "", errors.New("no previous sibling found")}
+
+		return Root{Error: newError(ErrNoPreviousSibling, "no previous sibling found")}
 	}
-	return Root{prevSibling, prevSibling.Data, nil}
+	return Root{Pointer: prevSibling, NodeValue: prevSibling.Data}
 }
 
 // FindNextElementSibling finds the next element sibling of the pointer in the DOM
@@ -211,12 +258,12 @@ func (r Root) FindNextElementSibling() Root {
 		if debug {
 			panic("No next element sibling found")
 		}
-		return Root{nil, "", errors.New("no next element sibling found")}
+		return Root{Error: newError(ErrNoNextElementSibling, "no next element sibling found")}
 	}
 	if nextSibling.Type == html.ElementNode {
-		return Root{nextSibling, nextSibling.Data, nil}
+		return Root{Pointer: nextSibling, NodeValue: nextSibling.Data}
 	}
-	p := Root{nextSibling, nextSibling.Data, nil}
+	p := Root{Pointer: nextSibling, NodeValue: nextSibling.Data}
 	return p.FindNextElementSibling()
 }
 
@@ -228,12 +275,12 @@ func (r Root) FindPrevElementSibling() Root {
 		if debug {
 			panic("No previous element sibling found")
 		}
-		return Root{nil, "", errors.New("no previous element sibling found")}
+		return Root{Error: newError(ErrNoPreviousElementSibling, "no previous element sibling found")}
 	}
 	if prevSibling.Type == html.ElementNode {
-		return Root{prevSibling, prevSibling.Data, nil}
+		return Root{Pointer: prevSibling, NodeValue: prevSibling.Data}
 	}
-	p := Root{prevSibling, prevSibling.Data, nil}
+	p := Root{Pointer: prevSibling, NodeValue: prevSibling.Data}
 	return p.FindPrevElementSibling()
 }
 
@@ -242,7 +289,7 @@ func (r Root) Children() []Root {
 	child := r.Pointer.FirstChild
 	var children []Root
 	for child != nil {
-		children = append(children, Root{child, child.Data, nil})
+		children = append(children, Root{Pointer: child, NodeValue: child.Data})
 		child = child.NextSibling
 	}
 	return children

soup_test.go

@@ -5,6 +5,8 @@ import (
 	"strconv"
 	"strings"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
 )
 
 const testHTML = `
@@ -205,10 +207,24 @@ func TestFullText(t *testing.T) {
 }
 
 func TestFullTextEmpty(t *testing.T) {
-    // <div id="5"><h1><span></span></h1></div>
-    h1 := doc.Find("div", "id", "5").Find("h1")
+	// <div id="5"><h1><span></span></h1></div>
+	h1 := doc.Find("div", "id", "5").Find("h1")
 
-    if h1.FullText() != "" {
+	if h1.FullText() != "" {
 		t.Errorf("Wrong text: %s", h1.FullText())
 	}
 }
+
+func TestNewErrorReturnsInspectableError(t *testing.T) {
+	err := newError(ErrElementNotFound, "element not found")
+	assert.NotNil(t, err)
+	assert.Equal(t, ErrElementNotFound, err.Type)
+	assert.Equal(t, "element not found", err.Error())
+}
+
+func TestFindReturnsInspectableError(t *testing.T) {
+	r := doc.Find("bogus", "thing")
+	assert.IsType(t, Error{}, r.Error)
+	assert.Equal(t, "element `bogus` with attributes `thing` not found", r.Error.Error())
+	assert.Equal(t, ErrElementNotFound, r.Error.(Error).Type)
+}