HTML escape and unescape normalizer. Fixes #104

README.md

@@ -98,6 +98,8 @@ This package currently provides the following checkers:
 
 This package currently provides the following normalizers. They can be mixed with the checkers when defining the validation steps for user data.
 
+- [html_escape](doc/normalizers/html_escape.md) applies HTML escaping to special characters.
+- [html_unescape](doc//normalizers/html_unescape.md) applies HTML unescaping to special characters.
 - [lower](doc/normalizers/lower.md) maps all Unicode letters in the given value to their lower case.
 - [upper](doc/normalizers/upper.md) maps all Unicode letters in the given value to their upper case.
 - [title](doc/normalizers/title.md) maps the first letter of each word to their upper case.

checker.go

@@ -37,33 +37,35 @@ const ResultValid Result = "VALID"
 
 // makers provides mapping to maker function for the checkers.
 var makers = map[string]MakeFunc{
-	CheckerAlphanumeric: makeAlphanumeric,
-	CheckerASCII:        makeASCII,
-	CheckerCreditCard:   makeCreditCard,
-	CheckerCidr:         makeCidr,
-	CheckerDigits:       makeDigits,
-	CheckerEmail:        makeEmail,
-	CheckerFqdn:         makeFqdn,
-	CheckerIP:           makeIP,
-	CheckerIPV4:         makeIPV4,
-	CheckerIPV6:         makeIPV6,
-	CheckerISBN:         makeISBN,
-	CheckerLuhn:         makeLuhn,
-	CheckerMac:          makeMac,
-	CheckerMax:          makeMax,
-	CheckerMaxLength:    makeMaxLength,
-	CheckerMin:          makeMin,
-	CheckerMinLength:    makeMinLength,
-	CheckerRegexp:       makeRegexp,
-	CheckerRequired:     makeRequired,
-	CheckerSame:         makeSame,
-	CheckerURL:          makeURL,
-	NormalizerLower:     makeLower,
-	NormalizerUpper:     makeUpper,
-	NormalizerTitle:     makeTitle,
-	NormalizerTrim:      makeTrim,
-	NormalizerTrimLeft:  makeTrimLeft,
-	NormalizerTrimRight: makeTrimRight,
+	CheckerAlphanumeric:    makeAlphanumeric,
+	CheckerASCII:           makeASCII,
+	CheckerCreditCard:      makeCreditCard,
+	CheckerCidr:            makeCidr,
+	CheckerDigits:          makeDigits,
+	CheckerEmail:           makeEmail,
+	CheckerFqdn:            makeFqdn,
+	CheckerIP:              makeIP,
+	CheckerIPV4:            makeIPV4,
+	CheckerIPV6:            makeIPV6,
+	CheckerISBN:            makeISBN,
+	CheckerLuhn:            makeLuhn,
+	CheckerMac:             makeMac,
+	CheckerMax:             makeMax,
+	CheckerMaxLength:       makeMaxLength,
+	CheckerMin:             makeMin,
+	CheckerMinLength:       makeMinLength,
+	CheckerRegexp:          makeRegexp,
+	CheckerRequired:        makeRequired,
+	CheckerSame:            makeSame,
+	CheckerURL:             makeURL,
+	NormalizerHTMLEscape:   makeHTMLEscape,
+	NormalizerHTMLUnescape: makeHTMLUnescape,
+	NormalizerLower:        makeLower,
+	NormalizerUpper:        makeUpper,
+	NormalizerTitle:        makeTitle,
+	NormalizerTrim:         makeTrim,
+	NormalizerTrimLeft:     makeTrimLeft,
+	NormalizerTrimRight:    makeTrimRight,
 }
 
 // Register registers the given checker name and the maker function.

doc/normalizers/html_escape.md

@@ -0,0 +1,19 @@
+# HTML Escape Normalizer
+
+The `html-escape` normalizer uses [html.EscapeString](https://pkg.go.dev/html#EscapeString) to escape special characters like "<" to become "&lt;". It escapes only five such characters: <, >, &, ' and ".
+
+```golang
+type Comment struct {
+  Body string `checkers:"html-escape"`
+}
+
+comment := &Comment{
+  Body: "<tag> \"Checker\" & 'Library' </tag>",
+}
+
+checker.Check(comment)
+
+// Outputs: 
+// &lt;tag&gt; &#34;Checker&#34; &amp; &#39;Library&#39; &lt;/tag&gt;
+fmt.Println(comment.Body)
+```

doc/normalizers/html_unescape.md

@@ -0,0 +1,22 @@
+# HTML Unescape Normalizer
+
+The `html-unescape` normalizer uses [html.UnescapeString](https://pkg.go.dev/html#UnescapeString) to unescape entities like "&lt;" to become "<". It unescapes a larger range of entities than EscapeString escapes. For example, "&aacute;" unescapes to "á", as does "&#225;" and "&#xE1;".
+
+```golang
+type Comment struct {
+  Body string `checkers:"html-unescape"`
+}
+
+comment := &Comment{
+  Body: "&lt;tag&gt; &#34;Checker&#34; &amp; &#39;Library&#39; &lt;/tag&gt;",
+}
+
+_, valid := checker.Check(comment)
+if !valid {
+  t.Fail()
+}
+
+// Outputs:
+// <tag> \"Checker\" & 'Library' </tag>
+fmt.Println(comment.Body)
+```

html_escape.go

@@ -0,0 +1,26 @@
+package checker
+
+import (
+	"html"
+	"reflect"
+)
+
+// NormalizerHTMLEscape is the name of the normalizer.
+const NormalizerHTMLEscape = "html-escape"
+
+// makeHTMLEscape makes a normalizer function for the HTML escape normalizer.
+func makeHTMLEscape(_ string) CheckFunc {
+	return normalizeHTMLEscape
+}
+
+// normalizeHTMLEscape applies HTML escaping to special characters.
+// Uses html.EscapeString for the actual escape operation.
+func normalizeHTMLEscape(value, _ reflect.Value) Result {
+	if value.Kind() != reflect.String {
+		panic("string expected")
+	}
+
+	value.SetString(html.EscapeString(value.String()))
+
+	return ResultValid
+}

html_escape_test.go

@@ -0,0 +1,38 @@
+package checker_test
+
+import (
+	"testing"
+
+	"github.com/cinar/checker"
+)
+
+func TestNormalizeHTMLEscapeNonString(t *testing.T) {
+	defer checker.FailIfNoPanic(t)
+
+	type Comment struct {
+		Body int `checkers:"html-escape"`
+	}
+
+	comment := &Comment{}
+
+	checker.Check(comment)
+}
+
+func TestNormalizeHTMLEscape(t *testing.T) {
+	type Comment struct {
+		Body string `checkers:"html-escape"`
+	}
+
+	comment := &Comment{
+		Body: "<tag> \"Checker\" & 'Library' </tag>",
+	}
+
+	_, valid := checker.Check(comment)
+	if !valid {
+		t.Fail()
+	}
+
+	if comment.Body != "&lt;tag&gt; &#34;Checker&#34; &amp; &#39;Library&#39; &lt;/tag&gt;" {
+		t.Fail()
+	}
+}

html_unescape.go

@@ -0,0 +1,26 @@
+package checker
+
+import (
+	"html"
+	"reflect"
+)
+
+// NormalizerHTMLUnescape is the name of the normalizer.
+const NormalizerHTMLUnescape = "html-unescape"
+
+// makeHTMLUnescape makes a normalizer function for the HTML unscape normalizer.
+func makeHTMLUnescape(_ string) CheckFunc {
+	return normalizeHTMLUnescape
+}
+
+// normalizeHTMLUnescape applies HTML unescaping to special characters.
+// Uses html.UnescapeString for the actual unescape operation.
+func normalizeHTMLUnescape(value, _ reflect.Value) Result {
+	if value.Kind() != reflect.String {
+		panic("string expected")
+	}
+
+	value.SetString(html.UnescapeString(value.String()))
+
+	return ResultValid
+}

html_unescape_test.go

@@ -0,0 +1,38 @@
+package checker_test
+
+import (
+	"testing"
+
+	"github.com/cinar/checker"
+)
+
+func TestNormalizeHTMLUnescapeNonString(t *testing.T) {
+	defer checker.FailIfNoPanic(t)
+
+	type Comment struct {
+		Body int `checkers:"html-unescape"`
+	}
+
+	comment := &Comment{}
+
+	checker.Check(comment)
+}
+
+func TestNormalizeHTMLUnescape(t *testing.T) {
+	type Comment struct {
+		Body string `checkers:"html-unescape"`
+	}
+
+	comment := &Comment{
+		Body: "<tag> "Checker" & 'Library' </tag>",
+	}
+
+	_, valid := checker.Check(comment)
+	if !valid {
+		t.Fail()
+	}
+
+	if comment.Body != "<tag> \"Checker\" & 'Library' </tag>" {
+		t.Fail()
+	}
+}