Implement EPUB/WebPub exemptions (#184)

pkg/manifest/a11y.go

@@ -19,6 +19,7 @@ type A11y struct {
 	AccessModesSufficient [][]A11yPrimaryAccessMode `json:"accessModeSufficient,omitempty"` //  A list of single or combined accessModes that are sufficient to understand all the intellectual content of a resource.
 	Features              []A11yFeature             `json:"feature,omitempty"`              // Content features of the resource, such as accessible media, alternatives and supported enhancements for accessibility.
 	Hazards               []A11yHazard              `json:"hazard,omitempty"`               // A characteristic of the described resource that is physiologically dangerous to some users.
+	Exemptions            []A11yExemption           `json:"exemption,omitempty"`            // Justifications for non-conformance based on exemptions in a given jurisdiction.
 }
 
 // NewA11y creates a new empty A11y.
@@ -29,6 +30,7 @@ func NewA11y() A11y {
 		AccessModesSufficient: [][]A11yPrimaryAccessMode{},
 		Features:              []A11yFeature{},
 		Hazards:               []A11yHazard{},
+		Exemptions:            []A11yExemption{},
 	}
 }
 
@@ -130,6 +132,12 @@ func A11yFromJSON(rawJSON map[string]interface{}) (*A11y, error) {
 	}
 	a.Hazards = A11yHazardsFromStrings(hazards)
 
+	examptions, err := parseSliceOrString(rawJSON["exemption"], true)
+	if err != nil {
+		return nil, errors.Wrap(err, "failed unmarshalling 'exemption'")
+	}
+	a.Exemptions = A11yExemptionsFromStrings(examptions)
+
 	return a, nil
 }
 
@@ -433,6 +441,21 @@ func A11yHazardsFromStrings(strings []string) []A11yHazard {
 	})
 }
 
+// A11yExemption is a justification for non-conformance based on an exemption in a given jurisdiction.
+type A11yExemption string
+
+const (
+	A11yExemptionEAASisproportionateBurden A11yExemption = "eaa-disproportionate-burden"
+	A11yExemptionEAAFundamentalAlteration  A11yExemption = "eaa-fundamental-alteration"
+	A11yExemptionEAAMicroenterprise        A11yExemption = "eaa-microenterprise"
+)
+
+func A11yExemptionsFromStrings(strings []string) []A11yExemption {
+	return fromStrings(strings, func(str string) A11yExemption {
+		return A11yExemption(str)
+	})
+}
+
 func fromStrings[T any](strings []string, transform func(string) T) []T {
 	res := make([]T, 0, len(strings))
 	for _, s := range strings {

pkg/manifest/a11y_test.go

@@ -26,7 +26,8 @@ func TestA11yUnmarshalFullJSON(t *testing.T) {
 		"accessMode": ["auditory", "chartOnVisual"],
 		"accessModeSufficient": [["visual", "tactile"]],
 		"feature": ["readingOrder", "alternativeText"],
-		"hazard": ["flashing", "motionSimulation"]
+		"hazard": ["flashing", "motionSimulation"],
+		"exemption": ["eaa-fundamental-alteration", "eaa-microenterprise"]
 	}`), &m))
 	assert.Equal(t, A11y{
 		ConformsTo: []A11yProfile{
@@ -57,6 +58,10 @@ func TestA11yUnmarshalFullJSON(t *testing.T) {
 			A11yHazardFlashing,
 			A11yHazardMotionSimulation,
 		},
+		Exemptions: []A11yExemption{
+			A11yExemptionEAAFundamentalAlteration,
+			A11yExemptionEAAMicroenterprise,
+		},
 	}, m, "unmarshalled JSON object should be equal to A11y object")
 }
 
@@ -101,6 +106,7 @@ func TestA11yMarshalMinimalJSON(t *testing.T) {
 		AccessModesSufficient: [][]A11yPrimaryAccessMode{},
 		Features:              []A11yFeature{},
 		Hazards:               []A11yHazard{},
+		Exemptions:            []A11yExemption{},
 	}
 	data, err := json.Marshal(m)
 	assert.NoError(t, err)
@@ -139,12 +145,16 @@ func TestA11yMarshalFullJSON(t *testing.T) {
 			A11yHazardFlashing,
 			A11yHazardMotionSimulation,
 		},
+		Exemptions: []A11yExemption{
+			A11yExemptionEAAFundamentalAlteration,
+			A11yExemptionEAAMicroenterprise,
+		},
 	}
 	data, err := json.Marshal(m)
 	assert.NoError(t, err)
 	assert.Equal(
 		t,
 		data,
-		[]byte(`{"conformsTo":["http://www.idpf.org/epub/a11y/accessibility-20170105.html#wcag-a","https://profile2"],"certification":{"certifiedBy":"company1","credential":"credential1","report":"https://report1"},"summary":"Summary","accessMode":["auditory","chartOnVisual"],"accessModeSufficient":[["auditory"],["visual","tactile"],["visual"]],"feature":["readingOrder","alternativeText"],"hazard":["flashing","motionSimulation"]}`),
+		[]byte(`{"conformsTo":["http://www.idpf.org/epub/a11y/accessibility-20170105.html#wcag-a","https://profile2"],"certification":{"certifiedBy":"company1","credential":"credential1","report":"https://report1"},"summary":"Summary","accessMode":["auditory","chartOnVisual"],"accessModeSufficient":[["auditory"],["visual","tactile"],["visual"]],"feature":["readingOrder","alternativeText"],"hazard":["flashing","motionSimulation"],"exemption":["eaa-fundamental-alteration","eaa-microenterprise"]}`),
 	)
 }

pkg/parser/epub/metadata.go

@@ -646,6 +646,7 @@ func (m PubMetadataAdapter) Accessibility() *manifest.A11y {
 	a11y.AccessModesSufficient = m.a11yAccessModesSufficient()
 	a11y.Features = m.a11yFeatures()
 	a11y.Hazards = m.a11yHazards()
+	a11y.Exemptions = m.a11yExemptions()
 
 	if a11y.IsEmpty() {
 		return nil
@@ -785,6 +786,15 @@ func (m PubMetadataAdapter) a11yHazards() []manifest.A11yHazard {
 	return hazards
 }
 
+func (m PubMetadataAdapter) a11yExemptions() []manifest.A11yExemption {
+	values := m.Values(VocabularyA11Y + "exemption")
+	hazards := make([]manifest.A11yExemption, len(values))
+	for i, v := range values {
+		hazards[i] = manifest.A11yExemption(v)
+	}
+	return hazards
+}
+
 func (m *PubMetadataAdapter) seedBelongsToData() {
 	if m._belongsToSeeded {
 		return

pkg/parser/epub/metadata_test.go

@@ -323,6 +323,7 @@ func TestMetadataEPUB2Accessibility(t *testing.T) {
 	}
 	e.Features = []manifest.A11yFeature{manifest.A11yFeatureStructuralNavigation, manifest.A11yFeatureAlternativeText}
 	e.Hazards = []manifest.A11yHazard{manifest.A11yHazardMotionSimulation, manifest.A11yHazardNoSoundHazard}
+	e.Exemptions = []manifest.A11yExemption{manifest.A11yExemptionEAAMicroenterprise, manifest.A11yExemptionEAAFundamentalAlteration}
 	assert.Equal(t, &e, m.Accessibility)
 	assert.Nil(t, m.OtherMetadata["accessibility"])
 }
@@ -345,6 +346,7 @@ func TestMetadataEPUB3Accessibility(t *testing.T) {
 	}
 	e.Features = []manifest.A11yFeature{manifest.A11yFeatureStructuralNavigation, manifest.A11yFeatureAlternativeText}
 	e.Hazards = []manifest.A11yHazard{manifest.A11yHazardMotionSimulation, manifest.A11yHazardNoSoundHazard}
+	e.Exemptions = []manifest.A11yExemption{manifest.A11yExemptionEAAMicroenterprise, manifest.A11yExemptionEAAFundamentalAlteration}
 	assert.Equal(t, &e, m.Accessibility)
 	assert.Nil(t, m.OtherMetadata["accessibility"])
 }

pkg/parser/epub/testdata/package/accessibility-epub2.opf

@@ -20,6 +20,9 @@
     <meta name="a11y:certifiedBy" content="Accessibility Testers Group"/>
     <meta name="a11y:certifierCredential" content="DAISY OK"/>
     <meta name="a11y:certifierReport" content="https://example.com/a11y-report/"/>
+
+    <meta property="a11y:exemption">eaa-microenterprise</meta>
+    <meta property="a11y:exemption">eaa-fundamental-alteration</meta>
   </metadata>
   <manifest>
     <item id="titlepage" href="titlepage.xhtml"/>

pkg/parser/epub/testdata/package/accessibility-epub3.opf

@@ -24,6 +24,9 @@
     <link rel="a11y:certifierReport" refines="#certifier2" href="https://example.com/fakereport"/>
     <link rel="a11y:certifierReport" refines="#certifier" href="https://example.com/a11y-report/"/>
 
+    <meta property="a11y:exemption">eaa-microenterprise</meta>
+    <meta property="a11y:exemption">eaa-fundamental-alteration</meta>
+
   </metadata>
   <manifest>
     <item id="titlepage" href="titlepage.xhtml"/>