feat: introduce problem severity levels

lint/problem.go

@@ -21,6 +21,32 @@ import (
 	"github.com/jhump/protoreflect/desc"
 )
 
+type SeverityLevel int
+
+// Different levels of problem severity.
+const (
+	UnknownSeverity  SeverityLevel = 0
+	LowSeverity      SeverityLevel = 100
+	ModerateSeverity SeverityLevel = 200
+	MajorSeverity    SeverityLevel = 300
+	CriticalSeverity SeverityLevel = 400
+)
+
+func (sv SeverityLevel) String() string {
+	severity := "UNKNOWN"
+	switch sv {
+	case LowSeverity:
+		severity = "LOW"
+	case ModerateSeverity:
+		severity = "MODERATE"
+	case MajorSeverity:
+		severity = "MAJOR"
+	case CriticalSeverity:
+		severity = "CRITICAL"
+	}
+	return severity
+}
+
 // Problem contains information about a result produced by an API Linter.
 //
 // All rules return []Problem. Most lint rules return 0 or 1 problems, but
@@ -61,6 +87,13 @@ type Problem struct {
 
 	// nolint:structcheck,unused
 	noPositional struct{}
+
+	// Severity represents the criticality level of the problem. The higher
+	// the severity, the more critical the violation and the need of fixing it.
+	//
+	// It can be used to categorize problems and decide which of them are
+	// "no-gos" and which are simply informational and can be tolerated.
+	Severity SeverityLevel
 }
 
 // MarshalJSON defines how to represent a Problem in JSON.
@@ -84,19 +117,21 @@ func (p Problem) marshal() interface{} {
 
 	// Return a marshal-able structure.
 	return struct {
-		Message    string       `json:"message" yaml:"message"`
-		Suggestion string       `json:"suggestion,omitempty" yaml:"suggestion,omitempty"`
-		Location   fileLocation `json:"location" yaml:"location"`
-		RuleID     RuleName     `json:"rule_id" yaml:"rule_id"`
-		RuleDocURI string       `json:"rule_doc_uri" yaml:"rule_doc_uri"`
-		Category   string       `json:"category,omitempty" yaml:"category,omitempty"`
+		Message    string        `json:"message" yaml:"message"`
+		Suggestion string        `json:"suggestion,omitempty" yaml:"suggestion,omitempty"`
+		Location   fileLocation  `json:"location" yaml:"location"`
+		RuleID     RuleName      `json:"rule_id" yaml:"rule_id"`
+		RuleDocURI string        `json:"rule_doc_uri" yaml:"rule_doc_uri"`
+		Category   string        `json:"category,omitempty" yaml:"category,omitempty"`
+		Severity   SeverityLevel `json:"severity,omitempty" yaml:"severity,omitempty"`
 	}{
 		p.Message,
 		p.Suggestion,
 		fileLocationFromPBLocation(loc),
 		p.RuleID,
 		getRuleURL(string(p.RuleID), ruleURLMappings),
 		p.category,
+		p.Severity,
 	}
 }
 

lint/problem_test.go

@@ -29,6 +29,7 @@ func TestProblemJSON(t *testing.T) {
 		Message:  "foo bar",
 		Location: &dpb.SourceCodeInfo_Location{Span: []int32{2, 0, 42}},
 		RuleID:   "core::0131",
+		Severity: LowSeverity,
 	}
 	serialized, err := json.Marshal(problem)
 	if err != nil {
@@ -43,6 +44,7 @@ func TestProblemJSON(t *testing.T) {
 		{"ColumnNumberStart", `"column_number":1`},
 		{"ColumnNumberEnd", `"column_number":42`},
 		{"RuleID", `"rule_id":"core::0131"`},
+		{"Severity", `"severity":100`},
 	}
 	for _, test := range tests {
 		t.Run(test.testName, func(t *testing.T) {
@@ -58,6 +60,7 @@ func TestProblemYAML(t *testing.T) {
 		Message:  "foo bar",
 		Location: &dpb.SourceCodeInfo_Location{Span: []int32{2, 0, 5, 70}},
 		RuleID:   "core::0131",
+		Severity: LowSeverity,
 	}
 	serialized, err := yaml.Marshal(problem)
 	if err != nil {
@@ -73,6 +76,7 @@ func TestProblemYAML(t *testing.T) {
 		{"ColumnNumberStart", `column_number: 1`},
 		{"ColumnNumberEnd", `column_number: 70`},
 		{"RuleID", `rule_id: core::0131`},
+		{"Severity", `severity: 100`},
 	}
 	for _, test := range tests {
 		t.Run(test.testName, func(t *testing.T) {
@@ -93,6 +97,7 @@ func TestProblemDescriptor(t *testing.T) {
 		Message:    "foo bar",
 		Descriptor: m,
 		RuleID:     "core::0131",
+		Severity:   LowSeverity,
 	}
 	serialized, err := yaml.Marshal(problem)
 	if err != nil {
@@ -107,6 +112,7 @@ func TestProblemDescriptor(t *testing.T) {
 		{"ColumnNumberStart", `column_number: 1`},
 		{"ColumnNumberEnd", `column_number: 79`},
 		{"RuleID", `rule_id: core::0131`},
+		{"Severity", `severity: 100`},
 	}
 	for _, test := range tests {
 		t.Run(test.testName, func(t *testing.T) {