fix: Update to support #101 (#124)

Signed-off-by: Mike Frederick <mike.frederick@cesium.com>
Co-authored-by: Christopher Angelo Phillips <32073428+spiffcs@users.noreply.github.com>

grant/policy.go

@@ -7,7 +7,6 @@ import (
 )
 
 // Policy is a structure of rules that define how licenses are denied
-// TODO: maybe there should be a strict option that denies all and then only allows what is explicitly allowed
 type Policy struct {
 	Rules        Rules
 	MatchNonSPDX bool
@@ -51,10 +50,6 @@ func (p Policy) IsEmpty() bool {
 // IsDenied returns true if the given license is denied by the policy
 func (p Policy) IsDenied(license License, pkg *Package) (bool, *Rule) {
 	for _, rule := range p.Rules {
-		if rule.Mode != Deny {
-			continue
-		}
-
 		var toMatch string
 		if license.IsSPDX() {
 			toMatch = strings.ToLower(license.LicenseID)
@@ -63,16 +58,27 @@ func (p Policy) IsDenied(license License, pkg *Package) (bool, *Rule) {
 		}
 
 		toMatch = strings.ToLower(toMatch)
+		// If there is a match and the content to match is not an empty string
 		if rule.Glob.Match(toMatch) && toMatch != "" {
+			var returnVal bool
+			// set the return value based on the rule mode
+			if rule.Mode == Allow {
+				returnVal = false
+			} else {
+				returnVal = true
+			}
 			if pkg == nil {
-				return true, &rule
+				return returnVal, &rule
 			}
 			for _, exception := range rule.Exceptions {
 				if exception.Match(pkg.Name) {
-					return false, &rule
+					// flip the return value based on the exception
+					returnVal = !returnVal
+
+					return returnVal, &rule
 				}
 			}
-			return true, &rule
+			return returnVal, &rule
 		}
 	}
 	return false, nil

grant/policy_test.go

@@ -114,3 +114,139 @@ func Test_Policy_DenyAll(t *testing.T) {
 		})
 	}
 }
+
+func Test_Policy_Exceptions(t *testing.T) {
+	tests := []struct {
+		name string
+		p    Policy
+		want struct {
+			denied bool
+			rule   *Rule
+		}
+	}{
+		{
+			name: "Policy Default Deny All denies all licenses",
+			p: Policy{
+				Rules: Rules{Rule{
+					Name:       "default-deny-all",
+					Glob:       glob.MustCompile("*"),
+					Exceptions: []glob.Glob{glob.MustCompile("MIT")},
+					Mode:       Deny,
+					Reason:     "grant by default will deny all licenses",
+				}},
+				MatchNonSPDX: false,
+			},
+			want: struct {
+				denied bool
+				rule   *Rule
+			}{
+				denied: false,
+				rule: &Rule{
+					Name:       "default-deny-all",
+					Glob:       glob.MustCompile("*"),
+					Exceptions: []glob.Glob{glob.MustCompile("MIT")},
+					Mode:       Deny,
+					Reason:     "grant by default will deny all licenses",
+				},
+			},
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			denied, rule := tc.p.IsDenied(License{LicenseID: "MIT", SPDXExpression: "MIT"}, &Package{ID: "MIT", Name: "MIT"})
+			if denied != tc.want.denied {
+				t.Errorf("Expected %t, got %t", tc.want.denied, denied)
+			}
+			if diff := cmp.Diff(tc.want.rule, rule); diff != "" {
+				t.Errorf("IsDenied() mismatch (-want +got):\n%s", diff)
+			}
+		})
+	}
+}
+
+func Test_Policy_Allow(t *testing.T) {
+	tests := []struct {
+		name string
+		p    Policy
+		want struct {
+			denied bool
+			rule   *Rule
+		}
+	}{
+		{
+			name: "Policy Allow MIT",
+			p: Policy{
+				Rules: Rules{Rule{
+					Name:       "allow MIT",
+					Glob:       glob.MustCompile("mit"),
+					Exceptions: []glob.Glob{},
+					Mode:       Allow,
+					Reason:     "grant allow MIT",
+				}, Rule{
+					Name:       "deny gpl",
+					Glob:       glob.MustCompile("gpl"),
+					Exceptions: []glob.Glob{},
+					Mode:       Deny,
+					Reason:     "grant deny gpl",
+				}},
+				MatchNonSPDX: false,
+			},
+			want: struct {
+				denied bool
+				rule   *Rule
+			}{
+				denied: false,
+				rule: &Rule{
+					Name:       "allow MIT",
+					Glob:       glob.MustCompile("mit"),
+					Exceptions: []glob.Glob{},
+					Mode:       Allow,
+					Reason:     "grant allow MIT",
+				},
+			},
+		},
+		{
+			name: "Policy Deny MIT",
+			p: Policy{
+				Rules: Rules{Rule{
+					Name:       "deny MIT",
+					Glob:       glob.MustCompile("mit"),
+					Exceptions: []glob.Glob{},
+					Mode:       Deny,
+					Reason:     "grant deny MIT",
+				}, Rule{
+					Name:       "allow gpl",
+					Glob:       glob.MustCompile("gpl"),
+					Exceptions: []glob.Glob{},
+					Mode:       Allow,
+					Reason:     "grant allow gpl",
+				}},
+				MatchNonSPDX: false,
+			},
+			want: struct {
+				denied bool
+				rule   *Rule
+			}{
+				denied: true,
+				rule: &Rule{
+					Name:       "deny MIT",
+					Glob:       glob.MustCompile("mit"),
+					Exceptions: []glob.Glob{},
+					Mode:       Deny,
+					Reason:     "grant deny MIT",
+				},
+			},
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			denied, rule := tc.p.IsDenied(License{LicenseID: "MIT", SPDXExpression: "MIT"}, nil)
+			if denied != tc.want.denied {
+				t.Errorf("Expected %t, got %t", tc.want.denied, denied)
+			}
+			if diff := cmp.Diff(tc.want.rule, rule); diff != "" {
+				t.Errorf("IsDenied() mismatch (-want +got):\n%s", diff)
+			}
+		})
+	}
+}