fix: add expected tests for templates

internal/httprule/template.go

@@ -228,7 +228,11 @@ func (p *parser) parseLiteral() (string, error) {
 		break
 	}
 	if len(literal) == 0 {
-		return "", fmt.Errorf("expected literal at %d, found %q", startPos-1, p.tok)
+		tok := fmt.Sprintf("%q", p.tok)
+		if p.tok == -1 {
+			tok = "EOF"
+		}
+		return "", fmt.Errorf("expected literal at position %d, found %s", startPos-1, tok)
 	}
 	return string(literal), nil
 }
@@ -245,7 +249,11 @@ func (p *parser) parseIdent() (string, error) {
 		break
 	}
 	if len(ident) == 0 {
-		return "", fmt.Errorf("expected identifier at %d, found %q", startPos-1, p.tok)
+		tok := fmt.Sprintf("%q", p.tok)
+		if p.tok == -1 {
+			tok = "EOF"
+		}
+		return "", fmt.Errorf("expected identifier at position %d, found %s", startPos-1, tok)
 	}
 	return string(ident), nil
 }
@@ -274,7 +282,11 @@ func (p *parser) peekN(n int) rune {
 
 func (p *parser) expect(r rune) error {
 	if p.tok != r {
-		return fmt.Errorf("expected token %q, got %q at position %d", r, p.tok, p.pos-1)
+		tok := fmt.Sprintf("%q", p.tok)
+		if p.tok == -1 {
+			tok = "EOF"
+		}
+		return fmt.Errorf("expected token %q at position %d, found %s", r, p.pos, tok)
 	}
 	p.next()
 	return nil
@@ -342,12 +354,12 @@ func validate(t Template) error {
 			continue
 		}
 		if s.Kind == SegmentKindMatchMultiple {
-			return fmt.Errorf("'**' only allowed as the last part of the template")
+			return fmt.Errorf("'**' only allowed as last part of template")
 		}
 		if s.Kind == SegmentKindVariable {
 			for _, s2 := range s.Variable.Segments {
 				if s2.Kind == SegmentKindMatchMultiple {
-					return fmt.Errorf("'**' only allowed as the last part of the template")
+					return fmt.Errorf("'**' only allowed as last part of template")
 				}
 			}
 		}
@@ -366,5 +378,25 @@ func validate(t Template) error {
 			}
 		}
 	}
+	// check for top level expansions
+	for _, s := range t.Segments {
+		if s.Kind == SegmentKindMatchSingle {
+			return fmt.Errorf("'*' must only be used in variables")
+		}
+		if s.Kind == SegmentKindMatchMultiple {
+			return fmt.Errorf("'**' must only be used in variables")
+		}
+	}
+	// check for duplicate variable bindings
+	seen := make(map[string]struct{})
+	for _, s := range t.Segments {
+		if s.Kind == SegmentKindVariable {
+			field := s.Variable.FieldPath.String()
+			if _, ok := seen[s.Variable.FieldPath.String()]; ok {
+				return fmt.Errorf("variable '%s' bound multiple times", field)
+			}
+			seen[field] = struct{}{}
+		}
+	}
 	return nil
 }

internal/httprule/template_test.go

@@ -199,21 +199,25 @@ func Test_ParseTemplate(t *testing.T) {
 
 func Test_ParseTemplate_Invalid(t *testing.T) {
 	t.Parallel()
-	for _, tt := range []string{
-		"",
-		"//",
-		"/v1:",
-		"/v1/:",
-		"/{name=messages/{id}}",
-		"/**/*",
-		"v1/messages/*",
-		"v1/{id}/{id}",
+	for _, tt := range []struct {
+		template string
+		expected string
+	}{
+		{template: "", expected: "expected token '/' at position 0, found EOF"},
+		{template: "//", expected: "expected literal at position 1, found '/'"},
+		{template: "/v1:", expected: "expected literal at position 3, found EOF"},
+		{template: "/v1/:", expected: "expected literal at position 4, found ':'"},
+		{template: "/{name=messages/{id}}", expected: "nested variable segment is not allowed"},
+		{template: "/**/*", expected: "'**' only allowed as last part of template"},
+		{template: "/v1/messages/*", expected: "'*' must only be used in variables"},
+		{template: "/v1/{id}/{id}", expected: "variable 'id' bound multiple times"},
 	} {
 		tt := tt
-		t.Run(tt, func(t *testing.T) {
+		t.Run(tt.template, func(t *testing.T) {
 			t.Parallel()
-			_, err := ParseTemplate(tt)
+			_, err := ParseTemplate(tt.template)
 			assert.Check(t, err != nil)
+			assert.ErrorContains(t, err, tt.expected)
 		})
 	}
 }