fix: reuse path parameters for repeated templates

tests/templates.test.ts

@@ -34,6 +34,35 @@ describe('resolveTemplateUrl', () => {
     ).toBe('https://en.wikipedia.org/wiki/Django');
   });
 
+  it('reuses pathParam for repeated occurrences of the first template variable', () => {
+    expect(
+      resolveTemplateUrl({
+        targetUrl: 'https://example.com/{query}/{query}',
+        pathParam: 'foo bar',
+        query: params(),
+      }),
+    ).toBe('https://example.com/foo%20bar/foo%20bar');
+  });
+
+  it('lets matching query params override pathParam for all repeated occurrences', () => {
+    expect(
+      resolveTemplateUrl({
+        targetUrl: 'https://example.com/{query}/{query}',
+        pathParam: 'from-path',
+        query: params('query=from query'),
+      }),
+    ).toBe('https://example.com/from%20query/from%20query');
+  });
+
+  it('reuses a default value for repeated occurrences of the same template variable', () => {
+    expect(
+      resolveTemplateUrl({
+        targetUrl: 'https://example.com/{query,default=hello world}/{query,default=hello world}',
+        query: params(),
+      }),
+    ).toBe('https://example.com/hello%20world/hello%20world');
+  });
+
   it('lets matching query params override pathParam and defaults', () => {
     expect(
       resolveTemplateUrl({

worker/lib/templates.ts

@@ -38,12 +38,13 @@ export function resolveTemplateUrl(input: TemplateInput): string {
   }
 
   let parameterIndex = 0;
+  const firstParameterName = parameters[0].name;
 
   return input.targetUrl.replace(TEMPLATE_PATTERN, () => {
     const parameter = parameters[parameterIndex];
     parameterIndex += 1;
 
-    const value = resolveParameterValue(parameter, input);
+    const value = resolveParameterValue(parameter, input, firstParameterName);
     return encodeURIComponent(value);
   });
 }
@@ -82,13 +83,13 @@ function unquoteDefault(value: string): string {
   return value;
 }
 
-function resolveParameterValue(parameter: TemplateParameter, input: TemplateInput): string {
+function resolveParameterValue(parameter: TemplateParameter, input: TemplateInput, firstParameterName: string): string {
   const queryValue = input.query.get(parameter.name);
   if (queryValue !== null) {
     return queryValue;
   }
 
-  if (parameter.index === 0 && input.pathParam !== undefined) {
+  if (parameter.name === firstParameterName && input.pathParam !== undefined) {
     return input.pathParam;
   }