codegen.go: support seeding pager with initial nextLink

If a user wishes to resume paging from a particular link, they may pass
a parameter to the list operation method on their client. This next link
will be used for the first paging operation.

Signed-off-by: Steve Kuznetsov <[email protected]>

Author: stevekuznetsov

packages/codegen.go/src/fake/servers.ts

@@ -831,8 +831,8 @@ function parseHeaderPathQueryParams(clientPkg: string, method: go.Method, import
       // client params and parameter literals aren't passed to APIs
       continue;
     }
-    if (go.isResumeTokenParameter(param)) {
-      // skip the ResumeToken param as we don't send that back to the caller
+    if (go.isResumeTokenParameter(param) || go.isNextLinkParameter(param)) {
+      // skip the ResumeToken and NextLink params as we don't send them back to the caller
       continue;
     }
 
@@ -1183,7 +1183,7 @@ function populateApiParams(clientPkg: string, method: go.Method, paramValues: Ma
     if (helpers.isParameterGroup(param)) {
       if (param.groupName === method.optionalParamsGroup.groupName) {
         // this is the optional params type. in some cases we just pass nil
-        const countParams = values(param.params).where((each: go.Parameter) => { return !go.isResumeTokenParameter(each); }).count();
+        const countParams = values(param.params).where((each: go.Parameter) => { return !go.isResumeTokenParameter(each) && !go.isNextLinkParameter(each); }).count();
         if (countParams === 0) {
           // if the options param is empty or only contains the resume token param just pass nil
           params.push('nil');

packages/codegen.go/src/helpers.ts

@@ -104,8 +104,8 @@ export function getCreateRequestParametersSig(method: go.Method | go.NextPageMet
   for (const methodParam of values(methodParams)) {
     let paramName = uncapitalize(methodParam.name);
     // when creating the method sig for fooCreateRequest, if the options type is empty
-    // or only contains the ResumeToken param use _ for the param name to quiet the linter
-    if (isParameterGroup(methodParam) && (methodParam.params.length === 0 || (methodParam.params.length === 1 && go.isResumeTokenParameter(methodParam.params[0])))) {
+    // or only contains the ResumeToken or NextLink param use _ for the param name to quiet the linter
+    if (isParameterGroup(methodParam) && (methodParam.params.length === 0 || (methodParam.params.length === 1 && (go.isResumeTokenParameter(methodParam.params[0]) || go.isNextLinkParameter(methodParam.params[0]))))) {
       paramName = '_';
     }
     params.push(`${paramName} ${formatParameterTypeName(methodParam)}`);

packages/codegen.go/src/operations.ts

@@ -358,8 +358,11 @@ function emitPagerDefinition(client: go.Client, method: go.PageableMethod, impor
     if (!go.isLROMethod(method)) {
       text += '\t\t\tnextLink := ""\n';
       nextLinkVar = 'nextLink';
-      text += '\t\t\tif page != nil {\n';
-      text += `\t\t\t\tnextLink = *page.${method.nextLinkName}\n\t\t\t}\n`;
+      text += `\t\t\tif page != nil && page.${method.nextLinkName} != nil {\n`;
+      text += `\t\t\t\tnextLink = *page.${method.nextLinkName}\n`;
+      text += `\t\t\t} else if options != nil && options.NextLink != "" {\n`;
+      text += `\t\t\t\tnextLink = options.NextLink\n`;
+      text += `\t\t\t}\n`;
     } else {
       nextLinkVar = `*page.${method.nextLinkName}`;
     }
@@ -1234,7 +1237,7 @@ function generateLROBeginMethod(client: go.Client, method: go.LROMethod, imports
   let pollerType = 'nil';
   let pollerTypeParam = `[${method.responseEnvelope.name}]`;
   if (go.isPageableMethod(method)) {
-    // for paged LROs, we construct a pager and pass it to the LRO ctor.
+    // for paged LROs, we construct a pager and pass it to the LRO actor.
     pollerTypeParam = `[*runtime.Pager${pollerTypeParam}]`;
     pollerType = '&pager';
     text += '\tpager := ';

packages/codemodel.go/src/param.ts

@@ -181,6 +181,10 @@ export interface ResumeTokenParameter extends Parameter {
   isResumeToken: true;
 }
 
+export interface NextLinkParameter extends Parameter {
+  isNextLink: true;
+}
+
 export function isBodyParameter(param: Parameter): param is BodyParameter {
   return (<BodyParameter>param).bodyFormat !== undefined;
 }
@@ -237,6 +241,10 @@ export function isResumeTokenParameter(param: Parameter): param is ResumeTokenPa
   return (<ResumeTokenParameter>param).isResumeToken !== undefined;
 }
 
+export function isNextLinkParameter(param: Parameter): param is NextLinkParameter {
+  return (<NextLinkParameter>param).isNextLink !== undefined;
+}
+
 export function isRequiredParameter(param: Parameter): boolean {
   // parameters with a client-side default value are always optional
   if (isClientSideDefault(param.kind)) {
@@ -380,6 +388,14 @@ export class ResumeTokenParameter extends Parameter implements ResumeTokenParame
   }
 }
 
+export class NextLinkParameter extends Parameter implements NextLinkParameter {
+  constructor() {
+    super('NextLink', new type.PrimitiveType('string'), 'optional', true, 'method');
+    this.isNextLink = true;
+    this.docs.summary = 'Resumes the paging operation from the provided link.';
+  }
+}
+
 export class ClientSideDefault implements ClientSideDefault {
   constructor(defaultValue: type.LiteralValue) {
     this.defaultValue = defaultValue;

packages/typespec-go/src/tcgcadapter/clients.ts

@@ -303,6 +303,9 @@ export class clientAdapter {
       if (go.isLROMethod(method)) {
         optionalGroup.params.push(new go.ResumeTokenParameter());
       }
+      if (go.isPageableMethod(method)) {
+        optionalGroup.params.push(new go.NextLinkParameter());
+      }
     }
 
     // stuff all of the operation parameters into one array for easy traversal