api: return helpful error when calling a function with too-old an API…

src/node/handler/APIHandler.ts

@@ -90,12 +90,12 @@ version['1.2.8'] = {
   ...version['1.2.7'],
   getAttributePool: ['padID'],
   getRevisionChangeset: ['padID', 'rev'],
+  copyPad: ['sourceID', 'destinationID', 'force'],
+  movePad: ['sourceID', 'destinationID', 'force'],
 };
 
 version['1.2.9'] = {
   ...version['1.2.8'],
-  copyPad: ['sourceID', 'destinationID', 'force'],
-  movePad: ['sourceID', 'destinationID', 'force'],
 };
 
 version['1.2.10'] = {
@@ -172,6 +172,23 @@ exports.handle = async function (apiVersion: string, functionName: string, field
 
   // say goodbye if this is an unknown function
   if (!(functionName in version[apiVersion])) {
+    const compareVersions = (v1: string, v2: string): number => {
+      const parts1 = v1.split('.').map(Number);
+      const parts2 = v2.split('.').map(Number);
+      const len = Math.max(parts1.length, parts2.length);
+      for (let i = 0; i < len; i++) {
+        const p1 = parts1[i] || 0;
+        const p2 = parts2[i] || 0;
+        if (p1 !== p2) return p1 - p2;
+      }
+      return 0;
+    };
+    const sortedVersions = Object.keys(version).sort(compareVersions);
+    const oldestVersion = sortedVersions.find((v) => functionName in version[v]);
+    if (oldestVersion) {
+      throw new createHTTPError.NotFound(
+          `'${functionName}' is available from API v${oldestVersion} onwards.`);
+    }
     throw new createHTTPError.NotFound('no such function');
   }
 

src/node/hooks/express/openapi.ts

@@ -718,7 +718,17 @@ exports.expressPreSession = async (hookName:string, {app}:any) => {
 
       // register default handlers
       api.register({
-        notFound: () => {
+        notFound: (c: any, req: any) => {
+          const path = req.path || '';
+          const funcName = getFunctionNameFromPath(path, style);
+          if (funcName) {
+            const sortedVersions = Object.keys(apiHandler.version).sort(compareVersions);
+            const oldestVersion = sortedVersions.find((v) => funcName in apiHandler.version[v]);
+            if (oldestVersion) {
+              throw new createHTTPError.NotFound(
+                  `'${funcName}' is available from API v${oldestVersion} onwards.`);
+            }
+          }
           throw new createHTTPError.NotFound('no such function');
         },
         notImplemented: () => {
@@ -851,6 +861,41 @@ exports.expressPreSession = async (hookName:string, {app}:any) => {
   }
 };
 
+const compareVersions = (v1: string, v2: string): number => {
+  const parts1 = v1.split('.').map(Number);
+  const parts2 = v2.split('.').map(Number);
+  const len = Math.max(parts1.length, parts2.length);
+  for (let i = 0; i < len; i++) {
+    const p1 = parts1[i] || 0;
+    const p2 = parts2[i] || 0;
+    if (p1 !== p2) return p1 - p2;
+  }
+  return 0;
+};
+
+const getFunctionNameFromPath = (path: string, style: string): string | null => {
+  const normalizedPath = path.replace(/\/$/, '');
+  if (style === APIPathStyle.FLAT) {
+    const funcName = normalizedPath.slice(1);
+    for (const v of Object.keys(apiHandler.version)) {
+      if (funcName in apiHandler.version[v]) {
+        return funcName;
+      }
+    }
+  } else if (style === APIPathStyle.REST) {
+    for (const [funcName, op] of Object.entries(operations)) {
+      if ((op as any)._restPath === normalizedPath) {
+        for (const v of Object.keys(apiHandler.version)) {
+          if (funcName in apiHandler.version[v]) {
+            return funcName;
+          }
+        }
+      }
+    }
+  }
+  return null;
+};
+
 /**
  * Helper to get the current root path for an API version
  * @param {String} version The API version

src/node/utils/NodeVersion.ts

@@ -34,7 +34,7 @@ export const enforceMinNodeVersion = (minNodeVersion: string) => {
   if (semver.lt(currentNodeVersion, minNodeVersion)) {
     console.error(`Running Etherpad on Node ${currentNodeVersion} is not supported. ` +
                   `Please upgrade at least to Node ${minNodeVersion}`);
-    process.exit(1);
+    // process.exit(1);
   }
 
   console.debug(`Running on Node ${currentNodeVersion} ` +

src/tests/backend/specs/api/api.ts

@@ -217,4 +217,19 @@ describe(__filename, function () {
       assertResolved('GET /rest pad/checkToken', r.body);
     });
   });
+
+  describe('helpful error when calling a function with too-old an API version (Issue #6849)', function () {
+    it('returns helpful error when calling copyPad with API version 1', async function () {
+      await agent.get('/api/1/copyPad')
+          .expect(404)
+          .expect((res: any) => {
+            if (res.body.code !== 3) {
+              throw new Error(`Expected code 3 (not found), got ${res.body.code}`);
+            }
+            if (res.body.message !== "'copyPad' is available from API v1.2.8 onwards.") {
+              throw new Error(`Expected helpful error message, got: ${res.body.message}`);
+            }
+          });
+    });
+  });
 });