fix: added invariant errors for unexpected conditions and FIXME's

Author: wyattjoh

packages/next/errors.json

@@ -788,5 +788,7 @@
   "787": "\\`experimental.clientParamParsing\\` can not be \\`true\\` when \\`experimental.clientSegmentCache\\` is \\`false\\`. Client param parsing is only relevant when client segment cache is enabled.",
   "788": "Unexpected dynamic param type: %s",
   "789": "Expected RSC response, got %s",
-  "790": "Invariant: Expected RSC response, got %s"
+  "790": "Invariant: Expected RSC response, got %s",
+  "791": "Unexpected match for a pathname \"%s\" with a param \"%s\" of type \"%s\"",
+  "792": "Unexpected empty path segments match for a pathname \"%s\" with param \"%s\" of type \"%s\""
 }

packages/next/src/build/static-paths/app.ts

@@ -26,6 +26,7 @@ import { createIncrementalCache } from '../../export/helpers/create-incremental-
 import type { NextConfigComplete } from '../../server/config-shared'
 import type { WorkStore } from '../../server/app-render/work-async-storage.external'
 import type { DynamicParamTypes } from '../../shared/lib/app-router-types'
+import { InvariantError } from '../../shared/lib/invariant-error'
 
 /**
  * Filters out duplicate parameters from a list of parameters.
@@ -596,18 +597,22 @@ export function resolveParallelRouteParams(
       // This mimics the behavior in getDynamicParam where the pagePath
       // is split and used to populate catchall values
       if (pathSegments.length > 0) {
+        // FIXME: (NAR-335) this should handle prefixed segments
         params[paramName] = pathSegments
       } else if (paramType === 'optional-catchall') {
         params[paramName] = []
       } else {
-        // For regular catchall and catchall-intercepted with no segments
-        fallbackRouteParams.push(
-          createFallbackRouteParam(paramName, paramType, true)
+        // We shouldn't be able to match a catchall segment without any path
+        // segments if it's not an optional catchall.
+        throw new InvariantError(
+          `Unexpected empty path segments match for a pathname "${pathname}" with param "${paramName}" of type "${paramType}"`
         )
       }
     } else {
-      fallbackRouteParams.push(
-        createFallbackRouteParam(paramName, paramType, true)
+      // This is some other type of route param that shouldn't get resolved
+      // statically.
+      throw new InvariantError(
+        `Unexpected match for a pathname "${pathname}" with a param "${paramName}" of type "${paramType}"`
       )
     }
   }

packages/next/src/server/request/fallback-params.ts

@@ -1,6 +1,7 @@
 import { collectFallbackRouteParams } from '../../build/segment-config/app/app-segments'
 import type { FallbackRouteParam } from '../../build/static-paths/types'
 import type { DynamicParamTypesShort } from '../../shared/lib/app-router-types'
+import { InvariantError } from '../../shared/lib/invariant-error'
 import { getRouteMatcher } from '../../shared/lib/router/utils/route-matcher'
 import { getRouteRegex } from '../../shared/lib/router/utils/route-regex'
 import { dynamicParamTypes } from '../app-render/get-short-dynamic-param-type'
@@ -139,24 +140,27 @@ export function getFallbackRouteParams(
           continue
         }
 
-        // If there are no path segments and this is not an optional catchall,
-        // we can add it to the fallback route params as the value is unknown.
         if (
           pathSegments.length === 0 &&
           fallbackRouteParam.paramType !== 'optional-catchall'
         ) {
-          fallbackRouteParams.push(fallbackRouteParam)
-          continue
+          // We shouldn't be able to match a catchall segment without any path
+          // segments if it's not an optional catchall.
+          throw new InvariantError(
+            `Unexpected empty path segments match for a pathname "${page}" with param "${fallbackRouteParam.paramName}" of type "${fallbackRouteParam.paramType}"`
+          )
         }
 
         // The path segments are not empty, and the segments didn't contain any
         // unknown params, so we know that this particular fallback route param
         // route param is not actually unknown, and is known. We can skip adding
         // it to the fallback route params.
       } else {
-        // This is some other type of route param, but it wasn't already
-        // resolved, so we can add it to the fallback route params.
-        fallbackRouteParams.push(fallbackRouteParam)
+        // This is some other type of route param that shouldn't get resolved
+        // statically.
+        throw new InvariantError(
+          `Unexpected match for a pathname "${page}" with a param "${fallbackRouteParam.paramName}" of type "${fallbackRouteParam.paramType}"`
+        )
       }
     } else if (unknownParamKeys.has(fallbackRouteParam.paramName)) {
       // As this is a non-parallel route segment, and it exists in the unknown

packages/next/src/shared/lib/router/utils/get-dynamic-param.ts

@@ -77,6 +77,7 @@ export function getDynamicParam(
 
       // handle the case where a catchall or optional catchall does not have a value,
       // e.g. `/foo/bar/hello` and `@slot/[...catchall]` or `@slot/[[...catchall]]` is matched
+      // FIXME: (NAR-335) this should handle prefixed segments
       value = pagePath
         .split('/')
         // remove the first empty string