refactor: Improve validation logic and test clarity

This commit includes several improvements to the function configuration validation:

-   The error message for duplicate `source`/`prefix` pairs is now more descriptive and suggests a solution.
-   The test suite is more robust, with more specific error message checks and improved typing.
-   Linter warnings have been addressed.

Author: taeold

src/functions/projectConfig.spec.ts

@@ -43,37 +43,39 @@ describe("projectConfig", () => {
     });
 
     it("passes validation for multi-instance config with same source", () => {
-      const config = [
+      const config: projectConfig.NormalizedConfig = [
         { source: "foo", codebase: "bar" },
         { source: "foo", codebase: "baz", prefix: "prefix-two" },
       ];
-      expect(projectConfig.validate(config as projectConfig.NormalizedConfig)).to.deep.equal(
-        config,
-      );
+      expect(projectConfig.validate(config)).to.deep.equal(config);
     });
 
     it("passes validation for multi-instance config with one missing codebase", () => {
-      const config = [{ source: "foo", codebase: "bar", prefix: "bar-prefix" }, { source: "foo" }];
+      const config: projectConfig.NormalizedConfig = [
+        { source: "foo", codebase: "bar", prefix: "bar-prefix" },
+        { source: "foo" },
+      ];
       const expected = [
         { source: "foo", codebase: "bar", prefix: "bar-prefix" },
         { source: "foo", codebase: "default" },
       ];
-      expect(projectConfig.validate(config as projectConfig.NormalizedConfig)).to.deep.equal(
-        expected,
-      );
+      expect(projectConfig.validate(config)).to.deep.equal(expected);
     });
 
     it("fails validation for multi-instance config with missing codebase and a default codebase", () => {
-      const config = [{ source: "foo", codebase: "default" }, { source: "foo" }];
-      expect(() => projectConfig.validate(config as projectConfig.NormalizedConfig)).to.throw(
+      const config: projectConfig.NormalizedConfig = [
+        { source: "foo", codebase: "default" },
+        { source: "foo" },
+      ];
+      expect(() => projectConfig.validate(config)).to.throw(
         FirebaseError,
         /functions.codebase must be unique but 'default' was used more than once./,
       );
     });
 
     it("fails validation for multi-instance config with multiple missing codebases", () => {
-      const config = [{ source: "foo" }, { source: "foo" }];
-      expect(() => projectConfig.validate(config as projectConfig.NormalizedConfig)).to.throw(
+      const config: projectConfig.NormalizedConfig = [{ source: "foo" }, { source: "foo" }];
+      expect(() => projectConfig.validate(config)).to.throw(
         FirebaseError,
         /functions.codebase must be unique but 'default' was used more than once./,
       );
@@ -119,22 +121,31 @@ describe("projectConfig", () => {
     });
 
     it("fails validation given a duplicate source/prefix pair", () => {
-      const config = [
+      const config: projectConfig.NormalizedConfig = [
         { source: "foo", codebase: "bar", prefix: "a" },
         { source: "foo", codebase: "baz", prefix: "a" },
       ];
-      expect(() => projectConfig.validate(config as projectConfig.NormalizedConfig)).to.throw(
+      expect(() => projectConfig.validate(config)).to.throw(
         FirebaseError,
-        /More than one functions config specifies the same source directory/,
+        /More than one functions config specifies the same source directory \('foo'\) and prefix \('a'\)/,
+      );
+    });
+
+    it("fails validation for multi-instance config with same source and no prefixes", () => {
+      const config: projectConfig.NormalizedConfig = [
+        { source: "foo", codebase: "bar" },
+        { source: "foo", codebase: "baz" },
+      ];
+      expect(() => projectConfig.validate(config)).to.throw(
+        FirebaseError,
+        /More than one functions config specifies the same source directory \('foo'\) and prefix \(''\)/,
       );
     });
 
     it("should allow a single function in an array to have a default codebase", () => {
-      const config = [{ source: "foo" }];
+      const config: projectConfig.NormalizedConfig = [{ source: "foo" }];
       const expected = [{ source: "foo", codebase: "default" }];
-      expect(projectConfig.validate(config as projectConfig.NormalizedConfig)).to.deep.equal(
-        expected,
-      );
+      expect(projectConfig.validate(config)).to.deep.equal(expected);
     });
   });
 

src/functions/projectConfig.ts

@@ -2,7 +2,7 @@ import { FunctionsConfig, FunctionConfig } from "../firebaseConfig";
 import { FirebaseError } from "../error";
 
 export type NormalizedConfig = [FunctionConfig, ...FunctionConfig[]];
-export type ValidatedSingle = FunctionConfig & { source:string; codebase: string };
+export type ValidatedSingle = FunctionConfig & { source: string; codebase: string };
 export type ValidatedConfig = [ValidatedSingle, ...ValidatedSingle[]];
 
 export const DEFAULT_CODEBASE = "default";
@@ -92,10 +92,14 @@ export function assertUnique(
 function assertUniqueSourcePrefixPair(config: ValidatedConfig): void {
   const sourcePrefixPairs = new Set<string>();
   for (const c of config) {
-    const key = `${c.source || ""}-${c.prefix || ""}`;
+    const key = `${c.source}-${c.prefix || ""}`;
     if (sourcePrefixPairs.has(key)) {
       throw new FirebaseError(
-        `More than one functions config specifies the same source directory ('${c.source}') and function name prefix ('${c.prefix || ""}').`,
+        `More than one functions config specifies the same source directory ('${
+          c.source
+        }') and prefix ('${
+          c.prefix ?? ""
+        }'). Please add a unique 'prefix' to each function configuration that shares this source to resolve the conflict.`,
       );
     }
     sourcePrefixPairs.add(key);
@@ -130,4 +134,4 @@ export function configForCodebase(config: ValidatedConfig, codebase: string): Va
     throw new FirebaseError(`No functions config found for codebase ${codebase}`);
   }
   return codebaseCfg;
-}
+}