Adds missing Params support in v1 configurability

[inlined]

Requires adding support for new features such as string interpolation (API propsoal oustanding) and value-only transforms (API proposal not outstanding beause the API is not publicly released)

Customers can now say cool things like:

import * as functions from "firebase-functions/v1";
import { onSchedule } from "firebase-functions/scheduler"

const topic = defineString("TOPIC");
const period = defineNumber("HOW_OFTEN");

export const pubSubSample = functions.pubsub.topic(topic).onPublish(() => undefined);
export const scheduleSample = onSchedule(expr`every ${period} days`, () => undefined);

For other language implications, see proposal.

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the configurability of Firebase Functions v1 by introducing support for dynamic parameter values. It enables developers to use string interpolation and value-only transformations within function definitions, leading to more flexible and reusable function configurations across different services.

Highlights

• Enhanced Parameter Support: Introduced new capabilities for handling parameters in Firebase Functions v1, specifically enabling string interpolation and value-only transformations.
• New expr Template Tag: Added an expr template tag that allows for string interpolation within parameter expressions, making it possible to embed dynamic values directly into resource paths and schedules.
• New transform Function: Implemented a transform function to apply custom transformations to string literals or existing string expressions, providing more flexibility in parameter manipulation.
• Provider Integration: Updated various Firebase Functions v1 providers (Analytics, Database, Firestore, PubSub, Storage) to accept Expression<string> types for trigger resources and schedule configurations, allowing dynamic parameter usage in these contexts.

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Changelog

• spec/params/params.spec.ts
  • Imported transform function for testing.
  • Added new test suites for the expr template tag, covering various interpolation scenarios.
  • Added new test suite for the transform function, testing both string literals and expressions.
• src/params/index.ts
  • Exported InterpolationExpression from ./types.
  • Added a new expr function that acts as a template tag for creating InterpolationExpression instances.
• src/params/types.ts
  • Defined InterpolationExpression class to handle string interpolation with template literals.
  • Defined TransformedStringExpression class to apply custom transformations to string values or expressions.
  • Introduced celOf function to retrieve the CEL representation of an argument, similar to valueOf.
  • Added transform function to create TransformedStringExpression instances.
• src/v1/cloud-functions.ts
  • Imported celOf, valueOf, and Expression from ../params/types.
  • Updated MakeCloudFunctionArgs interface to allow triggerResource to return string | Expression<string>.
  • Modified makeCloudFunction to use celOf when setting the resource for event triggers and schedule triggers.
  • Added logic to convert scheduleTrigger.timeZone to its CEL representation if it's an Expression.
  • Updated _makeParams function to accept triggerResourceGetter that can return string | Expression<string>.
  • Applied valueOf to the result of triggerResourceGetter in _makeParams to get the runtime string value.
• src/v1/function-configuration.ts
  • Updated the Schedule interface to allow schedule and timeZone properties to accept Expression<string> in addition to string or ResetValue.
• src/v1/providers/analytics.ts
  • Imported Expression from ../../params/types and expr from ../../params.
  • Modified event and _eventWithOptions functions to accept analyticsEventType as string | Expression<string>.
  • Updated the triggerResource getter in _eventWithOptions to use the new expr template tag for constructing the resource path.
  • Updated AnalyticsEventBuilder constructor to accept triggerResource that can return string | Expression<string>.
• src/v1/providers/database.ts
  • Imported Expression and transform from ../../params/types and expr from ../../params.
  • Modified instance and ref functions to accept instance and path as string | Expression<string>.
  • Updated _instanceWithOptions and _refWithOptions to handle instance and path as string | Expression<string>.
  • Used transform for normalizePath and expr for constructing resource paths in InstanceBuilder and _refWithOptions.
  • Updated InstanceBuilder and RefBuilder constructors to accept triggerResource that can return string | Expression<string>.
  • Corrected error message string concatenation.
• src/v1/providers/firestore.ts
  • Imported Expression from ../../params/types and expr from ../../params.
  • Removed posix import as it's no longer directly used for path joining.
  • Modified document, namespace, database, _databaseWithOptions, _namespaceWithOptions, _documentWithOptions functions to accept string | Expression<string> for their respective parameters.
  • Updated DatabaseBuilder and NamespaceBuilder constructors to handle string | Expression<string> for database and namespace.
  • Refactored NamespaceBuilder's document method to use the expr template tag for constructing the trigger resource path, supporting dynamic namespaces and paths.
  • Updated DocumentBuilder constructor to accept triggerResource that can return string | Expression<string>.
• src/v1/providers/pubsub.ts
  • Imported Expression from ../../params/types and expr from ../../params.
  • Modified topic and schedule functions to accept string | Expression<string> for their parameters.
  • Updated _topicWithOptions to handle topic as string | Expression<string>, including a type check for topic name validation.
  • Updated _topicWithOptions to use the expr template tag for constructing the topic resource path.
  • Updated _scheduleWithOptions to handle schedule as string | Expression<string> and to store its CEL representation in options.schedule.
  • Updated TopicBuilder and ScheduleBuilder constructors to accept triggerResource that can return string | Expression<string>.
• src/v1/providers/storage.ts
  • Imported Expression from ../../params/types and expr from ../../params.
  • Modified bucket function to accept an optional bucket parameter as string | Expression<string>.
  • Updated _bucketWithOptions to handle bucket as string | Expression<string>, including a type check for bucket name validation.
  • Updated _bucketWithOptions to use the expr template tag for constructing the bucket resource path.
  • Updated BucketBuilder and ObjectBuilder constructors to accept triggerResource that can return string | Expression<string>.

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[gemini-code-assist]

Code Review

This pull request adds significant configurability to v1 functions by introducing support for Expression types in trigger definitions, including a new expr template literal for string interpolation and a transform function for runtime value manipulation. The changes are extensive and well-applied across different providers. I've identified one high-severity issue in TransformedStringExpression that could lead to invalid CEL generation, and I've provided a suggestion to fix it. Overall, this is a great enhancement.

[gemini-code-assist]

The toString() implementation for TransformedStringExpression can lead to invalid CEL generation when used inside other expressions.

1. When source is an Expression, toString() incorrectly returns this.source.toCEL(), which includes {{...}}. This causes nested braces (e.g., {{ {{...}} }}) when the TransformedStringExpression is part of another expression.
2. When source is a string, toString() returns the transformed string without quotes. This will be treated as an identifier instead of a string literal in the generated CEL.

The toString() method should return the unwrapped CEL for expressions and a properly quoted string for literals. A test case that would have caught this is:

it("handles transformed expressions inside other expressions", () => {
  const p = params.defineString("P");
  const t = transform(p, (s) => s.toUpperCase());
  const b = params.defineBoolean("B");
  expect(b.thenElse(t, "foo").toCEL()).to.equal('{{ params.B ? params.P : "foo" }}');
});

Suggested change

	return this.source instanceof Expression ? this.source.toCEL() : this.transformer(this.source);
	return this.source instanceof Expression ? this.source.toString() : JSON.stringify(this.transformer(this.source));