[Akshay-2007-1]

Summary

Closes #190 on the py-slang side. input() already blocked correctly via conductor.requestInput() (the CSE machine's async generator loop suspends naturally on that await), but two things were missing:

• MiscBuiltins.input discarded its prompt argument entirely and called requestInput() with zero args.
• Nothing flushed stdout buffered by earlier print()s before blocking, so context printed just before an input() call in the same chunk wouldn't reach the user until the whole chunk finished.

Changes:

• MiscBuiltins.input now validates 0-1 args (@Validate(0, 1, "input", true)), writes the prompt to stdout before blocking (matching CPython's input(prompt), which prints the prompt with no trailing newline), and forwards it through receiveInput(context, prompt).
• createInputStream gained a setNextPrompt side-channel so its pull()-driven ReadableStream can pass a per-call prompt to conductor.requestInput(prompt) — pull() itself has no visibility into per-call arguments.
• receiveInput now flushes any buffered stdout (via a new optional context.streams.flushStdout hook, wired up in PyCseEvaluator.evaluateChunk) before blocking.
• Added src/tests/input.test.ts covering both the with- and without-prompt paths.

Depends on

This depends on an unreleased Conductor protocol change adding requestInput(prompt?: string) / IHostPlugin.receiveInputRequest: source-academy/conductor#40. Until that merges and a new tag is cut, this branch points @sourceacademy/conductor at a local portal: dev resolution in package.json/yarn.lock — that needs to be repinned to the real published tag before merge, and this PR should probably stay in draft/blocked until then.

Note for reviewers: the portal: symlink currently breaks this repo's jest.config.js locally (its moduleNameMapper/transformIgnorePatterns for @sourceacademy/conductor assume a real node_modules directory, not a symlink resolving outside rootDir) — verified correctness by temporarily swapping in a physical copy of the built conductor package for test runs. This resolves itself once the portal pin is replaced with a real release.

Test plan

• tsc --noEmit passes clean
• jest src/tests/input.test.ts passes (2/2)
• Full jest src/tests/stdlib.test.ts suite passes (1812/1812), confirming no regressions
• Manual verification in a running frontend still pending (blocked on the frontend-side PR, not yet opened)

[gemini-code-assist]

Code Review

This pull request adds support for prompts in the Python input() built-in function, ensuring that any buffered stdout is flushed before blocking on stdin, and passing the prompt to the conductor. A critical issue was identified in createInputStream where the default highWaterMark of 1 on ReadableStream triggers an eager pull() upon initialization, causing the first prompt to be bypassed. Setting highWaterMark: 0 is recommended to ensure input is only pulled on-demand.

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[Akshay-2007-1]

@coderabbitai, any review?

[coderabbitai]

@Akshay-2007-1 Sure, I'll take a look now. Note that the PR description mentions this depends on an unreleased Conductor change (source-academy/conductor#40) and currently points @sourceacademy/conductor at a local portal: dev resolution that needs to be repinned before merge — I'll flag anything related to that as well, but you'll want to repin before this is mergeable regardless of the review outcome.

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[coderabbitai]

Walkthrough

Adds prompt support to the Python input() builtin: a new InputStreamContext type with setNextPrompt, updated createInputStream/receiveInput sequencing that flushes stdout before requesting input, wiring of flushStdout through evaluator and runner streams, updated input() builtin behavior, new tests, and an unrelated package.json dependency resolution override.

Changes

Prompt-aware input() flow

Layer / File(s)	Summary
InputStreamContext type and Context streams contract src/engines/cse/context.ts, src/engines/cse/streams.ts	Context.streams.stdin now uses InputStreamContext with an optional flushStdout field; InputStreamContext adds setNextPrompt, and createInputStream tracks pendingPrompt with highWaterMark: 0 to avoid phantom pulls.
receiveInput sequencing and input() builtin src/engines/cse/streams.ts, src/stdlib/misc.ts	receiveInput accepts an optional prompt, flushes stdout, then sets the stdin prompt before reading; MiscBuiltins.input validates 0–1 args, prints the prompt without a newline, and forwards it to receiveInput.
Evaluator and runner stream wiring src/conductor/PyCseEvaluator.ts, src/runner.ts	PyCseEvaluator wires flushStdout to flushOutput(conductor); makeMemoryStreams adds a setNextPrompt no-op on stdin.
Input prompt tests and mocks src/tests/input.test.ts, src/tests/utils.ts	New tests cover prompt/no-prompt input() behavior and prompt ordering via real createInputStream/receiveInput; the shared test stdin mock gains setNextPrompt.

Dependency Resolution Override

Layer / File(s)	Summary
package.json resolutions override package.json	Adds a resolutions block forcing @sourceacademy/conductor to a local portal path.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Sequence Diagram(s)

sequenceDiagram
  participant PythonProgram
  participant MiscBuiltinsInput
  participant ReceiveInput
  participant StdinStream
  participant Conductor

  PythonProgram->>MiscBuiltinsInput: input(prompt)
  MiscBuiltinsInput->>MiscBuiltinsInput: displayOutput(prompt)
  MiscBuiltinsInput->>ReceiveInput: receiveInput(context, prompt)
  ReceiveInput->>ReceiveInput: flushStdout()
  ReceiveInput->>StdinStream: setNextPrompt(prompt)
  StdinStream->>Conductor: requestInput(pendingPrompt)
  Conductor-->>StdinStream: response
  StdinStream-->>ReceiveInput: value
  ReceiveInput-->>MiscBuiltinsInput: typed value

Loading

Poem

A rabbit hops to fetch a line,
"Write your string here:" — right on time!
Stdout flushed before I wait,
No more hanging at the gate. 🐰
Prompt by prompt, in order true,
Hop, hop, input()— all for you!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Out of Scope Changes check	⚠️ Warning	The temporary portal resolution in package.json is unrelated to the input() fix and appears to be a merge-blocking dev pin.	Remove the local portal resolution and repin @sourceacademy/conductor to the intended published release before merging.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main feature fix: forwarding prompts through Conductor and flushing pending stdout.
Description check	✅ Passed	The description is directly related to the changeset and explains the input prompt and stdout flush fixes.
Linked Issues check	✅ Passed	The changes implement the reported input() behavior fix, including prompt handling, stdout flushing, and regression tests.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

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• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@package.json`:
- Around line 85-87: The package.json resolutions block still pins
`@sourceacademy/conductor` to a machine-specific portal:/home/vakshay/conductor
path, which must be removed before merge. Update the resolutions entry in
package.json to point to a published release or a git URL pinned to a specific
commit/tag, using the `@sourceacademy/conductor` resolution key so the project
builds reproducibly in CI and for other developers.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 04140fee-f461-466b-b00e-f2c8246f2735

📥 Commits

Reviewing files that changed from the base of the PR and between 738e518 and c5a782b.

⛔ Files ignored due to path filters (1)

• yarn.lock is excluded by !**/yarn.lock, !**/*.lock

📒 Files selected for processing (8)

• package.json
• src/conductor/PyCseEvaluator.ts
• src/engines/cse/context.ts
• src/engines/cse/streams.ts
• src/runner.ts
• src/stdlib/misc.ts
• src/tests/input.test.ts
• src/tests/utils.ts

[martin-henz]

Looks good. This is a nice example for using the channel communication between an evaluator and the frontend.