fix(core/pre-process, core/post-process): Run async functions in order

[kfranqueiro]

Fixes #4961.

• Updates pre/post-process tests to include verification of invocation order
  • Adds a counter shared between invocations that is incremented and output for each one
  • Changes existing toBe expectations to toContain for pass/fail without order
  • Adds new test with precise toBe expectations including order
• Revises code flow of pre- and post-process to use for...of with an await on each iteration, instead of map that invokes every function up-front followed by Promise.all
  • Note: the changes to the plugins are easier to read with whitespace ignored (?w=1).

The new test fails when run without the fix commit.

Question: if this gets merged, would it also be acceptable for me to make an attempt at updating the preProcess and postProcess docs to mention that they support promises?

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[sidvishnoi]

Thank you @kfranqueiro for filing the detailed bug report and sending this PR.

In general, the idea is correct (and wanted), except there's one problem: Each plugin (including preProcess, postProcess) in ReSpec has a timeout (15 seconds per plugin).
Assume there are 4 functions, each taking 5 seconds. We'll hit that timeout when running in serial. With Promise.all, that timeout won't be triggered in general.

A possible way will be to increase timeout of preProcess/postProcess functions, as an exception.
Another way I experimented in #3320 was to add each "plugin" (in this case, each preProcess/postProcess function) to the top-level plugins list on load. Then each preProcess/postProcess function will be treated as a plugin in itself, use 15s timeout, and run in serial.

[kfranqueiro]

Thanks for the additional context. I take it #3320 never gained traction...

I was certainly a bit wary in terms of how much changing this might extend the time of pre- and post-process, depending on what's been done with them in various configurations. I almost wondered if I should somehow make this behavior optional, even if it is intended to align with current documentation and historical expectations for sync functions.

On the subject of making things optional, I also wonder if it'd be reasonable to make the timeouts for pre- and post-process in particular customizable. e.g., optionally support the following:

preProcess: {
  functions: [/* the usual goes here */],
  timeout: 30000
}

(If I were to make the fix itself optional it could be exposed similarly, via something like sequentialAsync.)

RE potentially extending the hard-coded timeout (either as an exception or across the board), I'm curious what motivated the timeouts, e.g. what plugins had a history of taking too long, and for what kinds of reasons? (I'm assuming network timeouts could be a common one.)

(I suppose another option could be to expose the 15000 via e.g. config.pluginTimeout.)

[marcoscaceres]

@sidvishnoi, I don't think we should block on the timing issue... we should figure out some other way of dealing with it as issues come up.

[Copilot]

Pull Request Overview

This PR fixes the execution order of pre-process and post-process functions to ensure they run sequentially rather than concurrently. The changes address issue #4961 by replacing the parallel execution pattern with sequential execution.

• Replaces Promise.all() with for...of loops to execute async functions in order
• Updates tests to verify both functionality and execution order
• Adds a shared counter mechanism to track invocation sequence

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
tests/spec/core/pre-process-spec.js	Updates existing tests to use toContain and adds new test verifying execution order
tests/spec/core/pre-process-spec.html	Introduces counter mechanism and updates functions to track execution order
src/core/pre-process.js	Replaces parallel execution with sequential for...of loop
src/core/post-process.js	Replaces parallel execution with sequential for...of loop