*/
    void attachArtifact(@Nonnull Project project, @Nonnull ProducedArtifact artifact, @Nonnull Path path);

    /**
     * {@return all source root directories}, including the disabled ones, for all languages and scopes.
     * For listing only the {@linkplain SourceRoot#enabled() enabled} source roots,
     * the following code can be used:
     *
     * <pre>{@literal

	// stop the replay go-routine.
	if h.store != nil {
		h.storeCtxCancel()
	}

	// Set logch to nil and close it.
	// This will block all Send operations,
	// and finish the existing ones.
	// All future ones will be discarded.
	h.logChMu.Lock()
	xioutil.SafeClose(h.logCh)
	h.logCh = nil
	h.logChMu.Unlock()

	if h.producer != nil {
		h.producer.Close()
		h.client.Close()
	}

#### Operation { #operation }

"Operation" here refers to one of the HTTP "methods".

One of:

* `POST`
* `GET`
* `PUT`
* `DELETE`

...and the more exotic ones:

* `OPTIONS`
* `HEAD`
* `PATCH`
* `TRACE`

In the HTTP protocol, you can communicate to each path using one (or more) of these "methods".

---

   * with underutilization, then we want stored permits to be given out /faster/ than fresh ones,
   * because underutilization = free resources for the taking. If we are primarily interested to
   * deal with overflow, then stored permits could be given out /slower/ than fresh ones. Thus, we
   * require a (different in each case) function that translates storedPermits to throttling time.
   *

 * </ul>
 * In addition to these, there will be a fifth one when a minor reaches feature freeze, we call this the <i>staged</i>
 * version:
 * <ul>
 * <li>the unreleased <b>staged</b>, M.N-2.0 (N &gt; 2) on the `M.(N-2)` branch</li>
 * </ul>
 * <p>
 * Each build is only concerned with versions before it, as those are the ones that need to be tested

	h.storeCtxCancel()

	// Wait for messages to be sent...
	h.wg.Wait()

	// Set logch to nil and close it.
	// This will block all Send operations,
	// and finish the existing ones.
	// All future ones will be discarded.
	h.logChMu.Lock()
	xioutil.SafeClose(h.logCh)
	h.logCh = nil
	h.logChMu.Unlock()

- asking to use a plugin for which you do not have a version defined - tools to easily select versions
- goal not found in a plugin (probably could list the ones that are)

 */

// PluginNotFoundException, PluginResolutionException, PluginDescriptorParsingException,
// CycleDetectedInPluginGraphException;

/**
 * Transform an exception into useful end-user message.
 */

  /**
   * When we need a new thread to run tasks, we call [Backend.execute]. A few microseconds later we
   * expect a newly-started thread to call [Runnable.run]. We shouldn't request new threads until
   * the already-requested ones are in service, otherwise we might create more threads than we need.
   *
   * We use [executeCallCount] and [runCallCount] to defend against starting more threads than we
   * need. Both fields are guarded by `this`.
   */

    for (Future<?> result : results) {
      if (!result.isCancelled()) {
        result.get(10, SECONDS);
      }
      // TODO(cpovirk): Verify that the cancelled futures are exactly ones that we expect.
    }

    assertThat(logHandler.getStoredLogRecords()).isEmpty();
  }

  public void testAvoidsStackOverflow_manySubmitted() throws Exception {

// in the tests.
func isSpace(r rune) bool {
	if r <= '\u00FF' {
		// Obvious ASCII ones: \t through \r plus space. Plus two Latin-1 oddballs.
		switch r {
		case ' ', '\t', '\n', '\v', '\f', '\r':
			return true
		case '\u0085', '\u00A0':
			return true
		}
		return false
	}
	// High-valued ones.
	if '\u2000' <= r && r <= '\u200a' {
		return true
	}
	switch r {