Improve ExtRef identity function

[danyill]

Describe the bug

Currently the ExtRef identity function is not stable for the case of:

• An ExtRef is specified for later binding with an internal address
• A subscription is made

If an IED has an ExtRef and an internal address and the user then does a subscription, then the identity is changed.

open-scd/src/foundation.ts

Lines 824 to 872 in e1b9568

	function extRefIdentity(e: Element): string | number {
	if (!e.parentElement) return NaN;
	const parentIdentity = identity(e.parentElement);
	const iedName = e.getAttribute('iedName');
	const intAddr = e.getAttribute('intAddr');
	const intAddrIndex = Array.from(
	e.parentElement.querySelectorAll(`ExtRef[intAddr="${intAddr}"]`)
	).indexOf(e);
	if (!iedName) return `${parentIdentity}>${intAddr}[${intAddrIndex}]`;
	const [
	ldInst,
	prefix,
	lnClass,
	lnInst,
	doName,
	daName,
	serviceType,
	srcLDInst,
	srcPrefix,
	srcLNClass,
	srcLNInst,
	srcCBName,
	] = [
	'ldInst',
	'prefix',
	'lnClass',
	'lnInst',
	'doName',
	'daName',
	'serviceType',
	'srcLDInst',
	'srcPrefix',
	'srcLNClass',
	'srcLNInst',
	'srcCBName',
	].map(name => e.getAttribute(name));
	const cbPath = srcCBName
	? `${serviceType}:${srcCBName} ${srcLDInst ?? ''}/${srcPrefix ?? ''} ${
	srcLNClass ?? ''
	} ${srcLNInst ?? ''}`
	: '';
	const dataPath = `${iedName} ${ldInst}/${prefix ?? ''} ${lnClass} ${
	lnInst ?? ''
	} ${doName} ${daName ? daName : ''}`;
	return `${parentIdentity}>${cbPath ? cbPath + ' ' : ''}${dataPath}${
	intAddr ? '@' + `${intAddr}` : ''
	}`;
	}

The identity function should return a stable reference.

If an internal address is specified, I think this should be the "primary key". It is also true that tne intAddr can be mapped multiple times but we already use the instance number to take this into account.

Expected behavior

@ca-d and I discussed, and tentatively propose:

function extRefIdentity(e: Element): string | number {
  if (!e.parentElement) return NaN;
  const parentIdentity = identity(e.parentElement);
  const iedName = e.getAttribute('iedName');
  const intAddr = e.getAttribute('intAddr');
  const intAddrIndex = Array.from(
    e.parentElement.querySelectorAll(`ExtRef[intAddr="${intAddr}"]`)
  ).indexOf(e);
-  if (!iedName) return `${parentIdentity}>${intAddr}[${intAddrIndex}]`;
+  if (intAddr) return `${parentIdentity}>${intAddr}[${intAddrIndex}]`;
  const [
    ldInst,
    prefix,
    lnClass,
    lnInst,
    doName,
    daName,
    serviceType,
    srcLDInst,
    srcPrefix,
    srcLNClass,
    srcLNInst,
    srcCBName,
  ] = [
    'ldInst',
    'prefix',
    'lnClass',
    'lnInst',
    'doName',
    'daName',
    'serviceType',
    'srcLDInst',
    'srcPrefix',
    'srcLNClass',
    'srcLNInst',
    'srcCBName',
  ].map(name => e.getAttribute(name));

  const cbPath = srcCBName
    ? `${serviceType}:${srcCBName} ${srcLDInst ?? ''}/${srcPrefix ?? ''} ${
        srcLNClass ?? ''
      } ${srcLNInst ?? ''}`
    : '';
  const dataPath = `${iedName} ${ldInst}/${prefix ?? ''} ${lnClass} ${
    lnInst ?? ''
  } ${doName} ${daName ? daName : ''}`;
  return `${parentIdentity}>${cbPath ? cbPath + ' ' : ''}${dataPath}${
    intAddr ? '@' + `${intAddr}` : ''
  }`;
}

[danyill]

Cases to cover:

1. intAddr there or not there
2. Subscription there or not there.

But this seems OK we said at refinement...