fix(pipelines): graphnode dependencies can have duplicates

[kaizencc]

GraphNode.allDeps allows duplicate dependencies to be returned. This does not have any affect on the performance of the pipelines module, but looks ugly. This was noticed in cdklabs/cdk-pipelines-github#67, where the dependencies are written out to the deploy.yaml file.

I did not change the underlying GraphNode.dependencies structure to be a set (although I think it should) because I feel like that is a breaking change. So instead I've preserved the structure of the API and deduplicated the list of GraphNodes.

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[gitpod-io]

[rix0rrr]

approved but consider simplifying a little

[rix0rrr]

While this isn't wrong, it feels overly complex in this case.

Why don't we use the built-in Set ?

function deduplicateDependencies<A>(dependencies: GraphNode<A>[]) {
  const ret = new Array<GraphNode<A>>();
  const seen = new Set<GraphNode<A>>();

  for (const dep of dependencies) {
    if (seen.has(dep)) { continue; }
    seen.add(dep);
    ret.push(dep);
  }

  return ret;
}

Or if you want to be fancy, with a generator helper function (to save the accumulator variable ret):

function deduplicateDependencies<A>(dependencies: GraphNode<A>[]) {
  const seen = new Set<GraphNode<A>>();
  return Array.from(generate());
 
  function* generate() {
    for (const dep of dependencies) {
      if (seen.has(dep)) { continue; }
      seen.add(dep);
      yield dep;
      ret.push(dep);
    }
  }
}

[rix0rrr]

Even better what you said:

return Array.from(new Set(dependencies));

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