microsoft / microsoft/TypeScript

Detect duplicate nodes during printing

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#18,978 1 comment 1 reaction 0 assignees View on GitHub

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Experience Enhancement Suggestion
Dominant language
Go
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Avg merge
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Merged PRs (30d)
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Description

While rewriting code for refactorings and code fixes, it is quite easy to inadvertently insert a single Node into multiple positions in the tree (i.e. when it should have been cloned). It would be very helpful if the printer (or other, more appropriate, component) detected this, rather than behaving subtly incorrectly or throwing an (apparently) unrelated exception.

One way to do this would be to clear __pos and __end before traversing the tree and then throwing if they are set a second time during the traversal.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by tracing the printer's tree traversal and the Node __pos and __end fields mentioned in the issue. Determine where duplicate node insertion can be detected, then verify that repeated use of the same node produces a clear failure instead of subtle output or an unrelated exception.

Written by the indexing model from the issue text.

Assessment

Tech stack
typescript
Domain
compilers
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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