Should setnames() produce duplicate column names without warning?

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
25/100
Issue type
Feature
Clarity
Needs clarification
Activity status
Stale
Tech stack
r
Domain
data

Research direction

Start by reproducing the setnames() calls shown in the issue and observing the duplicate-name and warning behavior. Read the linked November 2013 discussion to understand the unresolved alternatives; done requires an agreed behavior for duplicate column names and a way to verify that decision.

Written by the indexing model from the issue text.

Description

feature request 
IRIS  <- as.data.table(iris)
setnames(IRIS, "Petal.Length", "Sepal.Length") # No warning (but maybe there should be?)
IRIS[, Sepal.Length] # Only first occurrence is returned
setnames(IRIS, "Sepal.Length", "abc.Length") #  Warning: Only first occurrence is changed

Has been discussed at length here. Without conclusion?

Dominant language
R
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