feat(7614): added redirection of data.frame at dcast and melt to dcast.data.table and melt.data.table

[manmita]

Closes #7614

I added tests for data.frame to check if dcast and melt work directly but got the following error

Running test id 2365.1         Test 2365.1 produced 1 errors but expected 0
Expected: 
Observed: no applicable method for 'melt' applied to an object of class "data.frame"
Running test id 2365.2         Test 2365.2 produced 1 errors but expected 0
Expected: 
Observed: no applicable method for 'dcast' applied to an object of class "data.frame"

Hence redirected data.frame to dcast.data.table directly similarly for melt

[github-actions]

• HEAD=fix/dcast_melt_for_data.frame stopped early for DT[by,verbose=TRUE] improved in #6296
• HEAD=fix/dcast_melt_for_data.frame stopped early for DT[,.SD] improved in #4501
  

Generated via commit a05b069

Download link for the artifact containing the test results: ↓ atime-results.zip

Task	Duration
R setup and installing dependencies	2 minutes and 51 seconds
Installing different package versions	23 seconds
Running and plotting the test cases	4 minutes and 5 seconds

[MichaelChirico]

Just remove the error in dcast.data.table. Don't coerce.

[manmita]

got it

[MichaelChirico]

I think this constitutes a breaking change for packages/scripts using both {data.table} and {reshape2} (e.g. {WebAnalytics} or {BTSPAS}), which might result in the wrong S3 method being invoked.

Please investigate the interaction of your update with {reshape2}, e.g. the load order.

I think the solution is not to have a data.frame method, but to fake one in the dcast() generic like:

dcast = function(x, ...) {
  if (!is.data.table(x) && is.data.frame(x)) return(dcast.data.table(x, ...))
  UseMethod("dcast")
}

[manmita]

have redirected data.frame to the dcast.data.table
currently fixing a few errors

Running test id 2365.2         Test 2365.2 produced 1 errors but expected 0
Expected: 
Observed: argument "formula" is missing, with no default
Test 2365.2 produced 1 messages but expected 0
Expected: 
Observed: Using 'v' as value column. Use 'value.var' to override

Will update the PR once this is fixed

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 99.01%. Comparing base (b537ec4) to head (6502e86).
⚠️ Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
R/fcast.R	66.66%	1 Missing ⚠️
R/fmelt.R	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7634      +/-   ##
==========================================
- Coverage   99.02%   99.01%   -0.02%     
==========================================
  Files          87       87              
  Lines       16890    16896       +6     
==========================================
+ Hits        16726    16730       +4     
- Misses        164      166       +2     

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[manmita]

Hii @MichaelChirico without coercing it is failing the following test

df_dcast = data.frame(a = c("x", "y"), b = 1:2, v = 3:4)
dt_dcast = data.table(a = c("x", "y"), b = 1:2, v = 3:4)
test(2365.2, dcast(df_dcast, a ~ b, value.var = "v"), dcast(dt_dcast, a ~ b, value.var = "v"))

error: object of type 'symbol' is not subsettable

prolly due to fast subsetting in data tables which isnt present in data frames?
Will need to test out the point of crash (using gdb) - will check it out tomorrow ^^