tests/knitr.R mismatch

[jangorecki]

reported on CRAN now. https://cran.r-project.org/web/checks/check_results_data.table.html
none of the commits mentioned in 1.16.2 issue seems to be providing the fix, so likely the issue is still there (fyi @TysonStanley )

    Comparing ‘knitr.Rout’ to ‘knitr.Rout.save’ ...28,38d27
  < ```
  < 
  < ```
  < ##        x     y     z
  < ##    <int> <int> <int>
  < ## 1:     1     4     7
  < ## 2:     2     5     8
  < ## 3:     3     6     9
  < ```
  < 
  < ``` r
  52,62d40
  < ```
  < 
  < ```
  < ##        x     y     z     a
  < ##    <int> <int> <int> <int>
  < ## 1:     1     4    10     1
  < ## 2:     2     5    11     1
  < ## 3:     3     6    12     1
  < ```
  < 
  < ``` r

[MichaelChirico]

Copying @TysonStanley 's comment here:

Looks like the difference is that DT[, z := 7:9] is printing in the knitr output.

  < ##        x     y     z
  < ##    <int> <int> <int>
  < ## 1:     1     4     7
  < ## 2:     2     5     8
  < ## 3:     3     6     9

[MichaelChirico]

Copying Tyson's next comment here too:

Not sure why it's not showing up in CI checks at all. It's a note on Linux and windows on CRAN and it showed up on MacOS for me here.

[MichaelChirico]

I'm not reproducing it locally, and we don't see it on GHA nor on GitLab CI logs. Makes it a lot tougher to debug.

@TysonStanley, can you confirm your R, knitr and data.table versions where you're seeing the issue? And maybe try doing trace(data.table:::shouldPrint, at=3, quote(message("ret=", ret))) and check the output of the knitr test again?

[TysonStanley]

Only happens when I'm accessing R directly in the terminal but this is what happened when I inserted that code into the .Rmd before knitting:

``` r
require(data.table)              # print?
trace(data.table:::shouldPrint, at=3, quote(message("ret=", ret)))
```

```
## [1] "shouldPrint"
```

``` r
DT = data.table(x=1:3, y=4:6)    # no
DT                               # yes
```

```
## Tracing shouldPrint(x) step 3
```

```
##        x     y
##    <int> <int>
## 1:     1     4
## 2:     2     5
## 3:     3     6
```

``` r
DT[, z := 7:9]                   # no
```

```
## Tracing shouldPrint(x) step 3
```

```
##        x     y     z
##    <int> <int> <int>
## 1:     1     4     7
## 2:     2     5     8
## 3:     3     6     9
```

``` r
print(DT[, z := 10:12])          # yes
```

```
## Tracing shouldPrint(x) step 3
```

```
##        x     y     z
##    <int> <int> <int>
## 1:     1     4    10
## 2:     2     5    11
## 3:     3     6    12
```

``` r
if (1 < 2) DT[, a := 1L]         # no
```

```
## Tracing shouldPrint(x) step 3
```

```
##        x     y     z     a
##    <int> <int> <int> <int>
## 1:     1     4    10     1
## 2:     2     5    11     1
## 3:     3     6    12     1
```

``` r
DT                               # yes
```

```
## Tracing shouldPrint(x) step 3
```

```
##        x     y     z     a
##    <int> <int> <int> <int>
## 1:     1     4    10     1
## 2:     2     5    11     1
## 3:     3     6    12     1
```
Some text.

The DT[, z := 10:12] definitely triggers shouldPrint(x). Is there more information I can extract? Should I set verbose = TRUE for these as well?