Make file distribution optional and better error message

[robinhasse]

• getfiledestination now returns NULL if no files file is found
  • Before, it threw a meaningless error message.
• download_distribute can now handle a NULL from getfiledestination and will download and unpack but not distribute in this case
  • It gives a message to let the user know that there is no distribution of files.
• This allows to use the function also when no distribution is wanted (like in BRICK, potentially EDGE-T).

[codecov[bot]]

Codecov Report

Attention: 37 lines in your changes are missing coverage. Please review.

Comparison is base (f88533c) 34.96% compared to head (83c1f42) 34.71%.

:exclamation: Current head 83c1f42 differs from pull request most recent head 208905b. Consider uploading reports for the commit 208905b to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #72 +/- ## ========================================== - Coverage 34.96% 34.71% -0.25% ========================================== Files 51 51 Lines 1676 1688 +12 ========================================== Hits 586 586 - Misses 1090 1102 +12 ``` | [Files](https://app.codecov.io/gh/pik-piam/gms/pull/72?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pik-piam) | Coverage Δ | | |---|---|---| | [R/getfiledestinations.R](https://app.codecov.io/gh/pik-piam/gms/pull/72?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pik-piam#diff-Ui9nZXRmaWxlZGVzdGluYXRpb25zLlI=) | `0.00% <0.00%> (ø)` | | | [R/download\_distribute.R](https://app.codecov.io/gh/pik-piam/gms/pull/72?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pik-piam#diff-Ui9kb3dubG9hZF9kaXN0cmlidXRlLlI=) | `0.00% <0.00%> (ø)` | |

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[orichters]

Wouldn't the alternative simply be to return NULL here in getfiledestinations() and then make the distribution conditional on ! is.null(file2destination)? So if you don't find input files, don't distribute anything? You would not need the additional distribute switch anymore…

[robinhasse]

Wouldn't the alternative simply be to return NULL here in getfiledestinations() and then make the distribution conditional on ! is.null(file2destination)? So if you don't find input files, don't distribute anything?

Thats definitely smarter but changes the default behaviour (though only in case of a former error). I could add a warning that can be suppressed if you don't expect distribution.

[orichters]

I even think a message would be sufficient. If you would like to use the function as such in your model, then it shouldn't raise a warning.

[robinhasse]

I even think a message would be sufficient. If you would like to use the function as such in your model, then it shouldn't raise a warning.

I eventually did it the way you suggested. Thanks Oli!

[robinhasse]

I like the idea of the PR, it just needs some more finetuning (see my specific comments)

Thanks @tscheypidi for taking a look. You mentioned (multiple?) comments but I see just one. Do you have other concerns I should take care of?

[tscheypidi]

I made two comments, but was now also not able to see my second one. I was adding to Olivers comment with the messaging the suggestion not to trigger a message at all if not files are to be deleted, as this might be confusing to users not familiar with the function and is probably not necessary to be mentioned. Other than that I think I did not had any further comments