add a new test case in github actions where we explicitly test with the github dev version of mlr3

Author: MalteKurz

.github/workflows/rcheck.yml

@@ -22,10 +22,11 @@ jobs:
       fail-fast: false
       matrix:
         config:
-          - {os: windows-latest, r: 'release'}
-          - {os: macOS-latest, r: 'release'}
-          - {os: ubuntu-20.04, r: 'release', rspm: "https://packagemanager.rstudio.com/cran/__linux__/focal/latest"}
-          - {os: ubuntu-20.04, r: 'devel', rspm: "https://packagemanager.rstudio.com/cran/__linux__/focal/latest"}
+          - {os: windows-latest, r: 'release', mlr3: 'release'}
+          - {os: macOS-latest, r: 'release', mlr3: 'release'}
+          - {os: ubuntu-20.04, r: 'release', mlr3: 'release', rspm: "https://packagemanager.rstudio.com/cran/__linux__/focal/latest"}
+          - {os: ubuntu-20.04, r: 'devel', mlr3: 'release', rspm: "https://packagemanager.rstudio.com/cran/__linux__/focal/latest"}
+          - {os: ubuntu-20.04, r: 'devel', mlr3: 'dev', rspm: "https://packagemanager.rstudio.com/cran/__linux__/focal/latest"}
 
     env:
       R_REMOTES_NO_ERRORS_FROM_WARNINGS: true
@@ -72,6 +73,12 @@ jobs:
           remotes::install_cran("rcmdcheck")
         shell: Rscript {0}
 
+      - name: mlr3 dev version
+        if: runner.mlr3 == 'dev'
+        run: |
+          remotes::install_github("mlr-org/mlr3")
+        shell: Rscript {0}
+
       - name: Check
         if: runner.os != 'macOS'
         env: