[r-package] cut CI-time dependency on craigcitro/r-travis (fixes #4348)

.travis.yml

@@ -72,6 +72,7 @@ addons:
       - graphviz
       - openssl
       - libgit2
+      - r
     update: true
 
 before_install:

tests/travis/run_test.sh

@@ -79,23 +79,50 @@ fi
 
 if [ ${TASK} == "r_test" ]; then
     set -e
-    export _R_CHECK_TIMINGS_=0
-    export R_BUILD_ARGS="--no-build-vignettes --no-manual"
-    export R_CHECK_ARGS="--no-vignettes --no-manual"
-    if [ ${TRAVIS_OS_NAME} == "osx" ]; then
-        # Work-around to fix "gfortran command not found" error
-        sudo ln -s $(which gfortran-7) /usr/local/bin/gfortran
-        sudo mkdir -p /usr/local/gfortran/lib/gcc/x86_64-apple-darwin15
-        sudo ln -s /usr/local/lib/gcc/7 /usr/local/gfortran/lib/gcc/x86_64-apple-darwin15/6.1.0
-    fi
-
-    curl -OL https://raw.githubusercontent.com/craigcitro/r-travis/master/scripts/travis-tool.sh
-    chmod 755 ./travis-tool.sh
-    ./travis-tool.sh bootstrap
+
     make Rpack
     cd ./xgboost
-    ../travis-tool.sh install_deps
-    ../travis-tool.sh run_tests
+
+    # Install package deps
+    Rscript -e "install.packages( \
+        c('devtools', 'testthat', 'lintr') \
+        , repos = 'http://cloud.r-project.org' \
+        , dependencies = c('Depends', 'Imports', 'LinkingTo') \
+    )"
+
+    Rscript -e \
+        "devtools::install_deps( \
+            repos = 'http://cloud.r-project.org' \
+            , upgrade = 'never' \
+            , dependencies = c('Depends', 'Imports', 'LinkingTo') \
+        )"
+
+    # install suggested packages separately to avoid huge build times
+    Rscript -e "install.packages( \
+        c('DiagrammeR', 'Ckmeans.1d.dp', 'vcd') \
+        , repos = 'https://cloud.r-project.org' \
+        , dependencies = c('Depends', 'Imports', 'LinkingTo') \
+    )"
+
+    # Run tests
+    echo "Building with R CMD build"
+    R CMD build \
+        --no-build-vignettes \
+        --no-manual \
+        .
+
+    echo "Running R tests"
+    R_PACKAGE_TARBALL=$(ls -1t *.tar.gz | head -n 1)
+
+    export _R_CHECK_TIMINGS_=0
+    export _R_CHECK_FORCE_SUGGESTS_=false
+    R CMD check \
+        ${R_PACKAGE_TARBALL} \
+        --no-vignettes \
+        --no-manual \
+        --as-cran \
+        --install-args=--build
+
     exit 0
 fi