build: speed up logic in Travis CI build steps

Author: dougwilson

.travis.yml

@@ -18,18 +18,68 @@ cache:
   directories:
     - node_modules
 before_install:
-  # Skip updating shrinkwrap / lock
-  - "npm config set shrinkwrap false"
+  - |
+    # Setup utility functions
+    function node_version_lt () {
+      [[ "$(v "$TRAVIS_NODE_VERSION")" -lt "$(v "${1}")" ]]
+    }
+    function npm_module_installed () {
+      npm -lsp ls | grep -Fq "$(pwd)/node_modules/${1}:${1}@"
+    }
+    function npm_remove_module_re () {
+      node -e '
+        fs = require("fs");
+        p = JSON.parse(fs.readFileSync("package.json", "utf8"));
+        r = RegExp(process.argv[1]);
+        for (k in p.devDependencies) {
+          if (r.test(k)) delete p.devDependencies[k];
+        }
+        fs.writeFileSync("package.json", JSON.stringify(p, null, 2) + "\n");
+      ' "$@"
+    }
+    function v () {
+      tr '.' '\n' <<< "${1}" \
+        | awk '{ printf "%03d", $0 }' \
+        | sed 's/^0*//'
+    }
+  # Configure npm
+  - |
+    # Skip updating shrinkwrap / lock
+    npm config set shrinkwrap false
   # Setup Node.js version-specific dependencies
-  - "test $TRAVIS_NODE_VERSION != '0.8' || npm rm --save-dev istanbul"
-  - "test $(echo $TRAVIS_NODE_VERSION | cut -d. -f1) -ge 6 || npm rm --save-dev $(grep -E '\"eslint\\S*\"' package.json | cut -d'\"' -f2)"
+  - |
+    # Configure eslint for linting
+    if node_version_lt '6.0'; then npm_remove_module_re '^eslint(-|$)'
+    fi
+  - |
+    # Configure istanbul for coverage
+    if node_version_lt '0.10'; then npm_remove_module_re '^istanbul$'
+    fi
   # Update Node.js modules
-  - "test ! -d node_modules || npm prune"
-  - "test ! -d node_modules || npm rebuild"
+  - |
+    # Prune & rebuild node_modules
+    if [[ -d node_modules ]]; then
+      npm prune
+      npm rebuild
+    fi
+before_scrpt:
+  - |
+    # Contents of node_modules
+    npm -s ls ||:
 script:
-  # Run test script, depending on istanbul install
-  - "test ! -z $(npm -ps ls istanbul) || npm test"
-  - "test   -z $(npm -ps ls istanbul) || npm run-script test-travis"
-  - "test   -z $(npm -ps ls eslint  ) || npm run-script lint"
+  - |
+    # Run test script, depending on istanbul install
+    if npm_module_installed 'istanbul'; then npm run-script test-travis
+    else npm test
+    fi
+  - |
+    # Run linting, if eslint exists
+    if npm_module_installed 'eslint'; then npm run-script lint
+    fi
 after_script:
-  - "test -e ./coverage/lcov.info && npm install coveralls@2 && cat ./coverage/lcov.info | coveralls"
+  - |
+    # Upload coverage to coveralls if exists
+    if [[ -e ./coverage/lcov.info ]]; then
+      npm install --save-dev coveralls@2
+      coveralls < ./coverage/lcov.info
+    fi