Skip installing the IDE if it's already installed

The script needs to be informed of the IDE versions that are available even if the user already has them installed or has used an alternate installation method. This change allows install_ide to be used for that purpose.

Author: per1234

Diff for: README.md

@@ -52,7 +52,7 @@ Turn on/off checking for errors with libraries that don't affect sketch verifica
 
 ##### `install_ide [IDEversionList]`
 Install a list of version(s) of the Arduino IDE.
-- Parameter(optional): **IDEversionList** - A list of the versions of the Arduino IDE you want installed, in order from oldest to newest. e.g. `'("1.6.5-r5" "1.6.9" "1.8.2")'`. If no arguments are supplied all IDE versions will be installed. I have defined all versions of the Arduino IDE that have a command line interface in the script for the sake of being complete but I really don't see much reason for testing with the 1.5.x versions of the Arduino IDE. Please only install the IDE versions you actually need for your test to avoid wasting Arduino's bandwidth. This will also result in the builds running faster.
+- Parameter(optional): **IDEversionList** - A list of the versions of the Arduino IDE you want installed, in order from oldest to newest. e.g. `'("1.6.5-r5" "1.6.9" "1.8.2")'`. If no arguments are supplied all IDE versions will be installed. I have defined all versions of the Arduino IDE that have a command line interface in the script for the sake of being complete but I really don't see much reason for testing with the 1.5.x versions of the Arduino IDE. Please only install the IDE versions you actually need for your test to avoid wasting Arduino's bandwidth. This will also result in the builds running faster. Installation of the IDE will be skipped if it's found to already be installed in the folder specified via the `set_application_folder` function so `install_ide` can also be used simply to inform the script which IDE versions are available.
 
 ##### `install_ide startIDEversion [endIDEversion]`
 Install a range of version(s) of the Arduino IDE.

Diff for: arduino-ci-script.sh

@@ -246,30 +246,36 @@ function install_ide()
   eval "$INSTALLED_IDE_VERSION_LIST_ARRAY"
   local IDEversion
   for IDEversion in "${IDEversionListArray[@]}"; do
-    if [[ "$ARDUINO_CI_SCRIPT_VERBOSITY_LEVEL" -eq 0 ]]; then
-      # If the download/installation process is going slowly when installing a lot of IDE versions this function may cause the build to fail due to exceeding Travis CI's 10 minutes without log output timeout so it's necessary to periodically print something.
-      echo "Installing: $IDEversion"
-    fi
-    # Determine download file extension
-    local tgzExtensionVersionsRegex="1.5.[0-9]"
-    if [[ "$IDEversion" =~ $tgzExtensionVersionsRegex ]]; then
-      # The download file extension prior to 1.6.0 is .tgz
-      local downloadFileExtension="tgz"
-    else
-      local downloadFileExtension="tar.xz"
-    fi
+    local IDEinstallFolder="$ARDUINO_CI_SCRIPT_APPLICATION_FOLDER/arduino-${IDEversion}"
 
-    if [[ "$IDEversion" == "hourly" ]]; then
-      # Deal with the inaccurate name given to the hourly build download
-      local downloadVersion="nightly"
-    else
-      local downloadVersion="$IDEversion"
-    fi
+    # Don't unnecessarily install the IDE
+    if ! [[ -d "$IDEinstallFolder" ]]; then
+      if [[ "$ARDUINO_CI_SCRIPT_VERBOSITY_LEVEL" -eq 0 ]]; then
+        # If the download/installation process is going slowly when installing a lot of IDE versions this function may cause the build to fail due to exceeding Travis CI's 10 minutes without log output timeout so it's necessary to periodically print something.
+        echo "Installing: $IDEversion"
+      fi
 
-    wget --no-verbose $ARDUINO_CI_SCRIPT_QUIET_OPTION "http://downloads.arduino.cc/arduino-${downloadVersion}-linux64.${downloadFileExtension}"
-    tar --extract --file="arduino-${downloadVersion}-linux64.${downloadFileExtension}"
-    rm $ARDUINO_CI_SCRIPT_VERBOSITY_OPTION "arduino-${downloadVersion}-linux64.${downloadFileExtension}"
-    mv $ARDUINO_CI_SCRIPT_VERBOSITY_OPTION "arduino-${downloadVersion}" "$ARDUINO_CI_SCRIPT_APPLICATION_FOLDER/arduino-${IDEversion}"
+      # Determine download file extension
+      local tgzExtensionVersionsRegex="1.5.[0-9]"
+      if [[ "$IDEversion" =~ $tgzExtensionVersionsRegex ]]; then
+        # The download file extension prior to 1.6.0 is .tgz
+        local downloadFileExtension="tgz"
+      else
+        local downloadFileExtension="tar.xz"
+      fi
+
+      if [[ "$IDEversion" == "hourly" ]]; then
+        # Deal with the inaccurate name given to the hourly build download
+        local downloadVersion="nightly"
+      else
+        local downloadVersion="$IDEversion"
+      fi
+
+      wget --no-verbose $ARDUINO_CI_SCRIPT_QUIET_OPTION "http://downloads.arduino.cc/arduino-${downloadVersion}-linux64.${downloadFileExtension}"
+      tar --extract --file="arduino-${downloadVersion}-linux64.${downloadFileExtension}"
+      rm $ARDUINO_CI_SCRIPT_VERBOSITY_OPTION "arduino-${downloadVersion}-linux64.${downloadFileExtension}"
+      mv $ARDUINO_CI_SCRIPT_VERBOSITY_OPTION "arduino-${downloadVersion}" "$IDEinstallFolder"
+    fi
   done
 
   set_ide_preference "compiler.warning_level=all"