Restructure highlighter server handling

In particular, this only attempts to install and start the server if local Wattsi is in use. As part of this, we no longer check for the existence and version of Wattsi each time before we invoke it, but instead only once.

Author: domenic

build.sh

@@ -41,14 +41,13 @@ HIGHLIGHT_SERVER_URL="http://127.0.0.1:8080" # this needs to be coordinated with
 function main {
   processCommandLineArgs "$@"
 
+  checkWattsi
+  ensureHighlighterInstalled
+
   # $SKIP_BUILD_UPDATE_CHECK is set inside the Dockerfile so that we don't check for updates both inside and outside
   # the Docker container.
   if [[ $DO_UPDATE == "true" && $SKIP_BUILD_UPDATE_CHECK != "true" ]]; then
     checkHTMLBuildIsUpToDate
-    # If we're using Docker then this will be installed inside the container.
-    if [[ $USE_DOCKER != "true" ]]; then
-      pip3 install bs-highlighter
-    fi
   fi
 
   findHTMLSource
@@ -178,6 +177,24 @@ function checkHTMLBuildIsUpToDate {
   fi
 }
 
+# Tries to install the bs-highlighter Python package if necessary
+# - Arguments: none
+# - Output:
+#   - Either bs-highlighter-server will be in the $PATH, or a warning will be echoed
+function ensureHighlighterInstalled {
+  # If we're using Docker then this will be installed inside the container.
+  # If we're not using local Wattsi then we won't use the local highlighter.
+  if [[ $USE_DOCKER != "true" && $LOCAL_WATTSI == "true" ]]; then
+    if hash pip3 2>/dev/null; then
+      if ! hash bs-highlighter-server 2>/dev/null; then
+        pip3 install bs-highlighter
+      fi
+    else
+      LOCAL_WATTSI="false"
+    fi
+  fi
+}
+
 # Finds the location of the HTML Standard, and stores it in the HTML_SOURCE variable.
 # It either guesses based on directory structure, or interactively prompts the user.
 # - Arguments: none
@@ -537,6 +554,25 @@ Disallow: /review-drafts/" > "$HTML_OUTPUT/robots.txt"
   fi
 }
 
+# Checks if Wattsi is available and up to date
+# - Arguments: none
+# - Output:
+#   - Sets $LOCAL_WATTSI to true or false
+#   - Echoes a warning if Wattsi is out of date according to $WATTSI_LATEST
+function checkWattsi {
+  if hash wattsi 2>/dev/null; then
+    if [[ "$(wattsi --version | cut -d' ' -f2)" -lt "$WATTSI_LATEST" ]]; then
+      echo
+      echo "Warning: Your wattsi version is out of date. You should to rebuild an"
+      echo "up-to-date wattsi binary from the wattsi sources."
+      echo
+    fi
+    LOCAL_WATTSI=true
+  else
+    LOCAL_WATTSI=false
+  fi
+}
+
 # Runs Wattsi on the given file, either locally or using the web service
 # - Arguments:
 #   - $1: the file to run Wattsi on
@@ -547,7 +583,6 @@ Disallow: /review-drafts/" > "$HTML_OUTPUT/robots.txt"
 #   - $HTML_TEMP/wattsi-output directory will contain the output from Wattsi on success
 #   - $HTML_TEMP/wattsi-output.txt will contain the output from Wattsi, on both success and failure
 function runWattsi {
-
   rm -rf "$2"
   mkdir "$2"
 
@@ -559,19 +594,12 @@ function runWattsi {
     "$HTML_CACHE/caniuse.json" \
     "$HTML_CACHE/mdn-spec-links-html.json" \
     "$HIGHLIGHT_SERVER_URL" )
-  if hash wattsi 2>/dev/null; then
-    if [[ "$(wattsi --version | cut -d' ' -f2)" -lt "$WATTSI_LATEST" ]]; then
-      echo
-      echo "Warning: Your wattsi version is out of date. You should to rebuild an"
-      echo "up-to-date wattsi binary from the wattsi sources."
-      echo
-    fi
+  if [[ "$LOCAL_WATTSI" == "true" ]]; then
     WATTSI_RESULT="0"
     wattsi "${WATTSI_ARGS[@]}" || WATTSI_RESULT=$?
   else
-    LOCAL_WATTSI=false
     $QUIET || echo
-    $QUIET || echo "Local wattsi is not present; trying the build server..."
+    $QUIET || echo "Local wattsi or pip3 are not present; trying the build server..."
 
     CURL_ARGS=( https://build.whatwg.org/wattsi \
                 --form "source=@$1" \
@@ -624,19 +652,20 @@ function generateBacklinks {
   perl .post-process-partial-backlink-generator.pl "$HTML_TEMP/wattsi-output/index-$1" > "$2/index.html";
 }
 
-# Starts the syntax-highlighting Python server
+# Starts the syntax-highlighting Python server, when appropriate
 # Arguments: none
-# Output:
+# Output: if the server is necessary, then
 # - A server will be running in the background, at $HIGHLIGHT_SERVER_URL
 # - $HIGHLIGHT_SERVER_PID will be set for later use by stopHighlightServer
 function startHighlightServer {
-  HIGHLIGHT_SERVER_ARGS=()
-  $QUIET && HIGHLIGHT_SERVER_ARGS+=( --quiet )
-  # shellcheck disable=SC2068
-  bs-highlighter-server ${HIGHLIGHT_SERVER_ARGS[@]+"${HIGHLIGHT_SERVER_ARGS[@]}"} &
-  HIGHLIGHT_SERVER_PID=$!
+  if [[ "$LOCAL_WATTSI" == "true" ]]; then
+    HIGHLIGHT_SERVER_ARGS=()
+    $QUIET && HIGHLIGHT_SERVER_ARGS+=( --quiet )
+    bs-highlighter-server ${HIGHLIGHT_SERVER_ARGS[@]+"${HIGHLIGHT_SERVER_ARGS[@]}"} &
+    HIGHLIGHT_SERVER_PID=$!
 
-  trap stopHighlightServer EXIT
+    trap stopHighlightServer EXIT
+  fi
 }
 
 # Stops the syntax-highlighting Python server