New checks for Java version against Maven files.

third_party/closure_compiler/roll_closure_compiler

 #!/bin/bash
 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # Download the newest version of Closure Compiler, build it and put into Chrome
 # source tree. Also update externs/chrome_extensions.js.
 #
 # TODO(dbeam): we don't really need to build the compiler any more. We used to
 # need to because we built a custom runner. We could probably just curl
 # https://dl.google.com/closure-compiler/compiler-latest.zip and unzip. And get
 # the externs from rawgit.com.
 
-java -version 2>&1 | head -1 | egrep -q '\b1\.7'
-if [[ $? -ne 0 ]]; then
-  echo "This script requires Java 1.7" >&2
-  exit 1
-fi
-
-javac -version 2>&1 | egrep -q '\b1\.7'
-if [[ $? -ne 0 ]]; then
-  echo "This script requires JDK 1.7" >&2
-  exit 1
-fi
-
 readonly SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 readonly TEMP_DIR=$(mktemp -d)
 readonly EXTERNS_DIR="${SCRIPT_DIR}/externs"
 readonly README="${SCRIPT_DIR}/README.chromium"
 
 cleanup() {
   rm -rf "${TEMP_DIR}"
 }
 
 get_sha1() {
@@ skipping 20 matching lines @@
   cleanup
   exit 0
 else
   head_range=$(cat <<EOT
 Change log:
 https://github.com/google/closure-compiler/compare/${old_head}...${new_head}
 EOT
 )
 fi
 
+check_jdk_version() {
+  # Pretty contrived checks modeling how we write Maven XML files.
+  if ! test -r "$2"; then

[Dan Beam, 2017/04/04 17:30:34]

the shell styleguide says something about not using test but i'm too lazy to
look up a better way (maybe [[ ! -r "$2" ]]?).

https://google.github.io/styleguide/shell.xml#Test,_%5B_and_%5B%5B

+    echo "Could not find $2" >&2
+    exit 1
+  elif ! fgrep -q '<jdk.version>'$1'</jdk.version>' "$2"; then
+    echo "JDK version $1 must be specified in $2" >&2
+    exit 1
+  elif ! fgrep -q '<source>${jdk.version}</source>' "$2"; then
+    echo "Java source must be specified to be \${jdk.version} in $2" >&2
+    exit 1
+  elif ! fgrep -q '<target>${jdk.version}</target>' "$2"; then
+    echo "Java target must be specified to be \${jdk.version} in $2" >&2
+    exit 1
+  fi
+}
+
+echo "Checking JDK Version Used to Build"
+check_jdk_version 1.7 pom.xml
+
 echo "Building Closure Compiler"
 mvn clean install -DskipTests=true --projects com.google.javascript:closure-compiler,com.google.javascript:closure-compiler-externs
 
 if [[ "$?" -ne 0 ]]; then
   echo "Failed to build jar, copying nothing" >&2
   cleanup
   exit 1
 fi
 
 # TODO(dbeam): the Maven-built jar seems a little bigger than the ant version.
@@ skipping 59 matching lines @@
 echo "${head_range}"
 if [[ ! -z "${extensions_range}" ]]; then echo "${extensions_range}"; fi
 if [[ ! -z "${polymer_range}" ]]; then echo "${polymer_range}"; fi
 echo
 echo "TBR="
 echo "BUG='"
 echo
 echo "git cl upload"
 
 cleanup