java_requirement: port to Linux and refactor

Split the core requirement class into generic, Linux-specific,
and macOS-specific parts.

Additionally, the Linux version is now able to detect Java versions
(the previous Linuxbrew implementation was only able to detect
if Java was present at all.)

Library/Homebrew/extend/os/linux/requirements/java_requirement.rb

@@ -0,0 +1,19 @@
+require "language/java"
+
+class JavaRequirement < Requirement
+  default_formula "jdk"
+
+  env do
+    next unless @java_home
+    env_java_common
+    if (Pathname.new(@java_home)/"include").exist? # Oracle JVM
+      env_oracle_jdk
+    end
+  end
+
+  private
+
+  def oracle_java_os
+    :linux
+  end
+end

Library/Homebrew/extend/os/mac/requirements/java_requirement.rb

@@ -0,0 +1,40 @@
+class JavaRequirement
+  cask "java"
+
+  env do
+    env_java_common
+    java_home = Pathname.new(@java_home)
+    if (java_home/"include").exist? # Oracle JVM
+      env_oracle_jdk
+    else # Apple JVM
+      env_apple
+    end
+  end
+
+  private
+
+  def possible_javas
+    javas = []
+    javas << Pathname.new(ENV["JAVA_HOME"])/"bin/java" if ENV["JAVA_HOME"]
+    javas << java_home_cmd
+    javas << which("java")
+    javas
+  end
+
+  def java_home_cmd
+    return nil unless File.executable?("/usr/libexec/java_home")
+    args = %w[--failfast]
+    args << "--version" << @version.to_s if @version
+    java_home = Utils.popen_read("/usr/libexec/java_home", *args).chomp
+    return nil unless $?.success?
+    Pathname.new(java_home)/"bin/java"
+  end
+
+  def env_apple
+    ENV.append_to_cflags "-I/System/Library/Frameworks/JavaVM.framework/Versions/Current/Headers/"
+  end
+
+  def oracle_java_os
+    :darwin
+  end
+end

Library/Homebrew/extend/os/requirements/java_requirement.rb

@@ -0,0 +1,7 @@
+require "requirements/java_requirement"
+
+if OS.mac?
+  require "extend/os/mac/requirements/java_requirement"
+elsif OS.linux?
+  require "extend/os/linux/requirements/java_requirement"
+end

Library/Homebrew/requirements/java_requirement.rb

@@ -2,28 +2,12 @@ require "language/java"
 
 class JavaRequirement < Requirement
   fatal true
-  cask "java"
   download "http://www.oracle.com/technetwork/java/javase/downloads/index.html"
 
   satisfy build_env: false do
-    next false unless File.executable? "/usr/libexec/java_home"
+    setup_java
-
+    next false unless @java
-    args = %w[--failfast]
+    next true
-    args << "--version" << @version.to_s if @version
-    @java_home = Utils.popen_read("/usr/libexec/java_home", *args).chomp
-    $?.success?
-  end
-
-  env do
-    java_home = Pathname.new(@java_home)
-    ENV["JAVA_HOME"] = java_home
-    ENV.prepend_path "PATH", java_home/"bin"
-    if (java_home/"include").exist? # Oracle JVM
-      ENV.append_to_cflags "-I#{java_home}/include"
-      ENV.append_to_cflags "-I#{java_home}/include/darwin"
-    else # Apple JVM
-      ENV.append_to_cflags "-I/System/Library/Frameworks/JavaVM.framework/Versions/Current/Headers/"
-    end
   end
 
   def initialize(tags)
@@ -45,16 +29,86 @@ class JavaRequirement < Requirement
 
   def display_s
     if @version
-      if @version[-1] == "+"
+      if exact_version?
-        op = ">="
-        version = @version[0, @version.length-1]
-      else
         op = "="
-        version = @version
+      else
+        op = ">="
       end
-      "#{name} #{op} #{version}"
+      "#{name} #{op} #{version_without_plus}"
     else
       name
     end
   end
+
+  private
+
+  def version_without_plus
+    if exact_version?
+      @version
+    else
+      @version[0, @version.length-1]
+    end
+  end
+
+  def exact_version?
+    @version && @version.to_s.chars.last != "+"
+  end
+
+  def setup_java
+    java = preferred_java
+    return unless java
+    @java = java
+    @java_home = java.parent.parent
+  end
+
+  def possible_javas
+    javas = []
+    javas << Pathname.new(ENV["JAVA_HOME"])/"bin/java" if ENV["JAVA_HOME"]
+    jdk = begin
+      Formula["jdk"]
+    rescue FormulaUnavailableError
+      nil
+    end
+    javas << jdk.bin/"java" if jdk && jdk.installed?
+    javas << which("java")
+    javas
+  end
+
+  def preferred_java
+    possible_javas.detect do |java|
+      next false unless java && java.executable?
+      next true unless @version
+      next true if satisfies_version(java)
+    end
+  end
+
+  def env_java_common
+    java_home = Pathname.new(@java_home)
+    ENV["JAVA_HOME"] = java_home
+    ENV.prepend_path "PATH", java_home/"bin"
+  end
+
+  def env_oracle_jdk
+    java_home = Pathname.new(@java_home)
+    ENV.append_to_cflags "-I#{java_home}/include"
+    ENV.append_to_cflags "-I#{java_home}/include/#{oracle_java_os}"
+  end
+
+  def oracle_java_os
+    nil
+  end
+
+  def satisfies_version(java)
+    java_version_s = Utils.popen_read("#{java} -version 2>&1")[/1.\d/]
+    return false unless java_version_s
+    java_version = Version.create(java_version_s)
+    needed_version = Version.create(version_without_plus)
+    if exact_version?
+      java_version == needed_version
+    else
+      java_version >= needed_version
+    end
+  end
 end
+
+require "extend/os/requirements/java_requirement"

Library/Homebrew/test/java_requirement_test.rb

@@ -0,0 +1,50 @@
+require "testing_env"
+require "requirements/java_requirement"
+
+class JavaRequirementTests < Homebrew::TestCase
+  def setup
+    super
+    ENV["JAVA_HOME"] = nil
+  end
+
+  def test_message
+    a = JavaRequirement.new([])
+    assert_match(/Java is required to install this formula./, a.message)
+  end
+
+  def test_inspect
+    a = JavaRequirement.new(%w[1.7+])
+    assert_equal a.inspect, '#<JavaRequirement: "java" [] version="1.7+">'
+  end
+
+  def test_display_s
+    x = JavaRequirement.new([])
+    assert_equal x.display_s, "java"
+    y = JavaRequirement.new(%w[1.8])
+    assert_equal y.display_s, "java = 1.8"
+    z = JavaRequirement.new(%w[1.8+])
+    assert_equal z.display_s, "java >= 1.8"
+  end
+
+  def test_satisfied?
+    a = JavaRequirement.new(%w[1.8])
+    File.stubs(:executable?).returns(false)
+    refute_predicate a, :satisfied?
+
+    b = JavaRequirement.new([])
+    b.stubs(:preferred_java).returns(Pathname.new("/usr/bin/java"))
+    assert_predicate b, :satisfied?
+
+    c = JavaRequirement.new(%w[1.7+])
+    c.stubs(:possible_javas).returns([Pathname.new("/usr/bin/java")])
+    Utils.stubs(:popen_read).returns('java version "1.6.0_5"')
+    refute_predicate c, :satisfied?
+    Utils.stubs(:popen_read).returns('java version "1.8.0_5"')
+    assert_predicate c, :satisfied?
+
+    d = JavaRequirement.new(%w[1.7])
+    d.stubs(:possible_javas).returns([Pathname.new("/usr/bin/java")])
+    Utils.stubs(:popen_read).returns('java version "1.8.0_5"')
+    refute_predicate d, :satisfied?
+  end
+end

Library/Homebrew/test/os/mac/java_requirement_test.rb

@@ -0,0 +1,31 @@
+require "testing_env"
+require "requirements/java_requirement"
+require "fileutils"
+
+class OSMacJavaRequirementTests < Homebrew::TestCase
+  def setup
+    super
+    @java_req = JavaRequirement.new(%w[1.8])
+    @tmp_java_home = mktmpdir
+    @tmp_pathname = Pathname.new(@tmp_java_home)
+    FileUtils.mkdir @tmp_pathname/"bin"
+    FileUtils.touch @tmp_pathname/"bin/java"
+    @java_req.stubs(:preferred_java).returns(@tmp_pathname/"bin/java")
+    @java_req.satisfied?
+  end
+
+  def test_java_env_apple
+    ENV.expects(:prepend_path)
+    ENV.expects(:append_to_cflags)
+    @java_req.modify_build_environment
+    assert_equal ENV["JAVA_HOME"], @tmp_java_home
+  end
+
+  def test_java_env_oracle
+    FileUtils.mkdir @tmp_pathname/"include"
+    ENV.expects(:prepend_path)
+    ENV.expects(:append_to_cflags).twice
+    @java_req.modify_build_environment
+    assert_equal ENV["JAVA_HOME"], @tmp_java_home
+  end
+end