Add Task#[]

spec/build_tests_spec.rb

@@ -2885,6 +2885,27 @@ EOF
     expect(result.stdout).to eq %[four\nmyparam:"cli-value"\nmyp2:"--myp2"\none\n]
   end
 
+  it "allows accessing task arguments via Task#[]" do
+    test_dir "tasks"
+    result = run_rscons(args: %w[-f tasks.rb configure])
+    result = run_rscons(args: %w[-f tasks.rb five])
+    expect(result.stderr).to eq ""
+    expect(result.status).to eq 0
+    expect(result.stdout).to match /four myparam value is defaultvalue/
+    result = run_rscons(args: %w[-f tasks.rb four --myparam=v42 five])
+    expect(result.stderr).to eq ""
+    expect(result.status).to eq 0
+    expect(result.stdout).to match /four myparam value is v42/
+  end
+
+  it "exits with an error when attempting to get a nonexistent parameter value" do
+    test_dir "tasks"
+    result = run_rscons(args: %w[-f tasks.rb configure])
+    result = run_rscons(args: %w[-f tasks.rb six])
+    expect(result.stderr).to match /Could not find parameter 'nope'/
+    expect(result.status).to_not eq 0
+  end
+
   it "displays tasks and their arguments in the help info" do
     test_dir "tasks"
     result = run_rscons(args: %w[-f tasks.rb -h])