Create common build settings (#154)

Create common simple build settings for people to use so they don't recreate these rules over and over again. 

This fulfills part of the SBC design doc: https://docs.google.com/document/d/1vc8v-kXjvgZOdQdnxPTaV0rrLxtP2XwnD2tAZlYJOqw/edit#bookmark=id.iiumwic0jphr

rules/common_settings.bzl

@@ -0,0 +1,94 @@
+# Copyright 2019 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Common build setting rules
+
+These rules return a BuildSettingInfo with the value of the build setting.
+For label-typed settings, use the native label_flag and label_setting rules.
+
+More documentation on how to use build settings at
+https://docs.bazel.build/versions/master/skylark/config.html#user-defined-build-settings
+"""
+
+BuildSettingInfo = provider(
+    doc = "A singleton provider that contains the raw value of a build setting",
+    fields = ["value"]
+)
+
+def _impl(ctx):
+    return BuildSettingInfo(value = ctx.build_setting_value)
+
+int_flag = rule(
+    implementation = _impl,
+    build_setting = config.int(flag = True),
+    doc = "An int-typed build setting that can be set on the command line",
+)
+
+int_setting = rule(
+    implementation = _impl,
+    build_setting = config.int(),
+    doc = "An int-typed build setting that cannot be set on the command line",
+)
+
+bool_flag = rule(
+    implementation = _impl,
+    build_setting = config.bool(flag = True),
+    doc = "A bool-typed build setting that can be set on the command line",
+)
+
+bool_setting = rule(
+    implementation = _impl,
+    build_setting = config.bool(),
+    doc = "A bool-typed build setting that cannot be set on the command line",
+)
+
+string_list_flag = rule(
+    implementation = _impl,
+    build_setting = config.string_list(flag = True),
+    doc = "A string list-typed build setting that can be set on the command line",
+)
+
+string_list_setting = rule(
+    implementation = _impl,
+    build_setting = config.string_list(),
+    doc = "A string list-typed build setting that cannot be set on the command line",
+)
+
+def _string_impl(ctx):
+    allowed_values = ctx.attr.values
+    value = ctx.build_setting_value
+    if len(allowed_values) == 0 or value in ctx.attr.values:
+        return BuildSettingInfo(value = value)
+    else:
+      fail("Error setting "+ str(ctx.label) + ": invalid value '" + value + "'. Allowed values are " + str(allowed_values))
+
+string_flag = rule(
+    implementation = _string_impl,
+    build_setting = config.string(flag = True),
+    attrs = {
+        "values" : attr.string_list(
+            doc = "The list of allowed values for this setting. An error is raised if any other value is given."
+        )},
+    doc = "A string-typed build setting that can be set on the command line",
+)
+
+string_setting = rule(
+    implementation = _string_impl,
+    build_setting = config.string(),
+    attrs = {
+    "values" : attr.string_list(
+        doc = "The list of allowed values for this setting. An error is raised if any other value is given."
+    )},
+    doc = "A string-typed build setting that cannot be set on the command line",
+)

tests/BUILD

@@ -85,6 +85,17 @@ sh_test(
     tags = ["local"],
 )
 
+sh_test(
+    name = "common_settings_e2e_test",
+    srcs = ["common_settings_test.sh"],
+    data = [
+        ":unittest.bash",
+        "//rules:common_settings.bzl",
+        "@bazel_tools//tools/bash/runfiles",
+    ],
+    tags = ["local"],
+)
+
 shell_args_test_gen(
     name = "shell_spawn_e2e_test_src",
 )

tests/common_settings_test.sh

@@ -0,0 +1,169 @@
+#!/bin/bash
+
+# Copyright 2019 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# End to end tests for common_settings.bzl
+
+# --- begin runfiles.bash initialization ---
+set -euo pipefail
+if [[ ! -d "${RUNFILES_DIR:-/dev/null}" && ! -f "${RUNFILES_MANIFEST_FILE:-/dev/null}" ]]; then
+  if [[ -f "$0.runfiles_manifest" ]]; then
+    export RUNFILES_MANIFEST_FILE="$0.runfiles_manifest"
+  elif [[ -f "$0.runfiles/MANIFEST" ]]; then
+    export RUNFILES_MANIFEST_FILE="$0.runfiles/MANIFEST"
+  elif [[ -f "$0.runfiles/bazel_tools/tools/bash/runfiles/runfiles.bash" ]]; then
+    export RUNFILES_DIR="$0.runfiles"
+  fi
+fi
+if [[ -f "${RUNFILES_DIR:-/dev/null}/bazel_tools/tools/bash/runfiles/runfiles.bash" ]]; then
+  source "${RUNFILES_DIR}/bazel_tools/tools/bash/runfiles/runfiles.bash"
+elif [[ -f "${RUNFILES_MANIFEST_FILE:-/dev/null}" ]]; then
+  source "$(grep -m1 "^bazel_tools/tools/bash/runfiles/runfiles.bash " \
+            "$RUNFILES_MANIFEST_FILE" | cut -d ' ' -f 2-)"
+else
+  echo >&2 "ERROR: cannot find @bazel_tools//tools/bash/runfiles:runfiles.bash"
+  exit 1
+fi
+# --- end runfiles.bash initialization ---
+
+source "$(rlocation bazel_skylib/tests/unittest.bash)" \
+  || { echo "Could not source bazel_skylib/tests/unittest.bash" >&2; exit 1; }
+
+function create_volcano_pkg() {
+  local -r pkg="$1"
+  mkdir -p "$pkg"
+  cd "$pkg"
+
+  cat > WORKSPACE <<EOF
+workspace(name = 'bazel_skylib')
+EOF
+
+  mkdir -p rules
+  cat > rules/BUILD <<EOF
+exports_files(["*.bzl"])
+EOF
+
+  ln -sf "$(rlocation bazel_skylib/rules/common_settings.bzl)" rules/common_settings.bzl
+
+  mkdir -p volcano
+  cat > volcano/rules.bzl <<EOF
+load("//rules:common_settings.bzl", "BuildSettingInfo")
+
+def _volcano_impl(ctx):
+  description = struct(
+    height = ctx.attr.height[BuildSettingInfo].value,
+    active = ctx.attr.active[BuildSettingInfo].value,
+    namer = ctx.attr.namer[BuildSettingInfo].value,
+    nicknames = ctx.attr.nicknames[BuildSettingInfo].value
+  )
+  print(description)
+
+volcano = rule(
+  implementation = _volcano_impl,
+  attrs = {
+    "height" : attr.label(),
+    "active" : attr.label(),
+    "namer": attr.label(),
+    "nicknames": attr.label(),
+  }
+)
+EOF
+
+  cat > volcano/BUILD <<EOF
+load(
+  "//rules:common_settings.bzl",
+  "int_flag",
+  "int_setting",
+  "bool_flag",
+  "string_flag",
+  "string_list_flag",
+)
+load("//volcano:rules.bzl", "volcano")
+
+int_flag(
+  name = "height-flag",
+  build_setting_default = 9677 # pre-1980 explosion
+)
+
+bool_flag(
+  name = "active-flag",
+  build_setting_default = True
+)
+
+string_flag(
+  name = "namer-flag",
+  build_setting_default = "cpt-george-vancouver",
+  values = ["cpt-george-vancouver", "puyallup-tribe"]
+)
+
+string_list_flag(
+  name = "nicknames-flag",
+  build_setting_default = ["loowit", "loowitiatkla", "lavelatla"]
+)
+
+int_setting(
+  name = "height-setting",
+  build_setting_default = 9677
+)
+
+volcano(
+  name = "mt-st-helens",
+  height = ":height-flag",
+  active = ":active-flag",
+  namer = ":namer-flag",
+  nicknames = ":nicknames-flag",
+)
+EOF
+
+}
+
+function test_can_set_flags() {
+  local -r pkg="${FUNCNAME[0]}"
+  create_volcano_pkg "$pkg"
+
+  bazel build volcano:mt-st-helens --experimental_build_setting_api --//volcano:height-flag=8366 \
+    --//volcano:active-flag=False --//volcano:namer-flag=puyallup-tribe \
+    --//volcano:nicknames-flag=volcano-mc-volcanoface \
+    >"$TEST_log" 2>&1 || fail "Expected test to pass"
+
+  expect_log "active = False"
+  expect_log "height = 8366"
+  expect_log "namer = \"puyallup-tribe\""
+  expect_log "nicknames = \[\"volcano-mc-volcanoface\"\]"
+}
+
+function test_cannot_set_settings() {
+  local -r pkg="${FUNCNAME[0]}"
+  create_volcano_pkg "$pkg"
+
+  bazel build volcano:mt-st-helens --experimental_build_setting_api --//volcano:height-setting=8366 \
+    >"$TEST_log" 2>&1 && fail "Expected test to fail" || true
+
+  expect_log "Unrecognized option: //volcano:height-setting"
+}
+
+function test_not_allowed_value() {
+  local -r pkg="${FUNCNAME[0]}"
+  create_volcano_pkg "$pkg"
+
+  bazel build volcano:mt-st-helens --experimental_build_setting_api --//volcano:namer-flag=me \
+    >"$TEST_log" 2>&1 && fail "Expected test to fail" || true
+
+  expect_log "Error setting //volcano:namer-flag: invalid value 'me'. Allowed values are"
+}
+
+
+cd "$TEST_TMPDIR"
+run_suite "common_settings test suite"