Add configuration handling from environment variables (#84)

Adds environment variable handling for common configuration variables.

Based on #83.

include/Config/CLIConfig.h

@@ -32,6 +32,7 @@ llvm::cl::OptionCategory &getQSSCCategory();
 ///
 /// The qss-compiler adds several cli arguments to
 /// configure the QSSConfig through the CLIConfigBuilder.
+///
 /// These currently are:
 /// - `--target=<str>`: Sets QSSConfig::targetName.
 /// - `--config=<str>`: Sets QSSConfig::targetConfigPath.

include/Config/EnvVarConfig.h

@@ -0,0 +1,43 @@
+//===- EnvVarConfig.h - EnvVar Configuration builder ----------*- C++-*----===//
+//
+// (C) Copyright IBM 2023.
+//
+// Any modifications or derivative works of this code must retain this
+// copyright notice, and modified files need to carry a notice indicating
+// that they have been altered from the originals.
+//
+//===----------------------------------------------------------------------===//
+///
+/// Populate the configuration from environment variables.
+///
+//===----------------------------------------------------------------------===//
+#ifndef QSSC_ENVVARCONFIG_H
+#define QSSC_ENVVARCONFIG_H
+
+#include "Config/QSSConfig.h"
+
+namespace qssc::config {
+
+/// @brief Populate arguments of the QSSConfig
+/// from environment variables.
+///
+///
+/// The qss-compiler makes several several QSSConfig configuration
+/// options configurable from environment variables through the
+/// EnvVarConfigBuilder.
+///
+/// These currently are:
+/// - `QSSC_TARGET_NAME`: Sets QSSConfig::targetName.
+/// - `QSSC_TARGET_CONFIG_PATH`: Sets QSSConfig::targetConfigPath.
+///
+class EnvVarConfigBuilder : public QSSConfigBuilder {
+public:
+ llvm::Error populateConfig(QSSConfig &config) override;
+
+private:
+ llvm::Error populateConfigurationPath_(QSSConfig &config);
+ llvm::Error populateTarget_(QSSConfig &config);
+};
+
+} // namespace qssc::config
+#endif // QSS_ENVVARCONFIG_H

lib/API/api.cpp

@@ -16,6 +16,7 @@
 
 #include "API/api.h"
 #include "Config/CLIConfig.h"
+#include "Config/EnvVarConfig.h"
 
 #include "mlir/IR/AsmState.h"
 #include "mlir/IR/BuiltinOps.h"
@@ -301,16 +302,31 @@ static void printVersion(llvm::raw_ostream &out) {
 
 /// @brief Build the QSSConfig using the standard sources and assign to the
 /// supplied context.
+///
+/// The configuration precedence order is
+/// 1. Default values
+/// 2. Environment variables
+/// 3. CLI arguments.
+///
 /// @param context The context to build and register the configuration for.
+/// @return The constructed configuration that has been registered for the
+/// supplied context.
 static llvm::Expected<const qssc::config::QSSConfig &>
 buildConfig_(mlir::MLIRContext *context) {
- // Build configuration only from the CLI for now.
- auto config = qssc::config::CLIConfigBuilder().buildConfig();
+ // First populate the configuration from default values then
+ // environment variables.
+ auto config = qssc::config::EnvVarConfigBuilder().buildConfig();
  if (auto err = config.takeError())
  // Explicit move required for some systems as automatic move
  // is not recognized.
  return std::move(err);
 
+ // Apply CLI options of top of the configuration constructed above.
+ if (auto err = qssc::config::CLIConfigBuilder().populateConfig(*config))
+ // Explicit move required for some systems as automatic move
+ // is not recognized.
+ return std::move(err);
+
  // Set this as the configuration for the current context
  qssc::config::setContextConfig(context, std::move(*config));
 

lib/Config/CMakeLists.txt

@@ -8,6 +8,7 @@
 qssc_add_library(QSSConfig
  QSSConfig.cpp
  CLIConfig.cpp
+ EnvVarConfig.cpp
 
  ADDITIONAL_HEADER_DIRS
  ${QSSC_INCLUDE_DIR}/Config

lib/Config/EnvVarConfig.cpp

@@ -0,0 +1,41 @@
+//===- EnvVarConfigBuilder.cpp - QSSConfig from EnvVars ----* C++*--------===//
+//
+// (C) Copyright IBM 2023.
+//
+// Any modifications or derivative works of this code must retain this
+// copyright notice, and modified files need to carry a notice indicating
+// that they have been altered from the originals.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements building the configuration from environemnt variables.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Config/EnvVarConfig.h"
+
+#include <cstdlib>
+
+using namespace qssc::config;
+
+llvm::Error EnvVarConfigBuilder::populateConfig(QSSConfig &config) {
+ if (auto err = populateConfigurationPath_(config))
+ return err;
+
+ if (auto err = populateTarget_(config))
+ return err;
+
+ return llvm::Error::success();
+}
+
+llvm::Error EnvVarConfigBuilder::populateConfigurationPath_(QSSConfig &config) {
+ if (const char *configurationPath = std::getenv("QSSC_TARGET_CONFIG_PATH"))
+ config.targetConfigPath = configurationPath;
+ return llvm::Error::success();
+}
+
+llvm::Error EnvVarConfigBuilder::populateTarget_(QSSConfig &config) {
+ if (const char *targetStr = std::getenv("QSSC_TARGET_NAME"))
+ config.targetName = targetStr;
+ return llvm::Error::success();
+}

test/Config/test-config.tst

@@ -1,6 +1,12 @@
 // RUN: qss-compiler --target Mock --config path/to/config --allow-unregistered-dialect=false --add-target-passes=false --show-config | FileCheck %s --check-prefix CLI
+// RUN: QSSC_TARGET_NAME="MockEnv" QSSC_TARGET_CONFIG_PATH="path/to/config/Env" qss-compiler --allow-unregistered-dialect=false --add-target-passes=false --show-config | FileCheck %s --check-prefix ENV
 
 // CLI: targetName: Mock
 // CLI: targetConfigPath: path/to/config
 // CLI: allowUnregisteredDialects: 0
 // CLI: addTargetPasses: 0
+
+// ENV: targetName: MockEnv
+// ENV: targetConfigPath: path/to/config/Env
+// ENV: allowUnregisteredDialects: 0
+// ENV: addTargetPasses: 0