Support user .bazeliskrc in addition to workspace root .bazeliskrc (

#390)

* core: Implement fallback to .bazeliskrc in the user home directory

* README.md: Documentation for ~/.bazeliskrc usage

* bazelisk_test.sh: Integration test for user home ~/.bazeliskrc precedence

* bazelisk_test.sh: Set USERPROFILE as user home for compatibility with Windows

README.md

@@ -129,7 +129,7 @@ You can control the user agent that Bazelisk sends in all HTTP requests by setti
 
 # .bazeliskrc configuration file
 
-The Go version supports a `.bazeliskrc` file in the root directory of a workspace. This file allows users to set environment variables persistently.
+The Go version supports a `.bazeliskrc` file in the root directory of a workspace and the user home directory. This file allows users to set environment variables persistently.
 
 Example file content:
 
@@ -151,7 +151,11 @@ The following variables can be set:
 - `BAZELISK_USER_AGENT`
 - `USE_BAZEL_VERSION`
 
-Please note that the actual environment variables take precedence over those in the `.bazeliskrc` file.
+Configuration variables are evaluated with precedence order. The preferred values are derived in order from highest to lowest precedence as follows:
+
+* Variables defined in the environment
+* Variables defined in the workspace root `.bazeliskrc`
+* Variables defined in the user home `.bazeliskrc`
 
 ## Requirements
 

bazelisk_test.sh

@@ -43,6 +43,8 @@ shift 1
 # GitHub by default, whereas the Go version GCS (without this json file)
 function setup() {
   unset USE_BAZEL_VERSION
+
+  USER_HOME="$(mktemp -d $TEST_TMPDIR/user.XXXXXX)"
   BAZELISK_HOME="$(mktemp -d $TEST_TMPDIR/home.XXXXXX)"
 
   cp "$(rlocation __main__/releases_for_tests.json)" "${BAZELISK_HOME}/bazelbuild-releases.json"
@@ -129,12 +131,41 @@ function test_bazel_version_prefer_environment_to_bazeliskrc() {
       (echo "FAIL: Expected to find 'Build label: 0.20.0' in the output of 'bazelisk version'"; exit 1)
 }
 
-function test_bazel_version_from_bazeliskrc() {
+function test_bazel_version_from_workspace_bazeliskrc() {
+  setup
+
+  echo "USE_BAZEL_VERSION=0.19.0" > .bazeliskrc
+
+  BAZELISK_HOME="$BAZELISK_HOME" \
+      bazelisk version 2>&1 | tee log
+
+  grep "Build label: 0.19.0" log || \
+      (echo "FAIL: Expected to find 'Build label: 0.19.0' in the output of 'bazelisk version'"; exit 1)
+}
+
+function test_bazel_version_from_user_home_bazeliskrc() {
+  setup
+
+  echo "USE_BAZEL_VERSION=0.19.0" > "${USER_HOME}/.bazeliskrc"
+
+  BAZELISK_HOME="$BAZELISK_HOME" \
+      HOME="$USER_HOME" \
+      USERPROFILE="$USER_HOME" \
+      bazelisk version 2>&1 | tee log
+
+  grep "Build label: 0.19.0" log || \
+      (echo "FAIL: Expected to find 'Build label: 0.19.0' in the output of 'bazelisk version'"; exit 1)
+}
+
+function test_bazel_version_prefer_workspace_bazeliskrc_to_user_home_bazeliskrc() {
   setup
 
   echo "USE_BAZEL_VERSION=0.19.0" > .bazeliskrc
+  echo "USE_BAZEL_VERSION=0.20.0" > "${USER_HOME}/.bazeliskrc"
 
   BAZELISK_HOME="$BAZELISK_HOME" \
+      HOME="$USER_HOME" \
+      USERPROFILE="$USER_HOME" \
       bazelisk version 2>&1 | tee log
 
   grep "Build label: 0.19.0" log || \
@@ -360,8 +391,16 @@ if [[ $BAZELISK_VERSION == "GO" ]]; then
   test_bazel_version_prefer_environment_to_bazeliskrc
   echo
 
-  echo "# test_bazel_version_from_bazeliskrc"
-  test_bazel_version_from_bazeliskrc
+  echo "# test_bazel_version_from_workspace_bazeliskrc"
+  test_bazel_version_from_workspace_bazeliskrc
+  echo
+
+  echo "# test_bazel_version_from_user_home_bazeliskrc"
+  test_bazel_version_from_user_home_bazeliskrc
+  echo
+
+  echo "# test_bazel_version_prefer_workspace_bazeliskrc_to_user_home_bazeliskrc"
+  test_bazel_version_prefer_workspace_bazeliskrc_to_user_home_bazeliskrc
   echo
 
   echo "# test_bazel_version_prefer_bazeliskrc_to_bazelversion_file"

core/core.go

@@ -29,6 +29,7 @@ const (
 	bazelReal      = "BAZEL_REAL"
 	skipWrapperEnv = "BAZELISK_SKIP_WRAPPER"
 	wrapperPath    = "./tools/bazel"
+	rcFileName     = ".bazeliskrc"
 )
 
 var (
@@ -196,40 +197,85 @@ func GetEnvOrConfig(name string) string {
 		return val
 	}
 
-	// Parse .bazeliskrc in the workspace root, once, if it can be found.
-	fileConfigOnce.Do(func() {
-		workingDirectory, err := os.Getwd()
+	fileConfigOnce.Do(loadFileConfig)
+
+	return fileConfig[name]
+}
+
+// loadFileConfig locates available .bazeliskrc configuration files, parses them with a precedence order preference,
+// and updates a global configuration map with their contents. This routine should be executed exactly once.
+func loadFileConfig() {
+	var rcFilePaths []string
+
+	if userRC, err := locateUserConfigFile(); err == nil {
+		rcFilePaths = append(rcFilePaths, userRC)
+	}
+	if workspaceRC, err := locateWorkspaceConfigFile(); err == nil {
+		rcFilePaths = append(rcFilePaths, workspaceRC)
+	}
+
+	fileConfig = make(map[string]string)
+	for _, rcPath := range rcFilePaths {
+		config, err := parseFileConfig(rcPath)
 		if err != nil {
-			return
+			log.Fatal(err)
 		}
-		workspaceRoot := findWorkspaceRoot(workingDirectory)
-		if workspaceRoot == "" {
-			return
+
+		for key, value := range config {
+			fileConfig[key] = value
 		}
-		rcFilePath := filepath.Join(workspaceRoot, ".bazeliskrc")
-		contents, err := ioutil.ReadFile(rcFilePath)
-		if err != nil {
-			if os.IsNotExist(err) {
-				return
-			}
-			log.Fatal(err)
+	}
+}
+
+// locateWorkspaceConfigFile locates a .bazeliskrc file in the current workspace root.
+func locateWorkspaceConfigFile() (string, error) {
+	workingDirectory, err := os.Getwd()
+	if err != nil {
+		return "", err
+	}
+	workspaceRoot := findWorkspaceRoot(workingDirectory)
+	if workspaceRoot == "" {
+		return "", err
+	}
+	return filepath.Join(workspaceRoot, rcFileName), nil
+}
+
+// locateUserConfigFile locates a .bazeliskrc file in the user's home directory.
+func locateUserConfigFile() (string, error) {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(home, rcFileName), nil
+}
+
+// parseFileConfig parses a .bazeliskrc file as a map of key-value configuration values.
+func parseFileConfig(rcFilePath string) (map[string]string, error) {
+	config := make(map[string]string)
+
+	contents, err := ioutil.ReadFile(rcFilePath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			// Non-critical error.
+			return config, nil
 		}
-		fileConfig = make(map[string]string)
-		for _, line := range strings.Split(string(contents), "\n") {
-			if strings.HasPrefix(line, "#") {
-				// comments
-				continue
-			}
-			parts := strings.SplitN(line, "=", 2)
-			if len(parts) < 2 {
-				continue
-			}
-			key := strings.TrimSpace(parts[0])
-			fileConfig[key] = strings.TrimSpace(parts[1])
+		return nil, err
+	}
+
+	for _, line := range strings.Split(string(contents), "\n") {
+		if strings.HasPrefix(line, "#") {
+			// comments
+			continue
 		}
-	})
+		parts := strings.SplitN(line, "=", 2)
+		if len(parts) < 2 {
+			continue
+		}
+		key := strings.TrimSpace(parts[0])
+		config[key] = strings.TrimSpace(parts[1])
+	}
 
-	return fileConfig[name]
+	return config, nil
 }
 
 // isValidWorkspace returns true iff the supplied path is the workspace root, defined by the presence of