command/cliconfig: Factor out CLI config handling

This is just a wholesale move of the CLI configuration types and functions
from the main package into its own package, leaving behind some type
aliases and wrappers for now to keep existing callers working.

This commit alone doesn't really achieve anything, but in future commits
we'll expand the functionality in this package.

Author: apparentlymart

command/cliconfig/cliconfig.go

@@ -0,0 +1,354 @@
+// Package cliconfig has the types representing and the logic to load CLI-level
+// configuration settings.
+//
+// The CLI config is a small collection of settings that a user can override via
+// some files in their home directory or, in some cases, via environment
+// variables. The CLI config is not the same thing as a Terraform configuration
+// written in the Terraform language; the logic for those lives in the top-level
+// directory "configs".
+package cliconfig
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+
+	"github.com/hashicorp/hcl"
+
+	"github.com/hashicorp/terraform/command"
+	"github.com/hashicorp/terraform/svchost"
+	"github.com/hashicorp/terraform/tfdiags"
+)
+
+const pluginCacheDirEnvVar = "TF_PLUGIN_CACHE_DIR"
+
+// Config is the structure of the configuration for the Terraform CLI.
+//
+// This is not the configuration for Terraform itself. That is in the
+// "config" package.
+type Config struct {
+	Providers    map[string]string
+	Provisioners map[string]string
+
+	DisableCheckpoint          bool `hcl:"disable_checkpoint"`
+	DisableCheckpointSignature bool `hcl:"disable_checkpoint_signature"`
+
+	// If set, enables local caching of plugins in this directory to
+	// avoid repeatedly re-downloading over the Internet.
+	PluginCacheDir string `hcl:"plugin_cache_dir"`
+
+	Hosts map[string]*ConfigHost `hcl:"host"`
+
+	Credentials        map[string]map[string]interface{}   `hcl:"credentials"`
+	CredentialsHelpers map[string]*ConfigCredentialsHelper `hcl:"credentials_helper"`
+}
+
+// ConfigHost is the structure of the "host" nested block within the CLI
+// configuration, which can be used to override the default service host
+// discovery behavior for a particular hostname.
+type ConfigHost struct {
+	Services map[string]interface{} `hcl:"services"`
+}
+
+// ConfigCredentialsHelper is the structure of the "credentials_helper"
+// nested block within the CLI configuration.
+type ConfigCredentialsHelper struct {
+	Args []string `hcl:"args"`
+}
+
+// BuiltinConfig is the built-in defaults for the configuration. These
+// can be overridden by user configurations.
+var BuiltinConfig Config
+
+// PluginOverrides are paths that override discovered plugins, set from
+// the config file.
+var PluginOverrides command.PluginOverrides
+
+// ConfigFile returns the default path to the configuration file.
+//
+// On Unix-like systems this is the ".terraformrc" file in the home directory.
+// On Windows, this is the "terraform.rc" file in the application data
+// directory.
+func ConfigFile() (string, error) {
+	return configFile()
+}
+
+// ConfigDir returns the configuration directory for Terraform.
+func ConfigDir() (string, error) {
+	return configDir()
+}
+
+// LoadConfig reads the CLI configuration from the various filesystem locations
+// and from the environment, returning a merged configuration along with any
+// diagnostics (errors and warnings) encountered along the way.
+func LoadConfig() (*Config, tfdiags.Diagnostics) {
+	var diags tfdiags.Diagnostics
+	configVal := BuiltinConfig // copy
+	config := &configVal
+
+	if mainFilename, err := cliConfigFile(); err == nil {
+		if _, err := os.Stat(mainFilename); err == nil {
+			mainConfig, mainDiags := loadConfigFile(mainFilename)
+			diags = diags.Append(mainDiags)
+			config = config.Merge(mainConfig)
+		}
+	}
+
+	if configDir, err := ConfigDir(); err == nil {
+		if info, err := os.Stat(configDir); err == nil && info.IsDir() {
+			dirConfig, dirDiags := loadConfigDir(configDir)
+			diags = diags.Append(dirDiags)
+			config = config.Merge(dirConfig)
+		}
+	}
+
+	if envConfig := EnvConfig(); envConfig != nil {
+		// envConfig takes precedence
+		config = envConfig.Merge(config)
+	}
+
+	diags = diags.Append(config.Validate())
+
+	return config, diags
+}
+
+// loadConfigFile loads the CLI configuration from ".terraformrc" files.
+func loadConfigFile(path string) (*Config, tfdiags.Diagnostics) {
+	var diags tfdiags.Diagnostics
+	result := &Config{}
+
+	log.Printf("Loading CLI configuration from %s", path)
+
+	// Read the HCL file and prepare for parsing
+	d, err := ioutil.ReadFile(path)
+	if err != nil {
+		diags = diags.Append(fmt.Errorf("Error reading %s: %s", path, err))
+		return result, diags
+	}
+
+	// Parse it
+	obj, err := hcl.Parse(string(d))
+	if err != nil {
+		diags = diags.Append(fmt.Errorf("Error parsing %s: %s", path, err))
+		return result, diags
+	}
+
+	// Build up the result
+	if err := hcl.DecodeObject(&result, obj); err != nil {
+		diags = diags.Append(fmt.Errorf("Error parsing %s: %s", path, err))
+		return result, diags
+	}
+
+	// Replace all env vars
+	for k, v := range result.Providers {
+		result.Providers[k] = os.ExpandEnv(v)
+	}
+	for k, v := range result.Provisioners {
+		result.Provisioners[k] = os.ExpandEnv(v)
+	}
+
+	if result.PluginCacheDir != "" {
+		result.PluginCacheDir = os.ExpandEnv(result.PluginCacheDir)
+	}
+
+	return result, diags
+}
+
+func loadConfigDir(path string) (*Config, tfdiags.Diagnostics) {
+	var diags tfdiags.Diagnostics
+	result := &Config{}
+
+	entries, err := ioutil.ReadDir(path)
+	if err != nil {
+		diags = diags.Append(fmt.Errorf("Error reading %s: %s", path, err))
+		return result, diags
+	}
+
+	for _, entry := range entries {
+		name := entry.Name()
+		// Ignoring errors here because it is used only to indicate pattern
+		// syntax errors, and our patterns are hard-coded here.
+		hclMatched, _ := filepath.Match("*.tfrc", name)
+		jsonMatched, _ := filepath.Match("*.tfrc.json", name)
+		if !(hclMatched || jsonMatched) {
+			continue
+		}
+
+		filePath := filepath.Join(path, name)
+		fileConfig, fileDiags := loadConfigFile(filePath)
+		diags = diags.Append(fileDiags)
+		result = result.Merge(fileConfig)
+	}
+
+	return result, diags
+}
+
+// EnvConfig returns a Config populated from environment variables.
+//
+// Any values specified in this config should override those set in the
+// configuration file.
+func EnvConfig() *Config {
+	config := &Config{}
+
+	if envPluginCacheDir := os.Getenv(pluginCacheDirEnvVar); envPluginCacheDir != "" {
+		// No Expandenv here, because expanding environment variables inside
+		// an environment variable would be strange and seems unnecessary.
+		// (User can expand variables into the value while setting it using
+		// standard shell features.)
+		config.PluginCacheDir = envPluginCacheDir
+	}
+
+	return config
+}
+
+// Validate checks for errors in the configuration that cannot be detected
+// just by HCL decoding, returning any problems as diagnostics.
+//
+// On success, the returned diagnostics will return false from the HasErrors
+// method. A non-nil diagnostics is not necessarily an error, since it may
+// contain just warnings.
+func (c *Config) Validate() tfdiags.Diagnostics {
+	var diags tfdiags.Diagnostics
+
+	if c == nil {
+		return diags
+	}
+
+	// FIXME: Right now our config parsing doesn't retain enough information
+	// to give proper source references to any errors. We should improve
+	// on this when we change the CLI config parser to use HCL2.
+
+	// Check that all "host" blocks have valid hostnames.
+	for givenHost := range c.Hosts {
+		_, err := svchost.ForComparison(givenHost)
+		if err != nil {
+			diags = diags.Append(
+				fmt.Errorf("The host %q block has an invalid hostname: %s", givenHost, err),
+			)
+		}
+	}
+
+	// Check that all "credentials" blocks have valid hostnames.
+	for givenHost := range c.Credentials {
+		_, err := svchost.ForComparison(givenHost)
+		if err != nil {
+			diags = diags.Append(
+				fmt.Errorf("The credentials %q block has an invalid hostname: %s", givenHost, err),
+			)
+		}
+	}
+
+	// Should have zero or one "credentials_helper" blocks
+	if len(c.CredentialsHelpers) > 1 {
+		diags = diags.Append(
+			fmt.Errorf("No more than one credentials_helper block may be specified"),
+		)
+	}
+
+	return diags
+}
+
+// Merge merges two configurations and returns a third entirely
+// new configuration with the two merged.
+func (c1 *Config) Merge(c2 *Config) *Config {
+	var result Config
+	result.Providers = make(map[string]string)
+	result.Provisioners = make(map[string]string)
+	for k, v := range c1.Providers {
+		result.Providers[k] = v
+	}
+	for k, v := range c2.Providers {
+		if v1, ok := c1.Providers[k]; ok {
+			log.Printf("[INFO] Local %s provider configuration '%s' overrides '%s'", k, v, v1)
+		}
+		result.Providers[k] = v
+	}
+	for k, v := range c1.Provisioners {
+		result.Provisioners[k] = v
+	}
+	for k, v := range c2.Provisioners {
+		if v1, ok := c1.Provisioners[k]; ok {
+			log.Printf("[INFO] Local %s provisioner configuration '%s' overrides '%s'", k, v, v1)
+		}
+		result.Provisioners[k] = v
+	}
+	result.DisableCheckpoint = c1.DisableCheckpoint || c2.DisableCheckpoint
+	result.DisableCheckpointSignature = c1.DisableCheckpointSignature || c2.DisableCheckpointSignature
+
+	result.PluginCacheDir = c1.PluginCacheDir
+	if result.PluginCacheDir == "" {
+		result.PluginCacheDir = c2.PluginCacheDir
+	}
+
+	if (len(c1.Hosts) + len(c2.Hosts)) > 0 {
+		result.Hosts = make(map[string]*ConfigHost)
+		for name, host := range c1.Hosts {
+			result.Hosts[name] = host
+		}
+		for name, host := range c2.Hosts {
+			result.Hosts[name] = host
+		}
+	}
+
+	if (len(c1.Credentials) + len(c2.Credentials)) > 0 {
+		result.Credentials = make(map[string]map[string]interface{})
+		for host, creds := range c1.Credentials {
+			result.Credentials[host] = creds
+		}
+		for host, creds := range c2.Credentials {
+			// We just clobber an entry from the other file right now. Will
+			// improve on this later using the more-robust merging behavior
+			// built in to HCL2.
+			result.Credentials[host] = creds
+		}
+	}
+
+	if (len(c1.CredentialsHelpers) + len(c2.CredentialsHelpers)) > 0 {
+		result.CredentialsHelpers = make(map[string]*ConfigCredentialsHelper)
+		for name, helper := range c1.CredentialsHelpers {
+			result.CredentialsHelpers[name] = helper
+		}
+		for name, helper := range c2.CredentialsHelpers {
+			result.CredentialsHelpers[name] = helper
+		}
+	}
+
+	return &result
+}
+
+func cliConfigFile() (string, error) {
+	mustExist := true
+
+	configFilePath := os.Getenv("TF_CLI_CONFIG_FILE")
+	if configFilePath == "" {
+		configFilePath = os.Getenv("TERRAFORM_CONFIG")
+	}
+
+	if configFilePath == "" {
+		var err error
+		configFilePath, err = ConfigFile()
+		mustExist = false
+
+		if err != nil {
+			log.Printf(
+				"[ERROR] Error detecting default CLI config file path: %s",
+				err)
+		}
+	}
+
+	log.Printf("[DEBUG] Attempting to open CLI config file: %s", configFilePath)
+	f, err := os.Open(configFilePath)
+	if err == nil {
+		f.Close()
+		return configFilePath, nil
+	}
+
+	if mustExist || !os.IsNotExist(err) {
+		return "", err
+	}
+
+	log.Println("[DEBUG] File doesn't exist, but doesn't need to. Ignoring.")
+	return "", nil
+}

config_test.go renamed to command/cliconfig/cliconfig_test.go

@@ -1,4 +1,4 @@
-package main
+package cliconfig
 
 import (
 	"os"

config_unix.go renamed to command/cliconfig/config_unix.go

@@ -1,6 +1,6 @@
 // +build !windows
 
-package main
+package cliconfig
 
 import (
 	"errors"

config_windows.go renamed to command/cliconfig/config_windows.go

@@ -1,6 +1,6 @@
 // +build windows
 
-package main
+package cliconfig
 
 import (
 	"path/filepath"

testdata/config renamed to command/cliconfig/testdata/config

@@ -25,6 +25,11 @@ var PlumbingCommands map[string]struct{}
 // Ui is the cli.Ui used for communicating to the outside world.
 var Ui cli.Ui
 
+// PluginOverrides is set from wrappedMain during configuration processing
+// and then eventually passed to the "command" package to specify alternative
+// plugin locations via the legacy configuration file mechanism.
+var PluginOverrides command.PluginOverrides
+
 const (
 	ErrorPrefix  = "e:"
 	OutputPrefix = "o:"