parse the endpoint into a URL up front, and gather the proxy from the env up front so that typos and malformed urls will surface immediately

Author: peterguy

cmd/src/main.go

@@ -3,9 +3,11 @@ package main
 import (
 	"encoding/json"
 	"flag"
+	"fmt"
 	"io"
 	"log"
 	"net"
+	"net/http"
 	"net/url"
 	"os"
 	"path/filepath"
@@ -158,7 +160,8 @@ func (c *config) apiClient(flags *api.Flags, out io.Writer) api.Client {
 	})
 }
 
-// readConfig reads the config file from the given path.
+// readConfig reads the config from the standard config file, the (deprecated) user-specified config file,
+// the environment variables, and the (deprecated) command-line flags.
 func readConfig() (*config, error) {
 	cfgFile := *configPath
 	userSpecified := *configPath != ""
@@ -271,12 +274,20 @@ func readConfig() (*config, error) {
 				return nil, errors.Newf("invalid proxy configuration: %w", err)
 			}
 			if !isValidUDS {
-				return nil, errors.Newf("invalid proxy socket: %s", path)
+				return nil, errors.Newf("Invalid proxy socket: %s", path)
 			}
 			cfg.proxyPath = path
 		} else {
 			return nil, errors.Newf("invalid proxy endpoint: %s", proxyStr)
 		}
+	} else {
+		// no SRC_PROXY; check for the standard proxy env variables HTTP_PROXY, HTTPS_PROXY, and NO_PROXY
+		if u, err := http.ProxyFromEnvironment(&http.Request{URL: cfg.endpointURL}); err != nil {
+			// when there's an error, the value for the env variable is not a legit URL
+			return nil, fmt.Errorf("Invalid HTTP_PROXY or HTTPS_PROXY value: %w", err)
+		} else {
+			cfg.proxyURL = u
+		}
 	}
 
 	cfg.additionalHeaders = parseAdditionalHeaders()