coder
diff --git a/‎buildinfo/buildinfo.go
Lines changed: 21 additions & 1 deletion b/‎buildinfo/buildinfo.go
Lines changed: 21 additions & 1 deletion
diff --git a/‎buildinfo/buildinfo_test.go
Lines changed: 67 additions & 0 deletions b/‎buildinfo/buildinfo_test.go
Lines changed: 67 additions & 0 deletions
diff --git a/‎cli/login.go
Lines changed: 9 additions & 0 deletions b/‎cli/login.go
Lines changed: 9 additions & 0 deletions
diff --git a/‎cli/root.go
Lines changed: 64 additions & 3 deletions b/‎cli/root.go
Lines changed: 64 additions & 3 deletions
diff --git a/‎codersdk/buildinfo.go
Lines changed: 12 additions & 0 deletions b/‎codersdk/buildinfo.go
Lines changed: 12 additions & 0 deletions
diff --git a/‎site/src/api/typesGenerated.ts
Lines changed: 1 addition & 1 deletion b/‎site/src/api/typesGenerated.ts
Lines changed: 1 addition & 1 deletion
@@ -3,6 +3,7 @@ package buildinfo
 import (
 	"fmt"
 	"runtime/debug"
+	"strings"
 	"sync"
 	"time"
 
@@ -24,6 +25,11 @@ var (
 	tag string
 )
 
+const (
+	// develPrefix is prefixed to developer versions of the application.
+	develPrefix = "v0.0.0-devel"
+)
+
 // Version returns the semantic version of the build.
 // Use golang.org/x/mod/semver to compare versions.
 func Version() string {
@@ -35,7 +41,7 @@ func Version() string {
 		if tag == "" {
 			// This occurs when the tag hasn't been injected,
 			// like when using "go run".
-			version = "v0.0.0-devel" + revision
+			version = develPrefix + revision
 			return
 		}
 		version = "v" + tag
@@ -48,6 +54,20 @@ func Version() string {
 	return version
 }
 
+// VersionsMatch compares the two versions. It assumes the versions match if
+// the major and the minor versions are equivalent. Patch versions are
+// disregarded. If it detects that either version is a developer build it
+// returns true.
+func VersionsMatch(v1, v2 string) bool {
+	// Developer versions are disregarded...hopefully they know what they are
+	// doing.
+	if strings.HasPrefix(v1, develPrefix) || strings.HasPrefix(v2, develPrefix) {
+		return true
+	}
+
+	return semver.MajorMinor(v1) == semver.MajorMinor(v2)
+}
+
 // ExternalURL returns a URL referencing the current Coder version.
 // For production builds, this will link directly to a release.
 // For development builds, this will link to a commit.
 
@@ -1,6 +1,7 @@
 package buildinfo_test
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -29,4 +30,70 @@ func TestBuildInfo(t *testing.T) {
 		_, valid := buildinfo.Time()
 		require.False(t, valid)
 	})
+
+	t.Run("VersionsMatch", func(t *testing.T) {
+		t.Parallel()
+
+		type testcase struct {
+			name        string
+			v1          string
+			v2          string
+			expectMatch bool
+		}
+
+		cases := []testcase{
+			{
+				name:        "OK",
+				v1:          "v1.2.3",
+				v2:          "v1.2.3",
+				expectMatch: true,
+			},
+			// Test that we return true if a developer version is detected.
+			// Developers do not need to be warned of mismatched versions.
+			{
+				name:        "DevelIgnored",
+				v1:          "v0.0.0-devel+123abac",
+				v2:          "v1.2.3",
+				expectMatch: true,
+			},
+			// Our CI instance uses a "-devel" prerelease
+			// flag. This is not the same as a developer WIP build.
+			{
+				name:        "DevelPreleaseNotIgnored",
+				v1:          "v1.1.1-devel+123abac",
+				v2:          "v1.2.3",
+				expectMatch: false,
+			},
+			{
+				name:        "MajorMismatch",
+				v1:          "v1.2.3",
+				v2:          "v0.1.2",
+				expectMatch: false,
+			},
+			{
+				name:        "MinorMismatch",
+				v1:          "v1.2.3",
+				v2:          "v1.3.2",
+				expectMatch: false,
+			},
+			// Different patches are ok, breaking changes are not allowed
+			// in patches.
+			{
+				name:        "PatchMismatch",
+				v1:          "v1.2.3+hash.whocares",
+				v2:          "v1.2.4+somestuff.hm.ok",
+				expectMatch: true,
+			},
+		}
+
+		for _, c := range cases {
+			c := c
+			t.Run(c.name, func(t *testing.T) {
+				t.Parallel()
+				require.Equal(t, c.expectMatch, buildinfo.VersionsMatch(c.v1, c.v2),
+					fmt.Sprintf("expected match=%v for version %s and %s", c.expectMatch, c.v1, c.v2),
+				)
+			})
+		}
+	})
 }
@@ -67,6 +67,15 @@ func login() *cobra.Command {
 			}
 
 			client := codersdk.New(serverURL)
+
+			// Try to check the version of the server prior to logging in.
+			// It may be useful to warn the user if they are trying to login
+			// on a very old client.
+			err = checkVersions(cmd, client)
+			if err != nil {
+				return xerrors.Errorf("check versions: %w", err)
+			}
+
 			hasInitialUser, err := client.HasFirstUser(cmd.Context())
 			if err != nil {
 				return xerrors.Errorf("has initial user: %w", err)
 
@@ -4,11 +4,13 @@ import (
 	"fmt"
 	"net/url"
 	"os"
+	"strconv"
 	"strings"
 	"time"
 
 	"golang.org/x/xerrors"
 
+	"github.com/charmbracelet/lipgloss"
 	"github.com/kirsle/configdir"
 	"github.com/mattn/go-isatty"
 	"github.com/spf13/cobra"
@@ -40,7 +42,13 @@ const (
 	varForceTty        = "force-tty"
 	notLoggedInMessage = "You are not logged in. Try logging in using 'coder login <url>'."
 
-	envSessionToken = "CODER_SESSION_TOKEN"
+	noVersionCheckFlag = "no-version-warning"
+	envNoVersionCheck  = "CODER_NO_VERSION_WARNING"
+)
+
+var (
+	errUnauthenticated = xerrors.New(notLoggedInMessage)
+	envSessionToken    = "CODER_SESSION_TOKEN"
 )
 
 func init() {
@@ -53,12 +61,37 @@ func init() {
 }
 
 func Root() *cobra.Command {
+	var varSuppressVersion bool
+
 	cmd := &cobra.Command{
 		Use:           "coder",
 		SilenceErrors: true,
 		SilenceUsage:  true,
 		Long: `Coder — A tool for provisioning self-hosted development environments.
 `,
+		PersistentPreRunE: func(cmd *cobra.Command, args []string) error {
+			if varSuppressVersion {
+				return nil
+			}
+
 			// Login handles checking the versions itself since it
+			// has a handle to an unauthenticated client.
+			if cmd.Name() == "login" {
+				return nil
+			}
+
+			client, err := createClient(cmd)
+			// If the client is unauthenticated we can ignore the check.
+			// The child commands should handle an unauthenticated client.
+			if xerrors.Is(err, errUnauthenticated) {
+				return nil
+			}
+			if err != nil {
+				return xerrors.Errorf("create client: %w", err)
+			}
+			return checkVersions(cmd, client)
+		},
+
 		Example: `  Start a Coder server.
   ` + cliui.Styles.Code.Render("$ coder server") + `
 
@@ -97,6 +130,7 @@ func Root() *cobra.Command {
 	cmd.SetUsageTemplate(usageTemplate())
 
 	cmd.PersistentFlags().String(varURL, "", "Specify the URL to your deployment.")
+	cliflag.BoolVarP(cmd.PersistentFlags(), &varSuppressVersion, noVersionCheckFlag, "", envNoVersionCheck, false, "Suppress warning when client and server versions do not match.")
 	cliflag.String(cmd.PersistentFlags(), varToken, "", envSessionToken, "", fmt.Sprintf("Specify an authentication token. For security reasons setting %s is preferred.", envSessionToken))
 	cliflag.String(cmd.PersistentFlags(), varAgentToken, "", "CODER_AGENT_TOKEN", "", "Specify an agent authentication token.")
 	_ = cmd.PersistentFlags().MarkHidden(varAgentToken)
@@ -142,7 +176,7 @@ func createClient(cmd *cobra.Command) (*codersdk.Client, error) {
 		if err != nil {
 			// If the configuration files are absent, the user is logged out
 			if os.IsNotExist(err) {
-				return nil, xerrors.New(notLoggedInMessage)
+				return nil, errUnauthenticated
 			}
 			return nil, err
 		}
@@ -157,7 +191,7 @@ func createClient(cmd *cobra.Command) (*codersdk.Client, error) {
 		if err != nil {
 			// If the configuration files are absent, the user is logged out
 			if os.IsNotExist(err) {
-				return nil, xerrors.New(notLoggedInMessage)
+				return nil, errUnauthenticated
 			}
 			return nil, err
 		}
@@ -331,3 +365,30 @@ func FormatCobraError(err error, cmd *cobra.Command) string {
 	helpErrMsg := fmt.Sprintf("Run '%s --help' for usage.", cmd.CommandPath())
 	return cliui.Styles.Error.Render(err.Error() + "\n" + helpErrMsg)
 }
+
+func checkVersions(cmd *cobra.Command, client *codersdk.Client) error {
+	flag := cmd.Flag("no-version-warning")
+	if suppress, _ := strconv.ParseBool(flag.Value.String()); suppress {
+		return nil
+	}
+
+	clientVersion := buildinfo.Version()
+
+	info, err := client.BuildInfo(cmd.Context())
+	if err != nil {
+		return xerrors.Errorf("build info: %w", err)
+	}
+
+	fmtWarningText := `version mismatch: client %s, server %s
+download the server version with: 'curl -L https://coder.com/install.sh | sh -s -- --version %s'
+`
+
+	if !buildinfo.VersionsMatch(clientVersion, info.Version) {
+		warn := cliui.Styles.Warn.Copy().Align(lipgloss.Left)
+		// Trim the leading 'v', our install.sh script does not handle this case well.
+		_, _ = fmt.Fprintf(cmd.OutOrStdout(), warn.Render(fmtWarningText), clientVersion, info.Version, strings.TrimPrefix(info.CanonicalVersion(), "v"))
+		_, _ = fmt.Fprintln(cmd.OutOrStdout())
+	}
+
+	return nil
+}
@@ -4,6 +4,9 @@ import (
 	"context"
 	"encoding/json"
 	"net/http"
+	"strings"
+
+	"golang.org/x/mod/semver"
 )
 
 // BuildInfoResponse contains build information for this instance of Coder.
@@ -16,6 +19,15 @@ type BuildInfoResponse struct {
 	Version string `json:"version"`
 }
 
+// CanonicalVersion trims build information from the version.
+// E.g. 'v0.7.4-devel+11573034' -> 'v0.7.4'.
+func (b BuildInfoResponse) CanonicalVersion() string {
+	// We do a little hack here to massage the string into a form
+	// that works well with semver.
+	trimmed := strings.ReplaceAll(b.Version, "-devel+", "+devel-")
+	return semver.Canonical(trimmed)
+}
+
 // BuildInfo returns build information for this instance of Coder.
 func (c *Client) BuildInfo(ctx context.Context) (BuildInfoResponse, error) {
 	res, err := c.Request(ctx, http.MethodGet, "/api/v2/buildinfo", nil)
 
@@ -36,7 +36,7 @@ export interface AzureInstanceIdentityToken {
   readonly encoding: string
 }
 
-// From codersdk/buildinfo.go:10:6
+// From codersdk/buildinfo.go:13:6
 export interface BuildInfoResponse {
   readonly external_url: string
   readonly version: string