coder · cmoog · Oct 27, 2020 · Oct 24, 2020 · Oct 24, 2020 · coadler
diff --git a/ci/steps/build.sh b/ci/steps/build.sh
@@ -13,7 +13,7 @@ build() {
 	echo "Building coder-cli for $GOOS-$GOARCH..."
 
 	tmpdir=$(mktemp -d)
-	go build -ldflags "-X main.version=${tag}" -o "$tmpdir/coder" ../../cmd/coder
+	go build -ldflags "-X cdr.dev/coder-cli/internal/version.Version=${tag}" -o "$tmpdir/coder" ../../cmd/coder
 
 	pushd "$tmpdir"
 	if [[ "$GOOS" == "windows" ]]; then

diff --git a/cmd/coder/main.go b/cmd/coder/main.go
@@ -11,12 +11,10 @@ import (
 
 	"cdr.dev/coder-cli/internal/clog"
 	"cdr.dev/coder-cli/internal/cmd"
+	"cdr.dev/coder-cli/internal/version"
 	"cdr.dev/coder-cli/internal/x/xterminal"
 )
 
-// Using a global for the version so it can be set at build time using ldflags.
-var version = "unknown"
-
 func main() {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
@@ -39,7 +37,7 @@ func main() {
 	}()
 
 	app := cmd.Make()
-	app.Version = fmt.Sprintf("%s %s %s/%s", version, runtime.Version(), runtime.GOOS, runtime.GOARCH)
+	app.Version = fmt.Sprintf("%s %s %s/%s", version.Version, runtime.Version(), runtime.GOOS, runtime.GOARCH)
 
 	if err := app.ExecuteContext(ctx); err != nil {
 		clog.Log(err)

diff --git a/coder-sdk/version.go b/coder-sdk/version.go
@@ -0,0 +1,22 @@
+package coder
+
+import (
+	"context"
+	"net/http"
+)
+
+// APIVersion parses the coder-version http header from an authenticated request.
+func (c Client) APIVersion(ctx context.Context) (string, error) {
+	const coderVersionHeaderKey = "coder-version"
+	resp, err := c.request(ctx, http.MethodGet, "/api/users/"+Me, nil)
+	if err != nil {
+		return "", err
+	}
+
+	version := resp.Header.Get(coderVersionHeaderKey)
+	if version == "" {
+		version = "unknown"
+	}
+
+	return version, nil
+}
diff --git a/internal/cmd/auth.go b/internal/cmd/auth.go
@@ -2,6 +2,7 @@ package cmd
 
 import (
 	"context"
+	"fmt"
 	"net/http"
 	"net/url"
 
@@ -10,6 +11,7 @@ import (
 	"cdr.dev/coder-cli/coder-sdk"
 	"cdr.dev/coder-cli/internal/clog"
 	"cdr.dev/coder-cli/internal/config"
+	"cdr.dev/coder-cli/internal/version"
 )
 
 var errNeedLogin = clog.Fatal(
@@ -18,6 +20,7 @@ var errNeedLogin = clog.Fatal(
 )
 
 func newClient() (*coder.Client, error) {
+	ctx := context.Background()
 	sessionToken, err := config.Session.Read()
 	if err != nil {
 		return nil, errNeedLogin
@@ -38,9 +41,7 @@ func newClient() (*coder.Client, error) {
 		Token:   sessionToken,
 	}
 
-	// Make sure we can make a request so the final
-	// error is more clean.
-	_, err = c.Me(context.Background())
+	apiVersion, err := c.APIVersion(ctx)
 	if err != nil {
 		var he *coder.HTTPError
 		if xerrors.As(err, &he) {
@@ -52,5 +53,14 @@ func newClient() (*coder.Client, error) {
 		return nil, err
 	}
 
+	if !version.VersionsMatch(apiVersion) {
+		clog.Log(clog.Warn(
+			"version mismatch detected",
+			fmt.Sprintf("coder-cli version: %s", version.Version),
+			fmt.Sprintf("Coder API version: %s", apiVersion), clog.BlankLine,
+			clog.Tipf("download the appropriate version here: https://github.com/cdr/coder-cli/releases"),
+		))
+	}
+
 	return c, nil
 }
diff --git a/internal/version/version.go b/internal/version/version.go
@@ -0,0 +1,18 @@
+package version
+
+import (
+	"strings"
+)
+
+// Version is populated at compile-time with the current coder-cli version.
+var Version string = "unknown"
+
+// VersionMatch compares the given APIVersion to the compile-time injected coder-cli version.
+func VersionsMatch(apiVersion string) bool {
+	withoutPatchRelease := strings.Split(Version, ".")
+	if len(withoutPatchRelease) < 3 {
+		return false
+	}
+	majorMinor := strings.Join(withoutPatchRelease[:len(withoutPatchRelease)-1], ".")
+	return strings.HasPrefix(strings.TrimPrefix(apiVersion, "v"), strings.TrimPrefix(majorMinor, "v"))
+}
diff --git a/internal/version/version_test.go b/internal/version/version_test.go
@@ -0,0 +1,29 @@
+package version
+
+import (
+	"testing"
+
+	"cdr.dev/slog/sloggers/slogtest/assert"
+)
+
+func TestVersion(t *testing.T) {
+	Version = "1.12.1"
+	match := VersionsMatch("1.12.2")
+	assert.True(t, "versions match", match)
+
+	Version = "v1.14.1"
+	match = VersionsMatch("1.15.2")
+	assert.True(t, "versions do not match", !match)
+
+	Version = "v1.15.4"
+	match = VersionsMatch("1.15.2")
+	assert.True(t, "versions do match", match)
+
+	Version = "1.15.4"
+	match = VersionsMatch("v1.15.2")
+	assert.True(t, "versions do match", match)
+
+	Version = "1.15.4"
+	match = VersionsMatch("v2.15.2")
+	assert.True(t, "versions do not match", !match)
+}