feat(docker): Honor the host specified in current docker context

dive/image/docker/docker_host_unix.go

@@ -0,0 +1,7 @@
+//go:build !windows
+
+package docker
+
+const (
+	defaultDockerHost = "unix:///var/run/docker.sock"
+)

dive/image/docker/docker_host_windows.go

@@ -0,0 +1,5 @@
+package docker
+
+const (
+	defaultDockerHost = "npipe:////.pipe/docker_engine"
+)

dive/image/docker/engine_resolver.go

@@ -7,7 +7,10 @@ import (
 	"os"
 	"strings"
 
+	cliconfig "github.com/docker/cli/cli/config"
 	"github.com/docker/cli/cli/connhelper"
+	ddocker "github.com/docker/cli/cli/context/docker"
+	ctxstore "github.com/docker/cli/cli/context/store"
 	"github.com/docker/docker/client"
 	"golang.org/x/net/context"
 
@@ -49,8 +52,12 @@ func (r *engineResolver) fetchArchive(id string) (io.ReadCloser, error) {
 	// pull the engineResolver if it does not exist
 	ctx := context.Background()
 
-	host := os.Getenv("DOCKER_HOST")
-	var clientOpts []client.Opt
+	host, err := determineDockerHost()
+	if err != nil {
+		fmt.Printf("> could not determine docker host: %v\n", err)
+	}
+	clientOpts := []client.Opt{client.FromEnv}
+	clientOpts = append(clientOpts, client.WithHost(host))
 
 	switch strings.Split(host, ":")[0] {
 	case "ssh":
@@ -66,16 +73,15 @@ func (r *engineResolver) fetchArchive(id string) (io.ReadCloser, error) {
 			}
 			return client.WithHTTPClient(httpClient)(c)
 		})
-		clientOpts = append(clientOpts, client.WithHost(helper.Host))
+
+		clientOpts = append(clientOpts, client.WithHost(host))
 		clientOpts = append(clientOpts, client.WithDialContext(helper.Dialer))
 
 	default:
 
 		if os.Getenv("DOCKER_TLS_VERIFY") != "" && os.Getenv("DOCKER_CERT_PATH") == "" {
 			os.Setenv("DOCKER_CERT_PATH", "~/.docker")
 		}
-
-		clientOpts = append(clientOpts, client.FromEnv)
 	}
 
 	clientOpts = append(clientOpts, client.WithAPIVersionNegotiation())
@@ -100,3 +106,67 @@ func (r *engineResolver) fetchArchive(id string) (io.ReadCloser, error) {
 
 	return readCloser, nil
 }
+
+// determineDockerHost tries to the determine the docker host that we should connect to
+// in the following order of decreasing precedence:
+//   - value of "DOCKER_HOST" environment variable
+//   - host retrieved from the current context (specified via DOCKER_CONTEXT)
+//   - "default docker host" for the host operating system, otherwise
+func determineDockerHost() (string, error) {
+	// If the docker host is explicitly set via the "DOCKER_HOST" environment variable,
+	// then its a no-brainer :shrug:
+	if os.Getenv("DOCKER_HOST") != "" {
+		return os.Getenv("DOCKER_HOST"), nil
+	}
+
+	currentContext := os.Getenv("DOCKER_CONTEXT")
+	if currentContext == "" {
+		dockerConfigDir := cliconfig.Dir()
+		if _, err := os.Stat(dockerConfigDir); err != nil {
+			return "", err
+		}
+		cf, err := cliconfig.Load(dockerConfigDir)
+		if err != nil {
+			return "", err
+		}
+		currentContext = cf.CurrentContext
+	}
+
+	if currentContext == "" {
+		// If a docker context is neither specified via the "DOCKER_CONTEXT" environment variable nor via the
+		// $HOME/.docker/config file, then we fall back to connecting to the "default docker host" meant for
+		// the host operating system.
+		return defaultDockerHost, nil
+	}
+
+	storeConfig := ctxstore.NewConfig(
+		func() interface{} { return &ddocker.EndpointMeta{} },
+		ctxstore.EndpointTypeGetter(ddocker.DockerEndpoint, func() interface{} { return &ddocker.EndpointMeta{} }),
+	)
+
+	st := ctxstore.New(cliconfig.ContextStoreDir(), storeConfig)
+	md, err := st.GetMetadata(currentContext)
+	if err != nil {
+		return "", err
+	}
+	dockerEP, ok := md.Endpoints[ddocker.DockerEndpoint]
+	if !ok {
+		return "", err
+	}
+	dockerEPMeta, ok := dockerEP.(ddocker.EndpointMeta)
+	if !ok {
+		return "", fmt.Errorf("expected docker.EndpointMeta, got %T", dockerEP)
+	}
+
+	if dockerEPMeta.Host != "" {
+		return dockerEPMeta.Host, nil
+	}
+
+	// We might end up here, if the context was created with the `host` set to an empty value (i.e. '').
+	// For example:
+	// ```sh
+	// docker context create foo --docker "host="
+	// ```
+	// In such scenario, we mimic the `docker` cli and try to connect to the "default docker host".
+	return defaultDockerHost, nil
+}

go.mod

@@ -6,8 +6,8 @@ require (
 	github.com/awesome-gocui/gocui v1.1.0
 	github.com/awesome-gocui/keybinding v1.0.1-0.20190805183143-864552bd36b7
 	github.com/cespare/xxhash v1.1.0
-	github.com/docker/cli v0.0.0-20190906153656-016a3232168d
-	github.com/docker/docker v24.0.2+incompatible
+	github.com/docker/cli v20.10.15+incompatible
+	github.com/docker/docker v20.10.15+incompatible
 	github.com/dustin/go-humanize v1.0.0
 	github.com/fatih/color v1.7.0
 	github.com/google/uuid v1.1.1
@@ -26,9 +26,11 @@ require (
 require (
 	github.com/Microsoft/go-winio v0.4.14 // indirect
 	github.com/docker/distribution v2.8.2+incompatible // indirect
+	github.com/docker/docker-credential-helpers v0.8.0 // indirect
 	github.com/docker/go-connections v0.4.0 // indirect
 	github.com/docker/go-units v0.4.0 // indirect
 	github.com/fsnotify/fsnotify v1.4.7 // indirect
+	github.com/fvbommel/sortorder v1.1.0 // indirect
 	github.com/gdamore/encoding v1.0.0 // indirect
 	github.com/gdamore/tcell/v2 v2.4.0 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
@@ -56,6 +58,5 @@ require (
 	golang.org/x/term v0.9.0 // indirect
 	golang.org/x/text v0.10.0 // indirect
 	gopkg.in/yaml.v2 v2.2.8 // indirect
-	gotest.tools v2.2.0+incompatible // indirect
 	gotest.tools/v3 v3.5.0 // indirect
 )

go.sum

@@ -32,12 +32,14 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dgrijalva/jwt-go v3.2.0+incompatible/go.mod h1:E3ru+11k8xSBh+hMPgOLZmtrrCbhqsmaPHjLKYnJCaQ=
 github.com/dgryski/go-sip13 v0.0.0-20181026042036-e10d5fee7954/go.mod h1:vAd38F8PWV+bWy6jNmig1y/TA+kYO4g3RSRF0IAv0no=
-github.com/docker/cli v0.0.0-20190906153656-016a3232168d h1:gwX/88xJZfxZV1yjhhuQpWTmEgJis7/XGCVu3iDIZYU=
-github.com/docker/cli v0.0.0-20190906153656-016a3232168d/go.mod h1:JLrzqnKDaYBop7H2jaqPtU4hHvMKP+vjCwu2uszcLI8=
+github.com/docker/cli v20.10.15+incompatible h1:HGO75iIgpyuG1m0hw0Kp7hY5o7XELmY1rsT9gIptOSU=
+github.com/docker/cli v20.10.15+incompatible/go.mod h1:JLrzqnKDaYBop7H2jaqPtU4hHvMKP+vjCwu2uszcLI8=
 github.com/docker/distribution v2.8.2+incompatible h1:T3de5rq0dB1j30rp0sA2rER+m322EBzniBPB6ZIzuh8=
 github.com/docker/distribution v2.8.2+incompatible/go.mod h1:J2gT2udsDAN96Uj4KfcMRqY0/ypR+oyYUYmja8H+y+w=
-github.com/docker/docker v24.0.2+incompatible h1:eATx+oLz9WdNVkQrr0qjQ8HvRJ4bOOxfzEo8R+dA3cg=
-github.com/docker/docker v24.0.2+incompatible/go.mod h1:eEKB0N0r5NX/I1kEveEz05bcu8tLC/8azJZsviup8Sk=
+github.com/docker/docker v20.10.15+incompatible h1:dk9FewY/9Xwm4ay/HViEEHSQuM/kL4F+JaG6GQdgmGo=
+github.com/docker/docker v20.10.15+incompatible/go.mod h1:eEKB0N0r5NX/I1kEveEz05bcu8tLC/8azJZsviup8Sk=
+github.com/docker/docker-credential-helpers v0.8.0 h1:YQFtbBQb4VrpoPxhFuzEBPQ9E16qz5SpHLS+uswaCp8=
+github.com/docker/docker-credential-helpers v0.8.0/go.mod h1:UGFXcuoQ5TxPiB54nHOZ32AWRqQdECoh/Mg0AlEYb40=
 github.com/docker/go-connections v0.4.0 h1:El9xVISelRB7BuFusrZozjnkIM5YnzCViNKohAFqRJQ=
 github.com/docker/go-connections v0.4.0/go.mod h1:Gbd7IOopHjR8Iph03tsViu4nIes5XhDvyHbTtUxmeec=
 github.com/docker/go-units v0.4.0 h1:3uh0PgVws3nIA0Q+MwDC8yjEPf9zjRfZZWXZYDct3Tw=
@@ -48,6 +50,8 @@ github.com/fatih/color v1.7.0 h1:DkWD4oS2D8LGGgTQ6IvwJJXSL5Vp2ffcQg58nFV38Ys=
 github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5KwzbycvMj4=
 github.com/fsnotify/fsnotify v1.4.7 h1:IXs+QLmnXW2CcXuY+8Mzv/fWEsPGWxqefPtCP5CnV9I=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
+github.com/fvbommel/sortorder v1.1.0 h1:fUmoe+HLsBTctBDoaBwpQo5N+nrCp8g/BjKb/6ZQmYw=
+github.com/fvbommel/sortorder v1.1.0/go.mod h1:uk88iVf1ovNn1iLfgUVU2F9o5eO30ui720w+kxuqRs0=
 github.com/gdamore/encoding v1.0.0 h1:+7OoQ1Bc6eTm5niUzBa0Ctsh6JbMW6Ra+YNuAtDBdko=
 github.com/gdamore/encoding v1.0.0/go.mod h1:alR0ol34c49FCSBLjhosxzcPHQbf2trDkoo5dl+VrEg=
 github.com/gdamore/tcell/v2 v2.4.0 h1:W6dxJEmaxYvhICFoTY3WrLLEXsQ11SaFnKGVEXW57KM=
@@ -267,8 +271,6 @@ gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.8 h1:obN1ZagJSUGI0Ek/LBmuj4SNLPfIny3KsKFopxRdj10=
 gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gotest.tools v2.2.0+incompatible h1:VsBPFP1AI068pPrMxtb/S8Zkgf9xEmTLJjfM+P5UIEo=
-gotest.tools v2.2.0+incompatible/go.mod h1:DsYFclhRJ6vuDpmuTbkuFWG+y2sxOXAzmJt81HFBacw=
 gotest.tools/v3 v3.5.0 h1:Ljk6PdHdOhAb5aDMWXjDLMMhph+BpztA4v1QdqEW2eY=
 gotest.tools/v3 v3.5.0/go.mod h1:isy3WKz7GK6uNw/sbHzfKBLvlvXwUyV06n6brMxxopU=
 honnef.co/go/tools v0.0.0-20190102054323-c2f93a96b099/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=