Test whether a backend can be run at all (#190)

* Dart "pub" command is now a subcommand of "dart"

* Adding IsAvailable checks

* Providing basic implementations of IsAvailable for known binaries

internal/api/types.go

@@ -171,6 +171,9 @@ type LanguageBackend struct {
 	// Poetry.
 	Lockfile string
 
+	// Check to see if we think we can run at all
+	IsAvailable func() bool
+
 	// List of filename globs that match against files written in
 	// this programming language, e.g. "*.py" for Python. These
 	// should not include any slashes, because they may be matched
@@ -350,6 +353,7 @@ func (b *LanguageBackend) Setup() {
 		"missing Info":                     b.Info == nil,
 		"missing Add":                      b.Add == nil,
 		"missing Remove":                   b.Remove == nil,
+		"missing IsAvailable":              b.IsAvailable == nil,
 		// The lock method should be unimplemented if
 		// and only if builds are not reproducible.
 		"either implement Lock or mark QuirksIsNotReproducible": ((b.Lock == nil) != b.QuirksIsNotReproducible()),

internal/backends/backends.go

@@ -123,13 +123,18 @@ func GetBackend(ctx context.Context, language string) api.LanguageBackend {
 	return backends[0]
 }
 
+type BackendInfo struct {
+	Name      string
+	Available bool
+}
+
 // GetBackendNames returns a slice of the canonical names (e.g.
 // python-python3-poetry, not just python3) for all the backends
 // listed in languageBackends.
-func GetBackendNames() []string {
-	backendNames := []string{}
+func GetBackendNames() []BackendInfo {
+	var backendNames []BackendInfo
 	for _, b := range languageBackends {
-		backendNames = append(backendNames, b.Name)
+		backendNames = append(backendNames, BackendInfo{Name: b.Name, Available: b.IsAvailable()})
 	}
 	return backendNames
 }

internal/backends/dart/dart.go

@@ -10,6 +10,7 @@ import (
 	"net/http"
 	"net/url"
 	"os"
+	"os/exec"
 	"path"
 	"runtime"
 
@@ -20,6 +21,11 @@ import (
 	"gopkg.in/yaml.v2"
 )
 
+func dartIsAvailable() bool {
+	_, err := exec.LookPath("dart")
+	return err == nil
+}
+
 // getPubBaseUrl returns pub.dartlang.org (the primary API endpoint for pub.dev)
 // or a local override if set.
 func getPubBaseURL() string {
@@ -298,6 +304,7 @@ var DartPubBackend = api.LanguageBackend{
 	Name:             "dart-pub",
 	Specfile:         "pubspec.yaml",
 	Lockfile:         "pubspec.lock",
+	IsAvailable:      dartIsAvailable,
 	FilenamePatterns: []string{"*.dart"},
 	Quirks:           api.QuirksLockAlsoInstalls,
 	GetPackageDir:    dartGetPackageDir,
@@ -309,13 +316,13 @@ var DartPubBackend = api.LanguageBackend{
 		//nolint:ineffassign,wastedassign,staticcheck
 		span, ctx := tracer.StartSpanFromContext(ctx, "pub get")
 		defer span.Finish()
-		util.RunCmd([]string{"pub", "get"})
+		util.RunCmd([]string{"dart", "pub", "get"})
 	},
 	Install: func(ctx context.Context) {
 		//nolint:ineffassign,wastedassign,staticcheck
 		span, ctx := tracer.StartSpanFromContext(ctx, "pub get")
 		defer span.Finish()
-		util.RunCmd([]string{"pub", "get"})
+		util.RunCmd([]string{"dart", "pub", "get"})
 	},
 	ListSpecfile:                       dartListPubspecYaml,
 	ListLockfile:                       dartListPubspecLock,

internal/backends/dotnet/dotnet.go

@@ -3,17 +3,24 @@ package dotnet
 
 import (
 	"context"
+	"os/exec"
 
 	"github.com/replit/upm/internal/api"
 	"github.com/replit/upm/internal/nix"
 	"github.com/replit/upm/internal/util"
 )
 
+func dotnetIsAvailable() bool {
+	_, err := exec.LookPath("dotnet")
+	return err == nil
+}
+
 // DotNetBackend is the UPM language backend .NET languages with support for C#
 var DotNetBackend = api.LanguageBackend{
 	Name:             "dotnet",
 	Specfile:         findSpecFile(),
 	Lockfile:         lockFileName,
+	IsAvailable:      dotnetIsAvailable,
 	FilenamePatterns: []string{"*.cs", "*.csproj", "*.fs", "*.fsproj"},
 	Remove: func(ctx context.Context, pkgs map[api.PkgName]bool) {
 		removePackages(ctx, pkgs, findSpecFile(), util.RunCmd)

internal/backends/elisp/elisp.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"regexp"
 	"strings"
@@ -19,11 +20,20 @@ import (
 // elispPatterns is the FilenamePatterns value for ElispBackend.
 var elispPatterns = []string{"*.el"}
 
+func elispCaskIsAvailable() bool {
+	_, err := exec.LookPath("emacs")
+	if err == nil {
+		_, err = exec.LookPath("cask")
+	}
+	return err == nil
+}
+
 // ElispBackend is the UPM language backend for Emacs Lisp using Cask.
 var ElispBackend = api.LanguageBackend{
 	Name:             "elisp-cask",
 	Specfile:         "Cask",
 	Lockfile:         "packages.txt",
+	IsAvailable:      elispCaskIsAvailable,
 	FilenamePatterns: elispPatterns,
 	Quirks:           api.QuirksNotReproducible,
 	GetPackageDir: func() string {

internal/backends/java/java.go

@@ -6,6 +6,7 @@ import (
 	"encoding/xml"
 	"fmt"
 	"os"
+	"os/exec"
 	"regexp"
 
 	"github.com/replit/upm/internal/api"
@@ -115,6 +116,11 @@ func readProjectOrMakeEmpty(path string) Project {
 
 const pomdotxml = "pom.xml"
 
+func isAvailable() bool {
+	_, err := exec.LookPath("mvn")
+	return err == nil
+}
+
 func addPackages(ctx context.Context, pkgs map[api.PkgName]api.PkgSpec, projectName string) {
 	//nolint:ineffassign,wastedassign,staticcheck
 	span, ctx := tracer.StartSpanFromContext(ctx, "Java add package")
@@ -302,6 +308,7 @@ var JavaBackend = api.LanguageBackend{
 	Name:             "java-maven",
 	Specfile:         pomdotxml,
 	Lockfile:         pomdotxml,
+	IsAvailable:      isAvailable,
 	FilenamePatterns: javaPatterns,
 	Quirks:           api.QuirksAddRemoveAlsoLocks,
 	GetPackageDir: func() string {

internal/backends/nodejs/nodejs.go

@@ -195,6 +195,26 @@ type packageLockJSON struct {
 // nodejsPatterns is the FilenamePatterns value for NodejsBackend.
 var nodejsPatterns = []string{"*.js", "*.ts", "*.jsx", "*.tsx", "*.mjs", "*.cjs"}
 
+func bunIsAvailable() bool {
+	_, err := exec.LookPath("bun")
+	return err == nil
+}
+
+func pnpmIsAvailable() bool {
+	_, err := exec.LookPath("pnpm")
+	return err == nil
+}
+
+func yarnIsAvailable() bool {
+	_, err := exec.LookPath("yarn")
+	return err == nil
+}
+
+func npmIsAvailable() bool {
+	_, err := exec.LookPath("npm")
+	return err == nil
+}
+
 // nodejsSearch implements Search for nodejs-yarn, nodejs-pnpm and nodejs-npm.
 func nodejsSearch(query string) []api.PkgInfo {
 	// Special case: if search query is only one character, the
@@ -372,6 +392,7 @@ var NodejsYarnBackend = api.LanguageBackend{
 	Name:             "nodejs-yarn",
 	Specfile:         "package.json",
 	Lockfile:         "yarn.lock",
+	IsAvailable:      yarnIsAvailable,
 	FilenamePatterns: nodejsPatterns,
 	Quirks: api.QuirksAddRemoveAlsoLocks |
 		api.QuirksAddRemoveAlsoInstalls |
@@ -449,6 +470,7 @@ var NodejsPNPMBackend = api.LanguageBackend{
 	Name:             "nodejs-pnpm",
 	Specfile:         "package.json",
 	Lockfile:         "pnpm-lock.yaml",
+	IsAvailable:      pnpmIsAvailable,
 	FilenamePatterns: nodejsPatterns,
 	Quirks: api.QuirksAddRemoveAlsoLocks |
 		api.QuirksAddRemoveAlsoInstalls |
@@ -542,6 +564,7 @@ var NodejsNPMBackend = api.LanguageBackend{
 	Name:             "nodejs-npm",
 	Specfile:         "package.json",
 	Lockfile:         "package-lock.json",
+	IsAvailable:      npmIsAvailable,
 	FilenamePatterns: nodejsPatterns,
 	Quirks: api.QuirksAddRemoveAlsoLocks |
 		api.QuirksAddRemoveAlsoInstalls |
@@ -624,6 +647,7 @@ var BunBackend = api.LanguageBackend{
 	Name:             "bun",
 	Specfile:         "package.json",
 	Lockfile:         "bun.lockb",
+	IsAvailable:      bunIsAvailable,
 	FilenamePatterns: nodejsPatterns,
 	Quirks: api.QuirksAddRemoveAlsoLocks |
 		api.QuirksAddRemoveAlsoInstalls |

internal/backends/php/php.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"net/url"
 	"os"
+	"os/exec"
 	"strings"
 
 	"github.com/replit/upm/internal/api"
@@ -63,6 +64,11 @@ type authors struct {
 	Email string `json:"email"`
 }
 
+func composerIsAvailable() bool {
+	_, err := exec.LookPath("composer")
+	return err == nil
+}
+
 func search(query string) []api.PkgInfo {
 	endpoint := "https://packagist.org/search.json?q=" + url.QueryEscape(query)
 	resp, err := api.HttpClient.Get(endpoint)
@@ -227,6 +233,7 @@ var PhpComposerBackend = api.LanguageBackend{
 	Name:             "php-composer",
 	Specfile:         "composer.json",
 	Lockfile:         "composer.lock",
+	IsAvailable:      composerIsAvailable,
 	FilenamePatterns: []string{"*.php"},
 	Quirks:           api.QuirksAddRemoveAlsoLocks | api.QuirksAddRemoveAlsoInstalls,
 	GetPackageDir: func() string {

internal/backends/python/python.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"os/exec"
 	"regexp"
 	"strings"
 
@@ -68,6 +69,16 @@ type poetryLock struct {
 	} `json:"package"`
 }
 
+func pipIsAvailable() bool {
+	_, err := exec.LookPath("pip")
+	return err == nil
+}
+
+func poetryIsAvailable() bool {
+	_, err := exec.LookPath("poetry")
+	return err == nil
+}
+
 // normalizeSpec returns the version string from a Poetry spec, or the
 // empty string. The Poetry spec may be either a string or a
 // map[string]interface{} with a "version" key that is a string. If
@@ -199,6 +210,7 @@ func makePythonPoetryBackend(python string) api.LanguageBackend {
 		Alias:            "python-python3-poetry",
 		Specfile:         "pyproject.toml",
 		Lockfile:         "poetry.lock",
+		IsAvailable:      poetryIsAvailable,
 		FilenamePatterns: []string{"*.py"},
 		Quirks: api.QuirksAddRemoveAlsoLocks |
 			api.QuirksAddRemoveAlsoInstalls,
@@ -323,6 +335,7 @@ func makePythonPipBackend(python string) api.LanguageBackend {
 	b := api.LanguageBackend{
 		Name:                 "python3-pip",
 		Specfile:             "requirements.txt",
+		IsAvailable:          pipIsAvailable,
 		Alias:                "python-python3-pip",
 		FilenamePatterns:     []string{"*.py"},
 		Quirks:               api.QuirksAddRemoveAlsoInstalls | api.QuirksNotReproducible,

internal/backends/rlang/rlang.go

@@ -3,6 +3,7 @@ package rlang
 import (
 	"context"
 	"os"
+	"os/exec"
 	"path"
 	"regexp"
 	"strings"
@@ -12,6 +13,11 @@ import (
 	"github.com/replit/upm/internal/util"
 )
 
+func rIsAvailable() bool {
+	_, err := exec.LookPath("R")
+	return err == nil
+}
+
 func getImports(imports string) []string {
 	return regexp.MustCompile(`[a-zA-Z_]\w*`).FindAllString(imports, -1)
 }
@@ -81,6 +87,7 @@ var RlangBackend = api.LanguageBackend{
 	Name:             "rlang",
 	Specfile:         "Rconfig.json",
 	Lockfile:         "Rconfig.lock.json",
+	IsAvailable:      rIsAvailable,
 	FilenamePatterns: []string{"*.r", "*.R"},
 	Quirks:           api.QuirksNone,
 	GetPackageDir:    getRPkgDir,

internal/backends/ruby/ruby.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"net/url"
 	"os"
+	"os/exec"
 	"strings"
 
 	"github.com/replit/upm/internal/api"
@@ -33,6 +34,11 @@ type rubygemsInfo struct {
 	Version          string   `json:"version"`
 }
 
+func bundlerIsAvailable() bool {
+	_, err := exec.LookPath("bundle")
+	return err == nil
+}
+
 // getPath returns the appropriate --path for 'bundle install'. This
 // will normally be '.bundle' (in the current directory), but may
 // instead be the empty string, indicating that no --path argument
@@ -67,6 +73,7 @@ var RubyBackend = api.LanguageBackend{
 	Name:             "ruby-bundler",
 	Specfile:         "Gemfile",
 	Lockfile:         "Gemfile.lock",
+	IsAvailable:      bundlerIsAvailable,
 	FilenamePatterns: []string{"*.rb"},
 	Quirks:           api.QuirksAddRemoveAlsoLocks,
 	GetPackageDir: func() string {

internal/backends/rust/rust.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"net/url"
 	"os"
+	"os/exec"
 
 	"github.com/BurntSushi/toml"
 	"github.com/replit/upm/internal/api"
@@ -81,6 +82,11 @@ func (c *crateInfoResult) toPkgInfo() api.PkgInfo {
 	}
 }
 
+func cargoIsAvailable() bool {
+	_, err := exec.LookPath("cargo")
+	return err == nil
+}
+
 func search(query string) []api.PkgInfo {
 	endpoint := "https://crates.io/api/v1/crates"
 	path := "?q=" + url.QueryEscape(query)
@@ -224,6 +230,7 @@ var RustBackend = api.LanguageBackend{
 	Name:             "rust",
 	Specfile:         "Cargo.toml",
 	Lockfile:         "Cargo.lock",
+	IsAvailable:      cargoIsAvailable,
 	FilenamePatterns: []string{"*.rs"},
 	GetPackageDir: func() string {
 		return "target"

internal/cli/cmds.go

@@ -49,8 +49,12 @@ func runWhichLanguage(language string) {
 
 // runListLanguages implements 'upm list-languages'.
 func runListLanguages() {
-	for _, backendName := range backends.GetBackendNames() {
-		fmt.Println(backendName)
+	for _, info := range backends.GetBackendNames() {
+		if info.Available {
+			fmt.Println(info.Name)
+		} else {
+			fmt.Println(info.Name + "  (unavailable)")
+		}
 	}
 }