feat(jsonnet): allow other entrypoints (grafana#389)

So far, Tanka always evaluates `main.jsonnet` whatever directory it receives from the user. Going on, this is still supported and the default behavior.

When passed a plain file instead of a directory instead however, Tanka evaluates that file now, choosing the enclosing directory as the environments directory. 

This makes `tk show` and `tk eval` more lightweight, requiring only a single file, not a whole directory.

cmd/tk/tool.go

@@ -41,8 +41,11 @@ func jpathCmd() *cli.Command {
 			if err != nil {
 				return fmt.Errorf("Resolving JPATH: %s", err)
 			}
-
-			fmt.Println("main:", filepath.Join(base, "main.jsonnet"))
+			entrypoint, err := jpath.Entrypoint(base)
+			if err != nil {
+				return fmt.Errorf("Resolving JPATH: %s", err)
+			}
+			fmt.Println("main:", entrypoint)
 			fmt.Println("rootDir:", root)
 			fmt.Println("baseDir:", base)
 			fmt.Println("jpath:", path)

pkg/jsonnet/eval.go

@@ -1,8 +1,6 @@
 package jsonnet
 
 import (
-	"path/filepath"
-
 	jsonnet "github.com/google/go-jsonnet"
 	"github.com/pkg/errors"
 
@@ -60,7 +58,7 @@ func MakeVM(opts Opts) *jsonnet.VM {
 // result in JSON form. It disregards opts.ImportPaths in favor of automatically
 // resolving these according to the specified file.
 func EvaluateFile(jsonnetFile string, opts Opts) (string, error) {
-	jpath, _, _, err := jpath.Resolve(filepath.Dir(jsonnetFile))
+	jpath, _, _, err := jpath.Resolve(jsonnetFile)
 	if err != nil {
 		return "", errors.Wrap(err, "resolving import paths")
 	}
@@ -71,12 +69,12 @@ func EvaluateFile(jsonnetFile string, opts Opts) (string, error) {
 }
 
 // Evaluate renders the given jsonnet into a string
-func Evaluate(filename, data string, opts Opts) (string, error) {
-	jpath, _, _, err := jpath.Resolve(filepath.Dir(filename))
+func Evaluate(path, data string, opts Opts) (string, error) {
+	jpath, _, _, err := jpath.Resolve(path)
 	if err != nil {
 		return "", errors.Wrap(err, "resolving import paths")
 	}
 	opts.ImportPaths = jpath
 	vm := MakeVM(opts)
-	return vm.EvaluateAnonymousSnippet(filename, data)
+	return vm.EvaluateAnonymousSnippet(path, data)
 }

pkg/jsonnet/imports.go

@@ -26,9 +26,12 @@ func TransitiveImports(dir string) ([]string, error) {
 		return nil, err
 	}
 
-	mainFile := filepath.Join(dir, "main.jsonnet")
+	entrypoint, err := jpath.Entrypoint(dir)
+	if err != nil {
+		return nil, err
+	}
 
-	sonnet, err := ioutil.ReadFile(mainFile)
+	sonnet, err := ioutil.ReadFile(entrypoint)
 	if err != nil {
 		return nil, errors.Wrap(err, "opening file")
 	}
@@ -44,13 +47,13 @@ func TransitiveImports(dir string) ([]string, error) {
 		vm.NativeFunction(nf)
 	}
 
-	node, err := jsonnet.SnippetToAST("main.jsonnet", string(sonnet))
+	node, err := jsonnet.SnippetToAST(filepath.Base(entrypoint), string(sonnet))
 	if err != nil {
 		return nil, errors.Wrap(err, "creating Jsonnet AST")
 	}
 
 	imports := make(map[string]bool)
-	if err = importRecursive(imports, vm, node, "main.jsonnet"); err != nil {
+	if err = importRecursive(imports, vm, node, filepath.Base(entrypoint)); err != nil {
 		return nil, err
 	}
 
@@ -65,7 +68,7 @@ func TransitiveImports(dir string) ([]string, error) {
 		paths = append(paths, p)
 
 	}
-	paths = append(paths, mainFile)
+	paths = append(paths, entrypoint)
 
 	for i := range paths {
 		paths[i], _ = filepath.Rel(rootDir, paths[i])

pkg/jsonnet/jpath/jpath.go

@@ -8,12 +8,14 @@ import (
 	"runtime"
 )
 
+const DEFAULT_ENTRYPOINT = "main.jsonnet"
+
 var (
 	// ErrorNoRoot means no rootDir was found in the parents
 	ErrorNoRoot = errors.New("could not locate a tkrc.yaml or jsonnetfile.json in the parent directories, which is required to identify the project root.\nRefer to https://tanka.dev/directory-structure for more information")
 
 	// ErrorNoBase means no baseDir was found in the parents
-	ErrorNoBase = errors.New("could not locate a main.jsonnet in the parent directories, which is required as the entrypoint for the evaluation.\nRefer to https://tanka.dev/directory-structure for more information")
+	ErrorNoBase = errors.New("could not locate entrypoint (usually main.jsonnet) in the parent directories, which is required as the entrypoint for the evaluation.\nRefer to https://tanka.dev/directory-structure for more information")
 )
 
 // ErrorFileNotFound means that the searched file was not found
@@ -25,25 +27,25 @@ func (e ErrorFileNotFound) Error() string {
 	return e.filename + " not found"
 }
 
-// Resolve the given directory and resolves the jPath around it. This means it:
+// Resolve the given path and resolves the jPath around it. This means it:
 // - figures out the project root (the one with .jsonnetfile, vendor/ and lib/)
-// - figures out the environments base directory (the one with the main.jsonnet)
+// - figures out the environments base directory (usually the main.jsonnet)
 //
 // It then constructs a jPath with the base directory, vendor/ and lib/.
 // This results in predictable imports, as it doesn't matter whether the user called
 // called the command further down tree or not. A little bit like git.
-func Resolve(workdir string) (path []string, base, root string, err error) {
-	workdir, err = filepath.Abs(workdir)
+func Resolve(path string) (jpath []string, base, root string, err error) {
+	entrypoint, err := Entrypoint(path)
 	if err != nil {
 		return nil, "", "", err
 	}
 
-	root, err = FindRoot(workdir)
+	root, err = FindRoot(filepath.Dir(entrypoint))
 	if err != nil {
 		return nil, "", "", err
 	}
 
-	base, err = FindParentFile("main.jsonnet", workdir, root)
+	base, err = FindParentFile(filepath.Base(entrypoint), filepath.Dir(entrypoint), root)
 	if err != nil {
 		if _, ok := err.(ErrorFileNotFound); ok {
 			return nil, "", "", ErrorNoBase
@@ -113,3 +115,22 @@ func dirContainsFile(files []os.FileInfo, filename string) bool {
 	}
 	return false
 }
+
+func Entrypoint(path string) (string, error) {
+	filename := DEFAULT_ENTRYPOINT
+
+	entrypoint, err := filepath.Abs(path)
+	if err != nil {
+		return "", err
+	}
+
+	stat, err := os.Stat(entrypoint)
+	if err != nil {
+		return "", err
+	}
+	if !stat.IsDir() {
+		return entrypoint, nil
+	}
+
+	return filepath.Join(entrypoint, filename), nil
+}

pkg/tanka/parse.go

@@ -63,8 +63,8 @@ func (p *loaded) connect() (*kubernetes.Kubernetes, error) {
 }
 
 // load runs all processing stages described at the Processed type
-func load(dir string, opts Opts) (*loaded, error) {
-	raw, env, err := eval(dir, opts.JsonnetOpts)
+func load(path string, opts Opts) (*loaded, error) {
+	raw, env, err := eval(path, opts.JsonnetOpts)
 	if err != nil {
 		return nil, err
 	}
@@ -86,18 +86,13 @@ func load(dir string, opts Opts) (*loaded, error) {
 
 // eval runs all processing stages describe at the Processed type apart from
 // post-processing, thus returning the raw Jsonnet result.
-func eval(dir string, opts jsonnet.Opts) (raw interface{}, env *v1alpha1.Config, err error) {
-	_, baseDir, rootDir, err := jpath.Resolve(dir)
-	if err != nil {
-		return nil, nil, errors.Wrap(err, "resolving jpath")
-	}
-
-	env, err = parseSpec(baseDir, rootDir)
+func eval(path string, opts jsonnet.Opts) (raw interface{}, env *v1alpha1.Config, err error) {
+	env, err = parseSpec(path)
 	if err != nil {
 		return nil, nil, err
 	}
 
-	raw, err = evalJsonnet(baseDir, env, opts)
+	raw, err = evalJsonnet(path, env, opts)
 	if err != nil {
 		return nil, nil, errors.Wrap(err, "evaluating jsonnet")
 	}
@@ -107,7 +102,12 @@ func eval(dir string, opts jsonnet.Opts) (raw interface{}, env *v1alpha1.Config,
 
 // parseEnv parses the `spec.json` of the environment and returns a
 // *kubernetes.Kubernetes from it
-func parseSpec(baseDir, rootDir string) (*v1alpha1.Config, error) {
+func parseSpec(path string) (*v1alpha1.Config, error) {
+	_, baseDir, rootDir, err := jpath.Resolve(path)
+	if err != nil {
+		return nil, errors.Wrap(err, "resolving jpath")
+	}
+
 	// name of the environment: relative path from rootDir
 	name, _ := filepath.Rel(rootDir, baseDir)
 
@@ -129,9 +129,8 @@ func parseSpec(baseDir, rootDir string) (*v1alpha1.Config, error) {
 	return config, nil
 }
 
-// evalJsonnet evaluates the jsonnet environment at the given directory starting with
-// `main.jsonnet`
-func evalJsonnet(baseDir string, env *v1alpha1.Config, opts jsonnet.Opts) (interface{}, error) {
+// evalJsonnet evaluates the jsonnet environment at the given path
+func evalJsonnet(path string, env *v1alpha1.Config, opts jsonnet.Opts) (interface{}, error) {
 	// make env spec accessible from Jsonnet
 	jsonEnv, err := json.Marshal(env)
 	if err != nil {
@@ -141,15 +140,19 @@ func evalJsonnet(baseDir string, env *v1alpha1.Config, opts jsonnet.Opts) (inter
 
 	// evaluate Jsonnet
 	var raw string
-	mainFile := filepath.Join(baseDir, "main.jsonnet")
+	entrypoint, err := jpath.Entrypoint(path)
+	if err != nil {
+		return nil, err
+	}
+
 	if opts.EvalPattern != "" {
-		evalScript := fmt.Sprintf("(import '%s').%s", mainFile, opts.EvalPattern)
-		raw, err = jsonnet.Evaluate(mainFile, evalScript, opts)
+		evalScript := fmt.Sprintf("(import '%s').%s", entrypoint, opts.EvalPattern)
+		raw, err = jsonnet.Evaluate(entrypoint, evalScript, opts)
 		if err != nil {
 			return nil, err
 		}
 	} else {
-		raw, err = jsonnet.EvaluateFile(mainFile, opts)
+		raw, err = jsonnet.EvaluateFile(entrypoint, opts)
 		if err != nil {
 			return nil, err
 		}