bundle: report a directory at a state path as "not a file"

The workspace exports a directory as a ZIP archive even with direct_download=true, so since
the state read stopped calling get-status first, a directory there failed with a JSON parse
error on the archive. Recognize the ZIP header and say what is wrong. The test server now
exports directories the same way.

Co-authored-by: Isaac <no-reply@databricks.com>

Author: denik

acceptance/bundle/state/directory_at_state_path/databricks.yml.tmpl

@@ -0,0 +1,7 @@
+bundle:
+  name: directory-at-state-path-$UNIQUE_NAME
+
+resources:
+  jobs:
+    foo:
+      name: foo

acceptance/bundle/state/directory_at_state_path/out.test.toml

@@ -0,0 +1,2 @@
+Cloud = true
+EnvMatrix.DMS = ["", "true"]

acceptance/bundle/state/directory_at_state_path/output.txt

@@ -0,0 +1,4 @@
+
+>>> musterr [CLI] bundle plan
+Error: reading resources.json: not a file: the workspace has a directory at this path
+

acceptance/bundle/state/directory_at_state_path/script

@@ -0,0 +1,14 @@
+envsubst < databricks.yml.tmpl > databricks.yml
+
+# Something else created a directory where the CLI keeps its state file.
+state_path=$($CLI bundle validate -o json | jq -r .workspace.state_path)
+# MSYS_NO_PATHCONV stops Git Bash on Windows from rewriting the /Workspace/... argument into a local path.
+MSYS_NO_PATHCONV=1 $CLI workspace mkdirs "$state_path/resources.json"
+
+cleanup() {
+    MSYS_NO_PATHCONV=1 $CLI workspace delete --recursive "$($CLI bundle validate -o json | jq -r .workspace.root_path)"
+    rm -f "$OUT_REQUESTS"
+}
+trap cleanup EXIT
+
+trace musterr $CLI bundle plan

acceptance/bundle/state/directory_at_state_path/test.toml

@@ -0,0 +1,2 @@
+# Exercises the real workspace's export of a directory, which returns a ZIP archive.
+Cloud = true

bundle/statemgmt/state_pull.go

@@ -1,6 +1,7 @@
 package statemgmt
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"errors"
@@ -26,6 +27,9 @@ import (
 
 type AlwaysPull bool
 
+// zipMagic starts every ZIP archive; a state file is JSON and never does.
+var zipMagic = []byte("PK\x03\x04")
+
 type StateDesc struct {
 	Serial   int                 `json:"serial"`
 	Lineage  string              `json:"lineage"`
@@ -113,6 +117,11 @@ func _filerRead(ctx context.Context, f filer.Filer, path string) (*StateDesc, er
 	state := &StateDesc{}
 	err = json.Unmarshal(content, state)
 	if err != nil {
+		// The workspace exports a directory as a ZIP archive rather than failing, so a directory
+		// at the state path reads fine and only shows up here.
+		if bytes.HasPrefix(content, zipMagic) {
+			return nil, errors.New("not a file: the workspace has a directory at this path")
+		}
 		return nil, fmt.Errorf("parsing state: %w", err)
 	}
 

libs/testserver/fake_workspace.go

@@ -845,9 +845,27 @@ func (s *FakeWorkspace) WorkspaceMkdirs(request workspace.Mkdirs) {
 
 func (s *FakeWorkspace) WorkspaceExport(path string) []byte {
 	defer s.LockUnlock()()
+	if _, isDir := s.directories[path]; isDir {
+		return exportDirectory(path)
+	}
 	return s.files[path].Data
 }
 
+// exportDirectory mimics the real API, which exports a directory as a ZIP archive even with
+// direct_download=true. Only the directory's own entry is included: callers just need to see
+// that they got an archive rather than a file.
+func exportDirectory(dirPath string) []byte {
+	var buf bytes.Buffer
+	zw := zip.NewWriter(&buf)
+	if _, err := zw.Create(path.Base(dirPath) + "/"); err != nil {
+		panic(err)
+	}
+	if err := zw.Close(); err != nil {
+		panic(err)
+	}
+	return buf.Bytes()
+}
+
 // WorkspaceDelete implements POST /api/2.0/workspace/delete. As in the real API, a
 // non-recursive delete of a directory that still has children fails instead of removing
 // it, which is what lets a caller delete a directory only if it is empty.