Do not validate .model.json files with no content/whitespace only (#420)

* Ignore empty/whitespace-only model.json files

* Ignore no return value from model.json files during snapshot

* Use str::from_utf8 instead of String::from_utf8

* Revert "Ignore no return value from model.json files during snapshot"

This reverts commit 0aef16e30a.

* Add test for empty .model.json files

* Change empty .model.json check method

Co-authored-by: Lucien Greathouse <me@lpghatguy.com>

* Format code with cargo fmt

* Use raw string instead

Co-authored-by: Lucien Greathouse <me@lpghatguy.com>

rojo-test/serve-test-snapshots/end_to_end__tests__serve__empty_json_model_all-2.snap

@@ -0,0 +1,28 @@
+---
+source: tests/tests/serve.rs
+expression: "read_response.intern_and_redact(&mut redactions, root_id)"
+
+---
+instances:
+  id-2:
+    Children:
+      - id-3
+    ClassName: Folder
+    Id: id-2
+    Metadata:
+      ignoreUnknownInstances: false
+    Name: empty_folder
+    Parent: "00000000000000000000000000000000"
+    Properties: {}
+  id-3:
+    Children: []
+    ClassName: Model
+    Id: id-3
+    Metadata:
+      ignoreUnknownInstances: false
+    Name: test
+    Parent: id-2
+    Properties: {}
+messageCursor: 1
+sessionId: id-1
+

rojo-test/serve-test-snapshots/end_to_end__tests__serve__empty_json_model_all.snap

@@ -0,0 +1,18 @@
+---
+source: tests/tests/serve.rs
+expression: "read_response.intern_and_redact(&mut redactions, root_id)"
+
+---
+instances:
+  id-2:
+    Children: []
+    ClassName: Folder
+    Id: id-2
+    Metadata:
+      ignoreUnknownInstances: false
+    Name: empty_folder
+    Parent: "00000000000000000000000000000000"
+    Properties: {}
+messageCursor: 0
+sessionId: id-1
+

rojo-test/serve-test-snapshots/end_to_end__tests__serve__empty_json_model_info.snap

@@ -0,0 +1,14 @@
+---
+source: tests/tests/serve.rs
+expression: redactions.redacted_yaml(info)
+
+---
+expectedPlaceIds: ~
+gameId: ~
+placeId: ~
+projectName: empty_folder
+protocolVersion: 4
+rootInstanceId: id-2
+serverVersion: "[server-version]"
+sessionId: id-1
+

rojo-test/serve-test-snapshots/end_to_end__tests__serve__empty_json_model_subscribe.snap

@@ -0,0 +1,21 @@
+---
+source: tests/tests/serve.rs
+expression: "subscribe_response.intern_and_redact(&mut redactions, ())"
+
+---
+messageCursor: 1
+messages:
+  - added:
+      id-3:
+        Children: []
+        ClassName: Model
+        Id: id-3
+        Metadata:
+          ignoreUnknownInstances: false
+        Name: test
+        Parent: id-2
+        Properties: {}
+    removed: []
+    updated: []
+sessionId: id-1
+

rojo-test/serve-tests/empty_json_model/default.project.json

@@ -0,0 +1,6 @@
+{
+  "name": "empty_folder",
+  "tree": {
+    "$path": "src"
+  }
+}

src/snapshot_middleware/json_model.rs

@@ -1,4 +1,4 @@
-use std::{borrow::Cow, collections::HashMap, path::Path};
+use std::{borrow::Cow, collections::HashMap, path::Path, str};
 
 use anyhow::Context;
 use memofs::Vfs;
@@ -18,7 +18,14 @@ pub fn snapshot_json_model(
     instance_name: &str,
 ) -> SnapshotInstanceResult {
     let contents = vfs.read(path)?;
-    let instance: JsonModel = serde_json::from_slice(&contents)
+    let contents_str = str::from_utf8(&contents)
+        .with_context(|| format!("File was not valid UTF-8: {}", path.display()))?;
+
+    if contents_str.trim().is_empty() {
+        return Ok(None);
+    }
+
+    let instance: JsonModel = serde_json::from_str(contents_str)
         .with_context(|| format!("File is not a valid JSON model: {}", path.display()))?;
 
     let mut snapshot = instance

tests/tests/serve.rs

@@ -186,3 +186,37 @@ fn move_folder_of_stuff() {
         );
     });
 }
+
+#[test]
+fn empty_json_model() {
+    run_serve_test("empty_json_model", |session, mut redactions| {
+        let info = session.get_api_rojo().unwrap();
+        let root_id = info.root_instance_id;
+
+        assert_yaml_snapshot!("empty_json_model_info", redactions.redacted_yaml(info));
+
+        let read_response = session.get_api_read(root_id).unwrap();
+        assert_yaml_snapshot!(
+            "empty_json_model_all",
+            read_response.intern_and_redact(&mut redactions, root_id)
+        );
+
+        fs::write(
+            session.path().join("src/test.model.json"),
+            r#"{"ClassName": "Model"}"#,
+        )
+        .unwrap();
+
+        let subscribe_response = session.get_api_subscribe(0).unwrap();
+        assert_yaml_snapshot!(
+            "empty_json_model_subscribe",
+            subscribe_response.intern_and_redact(&mut redactions, ())
+        );
+
+        let read_response = session.get_api_read(root_id).unwrap();
+        assert_yaml_snapshot!(
+            "empty_json_model_all-2",
+            read_response.intern_and_redact(&mut redactions, root_id)
+        );
+    });
+}