(MAINT) Restructure dsc-lib-jsonschema

This change refactors the `dsc-lib-jsonschema` library without modifying
any behavior.

This change:

- Splits the functions in the `transforms` module out into submodules
  and re-exports them from `transforms` - this keeps referencing the
  functions the way it was before but makes it easier to navigate the
  files, given their length.
- Makes the unit tests for `schema_utility_extensions` mirror the
  structure from the source code.
- Makes the integration tests for `transform` mirror the structure from
  the source code.

Author: michaeltlombardi

lib/dsc-lib-jsonschema/src/tests/mod.rs

@@ -13,5 +13,4 @@
 //! of the modules from the rest of the source tree.
 
 #[cfg(test)] mod schema_utility_extensions;
-#[cfg(test)] mod transforms;
 #[cfg(test)] mod vscode;

lib/dsc-lib-jsonschema/src/tests/schema_utility_extensions/mod.rs renamed to lib/dsc-lib-jsonschema/src/tests/schema_utility_extensions.rs

@@ -0,0 +1,218 @@
+use schemars::Schema;
+use serde_json::{Map, Value, json};
+
+use crate::vscode::VSCODE_KEYWORDS;
+
+/// Munges the generated schema for externally tagged enums into an idiomatic object schema.
+///
+/// Schemars generates the schema for externally tagged enums as a schema with the `oneOf`
+/// keyword where every tag is a different item in the array. Each item defines a type with a
+/// single property, requires that property, and disallows specifying any other properties.
+///
+/// This transformer returns the schema as a single object schema with each of the tags defined
+/// as properties. It sets both the `minProperties` and `maxProperties` keywords to `1`. This
+/// is more idiomatic, shorter to read and parse, easier to reason about, and matches the
+/// underlying data semantics more accurately.
+///
+/// This transformer should _only_ be used on externally tagged enums. You must specify it with the
+/// [schemars `transform()` attribute][`transform`].
+///
+/// # Examples
+///
+/// The following struct derives [`JsonSchema`] without specifying the [`transform`] attribute
+/// with [`idiomaticize_externally_tagged_enum`]:
+///
+/// ```
+/// use pretty_assertions::assert_eq;
+/// use serde_json;
+/// use schemars::{schema_for, JsonSchema, json_schema};
+/// #[derive(JsonSchema)]
+/// pub enum ExternallyTaggedEnum {
+///     Name(String),
+///     Count(f32),
+/// }
+///
+/// let generated_schema = schema_for!(ExternallyTaggedEnum);
+/// let expected_schema  = json_schema!({
+///     "$schema": "https://json-schema.org/draft/2020-12/schema",
+///     "title": "ExternallyTaggedEnum",
+///     "oneOf": [
+///         {
+///             "type": "object",
+///             "properties": {
+///                 "Name": {
+///                     "type": "string"
+///                 }
+///             },
+///             "additionalProperties": false,
+///             "required": ["Name"]
+///         },
+///         {
+///             "type": "object",
+///             "properties": {
+///                 "Count": {
+///                     "type": "number",
+///                     "format": "float"
+///                 }
+///             },
+///             "additionalProperties": false,
+///             "required": ["Count"]
+///         }
+///     ]
+/// });
+/// assert_eq!(generated_schema, expected_schema);
+/// ```
+///
+/// While the derived schema _does_ effectively validate the enum, it's difficult to understand
+/// without deep familiarity with JSON Schema. Compare it to the same enum with the
+/// [`idiomaticize_externally_tagged_enum`] transform applied:
+///
+/// ```
+/// use pretty_assertions::assert_eq;
+/// use serde_json;
+/// use schemars::{schema_for, JsonSchema, json_schema};
+/// use dsc_lib_jsonschema::transforms::idiomaticize_externally_tagged_enum;
+///
+/// #[derive(JsonSchema)]
+/// #[schemars(transform = idiomaticize_externally_tagged_enum)]
+/// pub enum ExternallyTaggedEnum {
+///     Name(String),
+///     Count(f32),
+/// }
+///
+/// let generated_schema = schema_for!(ExternallyTaggedEnum);
+/// let expected_schema  = json_schema!({
+///     "$schema": "https://json-schema.org/draft/2020-12/schema",
+///     "title": "ExternallyTaggedEnum",
+///     "type": "object",
+///     "properties": {
+///         "Name": {
+///             "type": "string"
+///         },
+///         "Count": {
+///             "type": "number",
+///             "format": "float"
+///         }
+///     },
+///     "minProperties": 1,
+///     "maxProperties": 1,
+///     "additionalProperties": false
+/// });
+/// assert_eq!(generated_schema, expected_schema);
+/// ```
+///
+/// The transformed schema is shorter, clearer, and idiomatic for JSON Schema draft 2019-09 and
+/// later. It validates values as effectively as the default output for an externally tagged
+/// enum, but is easier for your users and integrating developers to understand and work
+/// with.
+///
+/// # Panics
+///
+/// This transform panics when called against a generated schema that doesn't define the `oneOf`
+/// keyword. Schemars uses the `oneOf` keyword when generating subschemas for externally tagged
+/// enums. This transform panics on an invalid application of the transform to prevent unexpected
+/// behavior for the schema transformation. This ensures invalid applications are caught during
+/// development and CI instead of shipping broken schemas.
+///
+/// [`JsonSchema`]: schemars::JsonSchema
+/// [`transform`]: derive@schemars::JsonSchema
+pub fn idiomaticize_externally_tagged_enum(schema: &mut Schema) {
+    // First, retrieve the oneOf keyword entries. If this transformer was called against an invalid
+    // schema or subschema, it should fail fast.
+    let one_ofs = schema.get("oneOf")
+        .unwrap_or_else(|| panic_t!(
+            "transforms.idiomaticize_externally_tagged_enum.applies_to",
+            transforming_schema = serde_json::to_string_pretty(schema).unwrap()
+        ))
+        .as_array()
+        .unwrap_or_else(|| panic_t!(
+            "transforms.idiomaticize_externally_tagged_enum.oneOf_array",
+            transforming_schema = serde_json::to_string_pretty(schema).unwrap()
+        ));
+    // Initialize the map of properties to fill in when introspecting on the items in the oneOf array.
+    let mut properties_map = Map::new();
+
+    for item in one_ofs {
+        let item_data: Map<String, Value> = item.as_object()
+            .unwrap_or_else(|| panic_t!(
+                "transforms.idiomaticize_externally_tagged_enum.oneOf_item_as_object",
+                transforming_schema = serde_json::to_string_pretty(schema).unwrap(),
+                invalid_item = serde_json::to_string_pretty(item).unwrap()
+            ))
+            .clone();
+        // If we're accidentally operating on an invalid schema, short-circuit.
+        let item_data_type = item_data.get("type")
+            .unwrap_or_else(|| panic_t!(
+                "transforms.idiomaticize_externally_tagged_enum.oneOf_item_define_type",
+                transforming_schema = serde_json::to_string_pretty(schema).unwrap(),
+                invalid_item = serde_json::to_string_pretty(&item_data).unwrap()
+            ))
+            .as_str()
+            .unwrap_or_else(|| panic_t!(
+                "transforms.idiomaticize_externally_tagged_enum.oneOf_item_type_string",
+                transforming_schema = serde_json::to_string_pretty(schema).unwrap(),
+                invalid_item = serde_json::to_string_pretty(&item_data).unwrap()
+            ));
+        assert_t!(
+            !item_data_type.ne("object"),
+            "transforms.idiomaticize_externally_tagged_enum.oneOf_item_not_object_type",
+            transforming_schema = serde_json::to_string_pretty(schema).unwrap(),
+            invalid_item = serde_json::to_string_pretty(&item_data).unwrap(),
+            invalid_type = item_data_type
+        );
+        // Retrieve the title and description from the top-level of the item, if any. Depending on
+        // the implementation, these values might be set on the item, in the property, or both.
+        let item_title = item_data.get("title");
+        let item_desc = item_data.get("description");
+        // Retrieve the property definitions. There should never be more than one property per item,
+        // but this implementation doesn't guard against that edge case..
+        let properties_data = item_data.get("properties")
+            .unwrap_or_else(|| panic_t!(
+                "transforms.idiomaticize_externally_tagged_enum.oneOf_item_properties_missing",
+                transforming_schema = serde_json::to_string_pretty(schema).unwrap(),
+                invalid_item = serde_json::to_string_pretty(&item_data).unwrap(),
+            ))
+            .as_object()
+            .unwrap_or_else(|| panic_t!(
+                "transforms.idiomaticize_externally_tagged_enum.oneOf_item_properties_not_object",
+                transforming_schema = serde_json::to_string_pretty(schema).unwrap(),
+                invalid_item = serde_json::to_string_pretty(&item_data).unwrap(),
+            ))
+            .clone();
+        for property_name in properties_data.keys() {
+            // Retrieve the property definition to munge as needed.
+            let mut property_data = properties_data.get(property_name)
+                .unwrap() // can't fail because we're iterating on keys in the map
+                .as_object()
+                .unwrap_or_else(|| panic_t!(
+                    "transforms.idiomaticize_externally_tagged_enum.oneOf_item_properties_entry_not_object",
+                    transforming_schema = serde_json::to_string_pretty(schema).unwrap(),
+                    invalid_item = serde_json::to_string_pretty(&item_data).unwrap(),
+                    name = property_name
+                ))
+                .clone();
+            // Process the annotation keywords. If they are defined on the item but not the property,
+            // insert the item-defined keywords into the property data.
+            if let Some(t) = item_title && property_data.get("title").is_none() {
+                    property_data.insert("title".into(), t.clone());
+            }
+            if let Some(d) = item_desc && property_data.get("description").is_none() {
+                property_data.insert("description".into(), d.clone());
+            }
+            for keyword in VSCODE_KEYWORDS {
+                if let Some(keyword_value) = item_data.get(keyword) && property_data.get(keyword).is_none() {
+                    property_data.insert(keyword.to_string(), keyword_value.clone());
+                }
+            }
+            // Insert the processed property into the top-level properties definition.
+            properties_map.insert(property_name.into(), serde_json::Value::Object(property_data));
+        }
+    }
+    // Replace the oneOf array with an idiomatic object schema definition
+    schema.remove("oneOf");
+    schema.insert("type".to_string(), json!("object"));
+    schema.insert("minProperties".to_string(), json!(1));
+    schema.insert("maxProperties".to_string(), json!(1));
+    schema.insert("additionalProperties".to_string(), json!(false));
+    schema.insert("properties".to_string(), properties_map.into());
+}