Wrapper JSON Overhaul (#224)

Wrapper JSON Overhaul

Wrapper newtypes will generate custom implementations that will defer to
the inner type's JSON traits instead of deriving to get them.
This gives us much nicer JSON implementations allowing directly `T`
instead of `{ inner: T }`.

Bytes newtypes will have a specialization that serializes to hex
bytestring instead of the `[number]` array that would otherwise be used.

Introduces `@custom_json` comment DSL for newtypes that tell
cddl-codegen to avoid generating/deriving any JSON traits under the
assumption that some custom trait impls will be provided post-generation
by the user.

.gitignore

@@ -16,3 +16,4 @@ book/
 # Test files
 tests/*/export/**
 tests/*/export_wasm/**
+tests/*/export_preserve/**

docs/docs/comment_dsl.mdx

@@ -96,6 +96,14 @@ Putting this comment on a type forces that type to derive those traits even if i
 This is useful for when you are writing utility code that would put them in a map and want the generated code to have it already,
 which is particularly useful for re-generating as it lets your `mod.rs` files remain untouched.
 
+## @custom_json
+
+```cddl
+foo = uint ; @newtype @custom_json
+```
+
+Avoids generating and/or deriving json-related traits under the assumption that the user will supply their own implementation to be used in the generated library.
+
 ## _CDDL_CODEGEN_EXTERN_TYPE_
 
 While not as a comment, this allows you to compose in hand-written structs into a cddl spec.

src/comment_ast.rs

@@ -12,6 +12,7 @@ pub struct RuleMetadata {
     pub is_newtype: bool,
     pub no_alias: bool,
     pub used_as_key: bool,
+    pub custom_json: bool,
 }
 
 pub fn merge_metadata(r1: &RuleMetadata, r2: &RuleMetadata) -> RuleMetadata {
@@ -26,6 +27,7 @@ pub fn merge_metadata(r1: &RuleMetadata, r2: &RuleMetadata) -> RuleMetadata {
         is_newtype: r1.is_newtype || r2.is_newtype,
         no_alias: r1.no_alias || r2.no_alias,
         used_as_key: r1.used_as_key || r2.used_as_key,
+        custom_json: r1.custom_json || r2.custom_json,
     };
     merged.verify();
     merged
@@ -36,6 +38,7 @@ enum ParseResult {
     Name(String),
     DontGenAlias,
     UsedAsKey,
+    CustomJson,
 }
 
 impl RuleMetadata {
@@ -61,6 +64,9 @@ impl RuleMetadata {
                 ParseResult::UsedAsKey => {
                     base.used_as_key = true;
                 }
+                ParseResult::CustomJson => {
+                    base.custom_json = true;
+                }
             }
         }
         base.verify();
@@ -101,9 +107,21 @@ fn tag_used_as_key(input: &str) -> IResult<&str, ParseResult> {
     Ok((input, ParseResult::UsedAsKey))
 }
 
+fn tag_custom_json(input: &str) -> IResult<&str, ParseResult> {
+    let (input, _) = tag("@custom_json")(input)?;
+
+    Ok((input, ParseResult::CustomJson))
+}
+
 fn whitespace_then_tag(input: &str) -> IResult<&str, ParseResult> {
     let (input, _) = take_while(char::is_whitespace)(input)?;
-    let (input, result) = alt((tag_name, tag_newtype, tag_no_alias, tag_used_as_key))(input)?;
+    let (input, result) = alt((
+        tag_name,
+        tag_newtype,
+        tag_no_alias,
+        tag_used_as_key,
+        tag_custom_json,
+    ))(input)?;
 
     Ok((input, result))
 }
@@ -144,6 +162,7 @@ fn parse_comment_name() {
                 is_newtype: false,
                 no_alias: false,
                 used_as_key: false,
+                custom_json: false,
             }
         ))
     );
@@ -160,6 +179,7 @@ fn parse_comment_newtype() {
                 is_newtype: true,
                 no_alias: false,
                 used_as_key: false,
+                custom_json: false,
             }
         ))
     );
@@ -176,6 +196,7 @@ fn parse_comment_newtype_and_name() {
                 is_newtype: true,
                 no_alias: false,
                 used_as_key: false,
+                custom_json: false,
             }
         ))
     );
@@ -192,6 +213,7 @@ fn parse_comment_newtype_and_name_and_used_as_key() {
                 is_newtype: true,
                 no_alias: false,
                 used_as_key: true,
+                custom_json: false,
             }
         ))
     );
@@ -208,6 +230,7 @@ fn parse_comment_used_as_key() {
                 is_newtype: false,
                 no_alias: false,
                 used_as_key: true,
+                custom_json: false,
             }
         ))
     );
@@ -224,6 +247,7 @@ fn parse_comment_newtype_and_name_inverse() {
                 is_newtype: true,
                 no_alias: false,
                 used_as_key: false,
+                custom_json: false,
             }
         ))
     );
@@ -240,6 +264,24 @@ fn parse_comment_name_noalias() {
                 is_newtype: false,
                 no_alias: true,
                 used_as_key: false,
+                custom_json: false,
+            }
+        ))
+    );
+}
+
+#[test]
+fn parse_comment_newtype_and_custom_json() {
+    assert_eq!(
+        rule_metadata("@custom_json @newtype"),
+        Ok((
+            "",
+            RuleMetadata {
+                name: None,
+                is_newtype: true,
+                no_alias: false,
+                used_as_key: false,
+                custom_json: true,
             }
         ))
     );