Adding support for Throwable error result types in Kotlin (#741)

* Adding support for returning opaques as the error type of a result, as a custom Kotlin exception type * adding same support for throwable structs * clippy * fixing multiple inheritance * moooore clippy * test fix * new error log * making custom `error` attribute * clippy --------- Co-authored-by: Ellen Arteca <[email protected]>
rust-diplomat · Dec 9, 2024 · baa148b · baa148b
1 parent 8593fda
commit baa148b
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Showing 26 changed files with 128 additions and 33 deletions.
diff --git a/core/src/hir/attrs.rs b/core/src/hir/attrs.rs
@@ -41,6 +41,8 @@ pub struct Attrs {
     /// This attribute does not participate in inheritance and must always
     /// be specified on individual methods
     pub special_method: Option<SpecialMethod>,
+    /// This user-defined type can be used as the error type in a Result.
+    pub custom_errors: bool,
 
     /// From #[diplomat::demo()]. Created from [`crate::ast::attrs::Attrs::demo_attrs`].
     /// List of attributes specific to automatic demo generation.
@@ -349,9 +351,16 @@ impl Attrs {
                                 continue;
                             }
                         }
+                    } else if path == "error" {
+                        if !support.custom_errors {
+                            maybe_error_unsupported(auto_found, "error", backend, errors);
+                            continue;
+                        }
+                        auto_used = true;
+                        this.custom_errors = true;
                     } else {
                         errors.push(LoweringError::Other(format!(
-                            "Unknown diplomat attribute {path}: expected one of: `disable, rename, namespace, constructor, stringifier, comparison, named_constructor, getter, setter, indexer`"
+                            "Unknown diplomat attribute {path}: expected one of: `disable, rename, namespace, constructor, stringifier, comparison, named_constructor, getter, setter, indexer, error`"
                         )));
                     }
                     if auto_found && !auto_used {
@@ -361,7 +370,7 @@ impl Attrs {
                     }
                 } else {
                     errors.push(LoweringError::Other(format!(
-                        "Unknown diplomat attribute {path:?}: expected one of: `disable, rename, namespace, constructor, stringifier, comparison, named_constructor, getter, setter, indexer`"
+                        "Unknown diplomat attribute {path:?}: expected one of: `disable, rename, namespace, constructor, stringifier, comparison, named_constructor, getter, setter, indexer, error`"
                     )));
                 }
             }
@@ -458,6 +467,7 @@ impl Attrs {
             rename,
             abi_rename,
             special_method,
+            custom_errors,
             demo_attrs: _,
         } = &self;
 
@@ -745,6 +755,17 @@ impl Attrs {
                 )));
             }
         }
+
+        if *custom_errors
+            && !matches!(
+                context,
+                AttributeContext::Type(..) | AttributeContext::Trait(..)
+            )
+        {
+            errors.push(LoweringError::Other(
+                "`error` can only be used on types".to_string(),
+            ));
+        }
     }
 
     pub(crate) fn for_inheritance(&self, context: AttrInheritContext) -> Attrs {
@@ -773,6 +794,8 @@ impl Attrs {
             abi_rename: Default::default(),
             // Never inherited
             special_method: None,
+            // Not inherited
+            custom_errors: false,
             demo_attrs: Default::default(),
         }
     }
@@ -849,6 +872,8 @@ pub struct BackendAttrSupport {
     pub callbacks: bool,
     /// Allowing traits
     pub traits: bool,
+    /// Marking a user-defined type as being a valid error result type.
+    pub custom_errors: bool,
 }
 
 impl BackendAttrSupport {
@@ -875,6 +900,7 @@ impl BackendAttrSupport {
             option: true,
             callbacks: true,
             traits: true,
+            custom_errors: true,
         }
     }
 }
@@ -1007,6 +1033,7 @@ impl AttributeValidator for BasicAttributeValidator {
                 option,
                 callbacks,
                 traits,
+                custom_errors,
             } = self.support;
             match value {
                 "namespacing" => namespacing,
@@ -1029,6 +1056,7 @@ impl AttributeValidator for BasicAttributeValidator {
                 "option" => option,
                 "callbacks" => callbacks,
                 "traits" => traits,
+                "custom_errors" => custom_errors,
                 _ => {
                     return Err(LoweringError::Other(format!(
                         "Unknown supports = value found: {value}"

diff --git a/core/src/hir/snapshots/diplomat_core__hir__elision__tests__elision_in_struct.snap b/core/src/hir/snapshots/diplomat_core__hir__elision__tests__elision_in_struct.snap
@@ -1,5 +1,6 @@
 ---
 source: core/src/hir/elision.rs
+assertion_line: 536
 expression: method
 ---
 Method {
@@ -44,6 +45,7 @@ Method {
                     pattern: None,
                 },
                 special_method: None,
+                custom_errors: false,
                 demo_attrs: DemoInfo {
                     generate: false,
                     default_constructor: false,
@@ -97,6 +99,7 @@ Method {
                     pattern: None,
                 },
                 special_method: None,
+                custom_errors: false,
                 demo_attrs: DemoInfo {
                     generate: false,
                     default_constructor: false,
@@ -123,6 +126,7 @@ Method {
             pattern: None,
         },
         special_method: None,
+        custom_errors: false,
         demo_attrs: DemoInfo {
             generate: false,
             default_constructor: false,

diff --git a/core/src/hir/snapshots/diplomat_core__hir__elision__tests__simple_mod.snap b/core/src/hir/snapshots/diplomat_core__hir__elision__tests__simple_mod.snap
@@ -1,5 +1,6 @@
 ---
 source: core/src/hir/elision.rs
+assertion_line: 473
 expression: tcx
 ---
 TypeContext {
@@ -47,6 +48,7 @@ TypeContext {
                             pattern: None,
                         },
                         special_method: None,
+                        custom_errors: false,
                         demo_attrs: DemoInfo {
                             generate: false,
                             default_constructor: false,
@@ -104,6 +106,7 @@ TypeContext {
                                     pattern: None,
                                 },
                                 special_method: None,
+                                custom_errors: false,
                                 demo_attrs: DemoInfo {
                                     generate: false,
                                     default_constructor: false,
@@ -149,6 +152,7 @@ TypeContext {
                             pattern: None,
                         },
                         special_method: None,
+                        custom_errors: false,
                         demo_attrs: DemoInfo {
                             generate: false,
                             default_constructor: false,
@@ -172,6 +176,7 @@ TypeContext {
                     pattern: None,
                 },
                 special_method: None,
+                custom_errors: false,
                 demo_attrs: DemoInfo {
                     generate: false,
                     default_constructor: false,
@@ -236,6 +241,7 @@ TypeContext {
                             pattern: None,
                         },
                         special_method: None,
+                        custom_errors: false,
                         demo_attrs: DemoInfo {
                             generate: false,
                             default_constructor: false,
@@ -295,6 +301,7 @@ TypeContext {
                                     pattern: None,
                                 },
                                 special_method: None,
+                                custom_errors: false,
                                 demo_attrs: DemoInfo {
                                     generate: false,
                                     default_constructor: false,
@@ -333,6 +340,7 @@ TypeContext {
                                     pattern: None,
                                 },
                                 special_method: None,
+                                custom_errors: false,
                                 demo_attrs: DemoInfo {
                                     generate: false,
                                     default_constructor: false,
@@ -372,6 +380,7 @@ TypeContext {
                             pattern: None,
                         },
                         special_method: None,
+                        custom_errors: false,
                         demo_attrs: DemoInfo {
                             generate: false,
                             default_constructor: false,
@@ -395,6 +404,7 @@ TypeContext {
                     pattern: None,
                 },
                 special_method: None,
+                custom_errors: false,
                 demo_attrs: DemoInfo {
                     generate: false,
                     default_constructor: false,
@@ -441,6 +451,7 @@ TypeContext {
                     pattern: None,
                 },
                 special_method: None,
+                custom_errors: false,
                 demo_attrs: DemoInfo {
                     generate: false,
                     default_constructor: false,

diff --git a/example/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/DataProvider.kt b/example/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/DataProvider.kt
@@ -52,7 +52,7 @@ class DataProvider internal constructor (
             if (returnVal.isOk == 1.toByte()) {
                 return Unit.ok()
             } else {
-                return Unit.err()
+                return Unit.primitive_err()
             }
         }
     }

diff --git a/example/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/FixedDecimal.kt b/example/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/FixedDecimal.kt
@@ -66,7 +66,7 @@ class FixedDecimal internal constructor (
             val returnString = DW.writeToString(write)
             return returnString.ok()
         } else {
-            return Unit.err()
+            return Unit.primitive_err()
         }
     }
 

diff --git a/example/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/FixedDecimalFormatter.kt b/example/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/FixedDecimalFormatter.kt
@@ -46,7 +46,7 @@ class FixedDecimalFormatter internal constructor (
                 CLEANER.register(returnOpaque, FixedDecimalFormatter.FixedDecimalFormatterCleaner(handle, FixedDecimalFormatter.lib));
                 return returnOpaque.ok()
             } else {
-                return Unit.err()
+                return Unit.primitive_err()
             }
         }
     }

diff --git a/example/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/Lib.kt b/example/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/Lib.kt
@@ -331,10 +331,14 @@ internal fun <T> T.ok(): Result<T> {
     return Result.success(this)
 }
 
-internal fun <T, E> E.err(): Result<T> {
+internal fun <T, E> E.primitive_err(): Result<T> {
     return Result.failure(RuntimeException("Received error $this"))
 }
 
+internal fun <T> Throwable.err(): Result<T> {
+    return Result.failure(this)
+}
+
 internal class ResultPointerUnitUnion: Union() {
     @JvmField
     internal var ok: Pointer = Pointer(0)

diff --git a/feature_tests/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/ErrorStruct.kt b/feature_tests/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/ErrorStruct.kt
diff --git a/feature_tests/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/Lib.kt b/feature_tests/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/Lib.kt
diff --git a/feature_tests/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/MyZst.kt b/feature_tests/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/MyZst.kt
diff --git a/feature_tests/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/OptionString.kt b/feature_tests/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/OptionString.kt
diff --git a/feature_tests/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/ResultOpaque.kt b/feature_tests/kotlin/somelib/src/main/kotlin/dev/diplomattest/somelib/ResultOpaque.kt
diff --git a/feature_tests/kotlin/somelib/src/test/kotlin/dev/diplomattest/somelib/ResultOpaqueTest.kt b/feature_tests/kotlin/somelib/src/test/kotlin/dev/diplomattest/somelib/ResultOpaqueTest.kt