Allow to define custom expectation message for type with #[serde(expecting = "...")]

Closes #1883
2026-04-22 16:08:05 +00:00 · 2020-10-23 00:54:13 +05:00
parent 23c14e5f33
commit 104ad9a7dd
6 changed files with 287 additions and 5 deletions
@@ -2633,3 +2633,200 @@ fn test_flatten_any_after_flatten_struct() {
        ],
    );
 }
+
+/// https://github.com/serde-rs/serde/issues/1883
+#[test]
+fn test_expecting_message() {
+    #[derive(Deserialize, PartialEq, Debug)]
+    #[serde(expecting = "something strange...")]
+    struct Unit;
+
+    #[derive(Deserialize)]
+    #[serde(expecting = "something strange...")]
+    struct Newtype(bool);
+
+    #[derive(Deserialize)]
+    #[serde(expecting = "something strange...")]
+    struct Tuple(u32, bool);
+
+    #[derive(Deserialize)]
+    #[serde(expecting = "something strange...")]
+    struct Struct {
+        question: String,
+        answer: u32,
+    }
+
+    assert_de_tokens_error::<Unit>(
+        &[Token::Str("Unit")],
+        r#"invalid type: string "Unit", expected something strange..."#
+    );
+
+    assert_de_tokens_error::<Newtype>(
+        &[Token::Str("Newtype")],
+        r#"invalid type: string "Newtype", expected something strange..."#
+    );
+
+    assert_de_tokens_error::<Tuple>(
+        &[Token::Str("Tuple")],
+        r#"invalid type: string "Tuple", expected something strange..."#
+    );
+
+    assert_de_tokens_error::<Struct>(
+        &[Token::Str("Struct")],
+        r#"invalid type: string "Struct", expected something strange..."#
+    );
+}
+
+#[test]
+fn test_expecting_message_externally_tagged_enum() {
+    #[derive(Deserialize)]
+    #[serde(expecting = "something strange...")]
+    enum Enum {
+        ExternallyTagged,
+    }
+
+    assert_de_tokens_error::<Enum>(
+        &[
+            Token::Str("ExternallyTagged"),
+        ],
+        r#"invalid type: string "ExternallyTagged", expected something strange..."#
+    );
+
+    // Check that #[serde(expecting = "...")] doesn't affect variant identifier error message
+    assert_de_tokens_error::<Enum>(
+        &[
+            Token::Enum { name: "Enum" },
+            Token::Unit,
+        ],
+        r#"invalid type: unit value, expected variant identifier"#
+    );
+}
+
+#[test]
+fn test_expecting_message_internally_tagged_enum() {
+    #[derive(Deserialize)]
+    #[serde(tag = "tag")]
+    #[serde(expecting = "something strange...")]
+    enum Enum {
+        InternallyTagged,
+    }
+
+    assert_de_tokens_error::<Enum>(
+        &[
+            Token::Str("InternallyTagged"),
+        ],
+        r#"invalid type: string "InternallyTagged", expected something strange..."#
+    );
+
+    // Check that #[serde(expecting = "...")] doesn't affect variant identifier error message
+    assert_de_tokens_error::<Enum>(
+        &[
+            Token::Map { len: None },
+            Token::Str("tag"),
+            Token::Unit,
+        ],
+        r#"invalid type: unit value, expected variant identifier"#
+    );
+}
+
+#[test]
+fn test_expecting_message_adjacently_tagged_enum() {
+    #[derive(Deserialize)]
+    #[serde(tag = "tag", content = "content")]
+    #[serde(expecting = "something strange...")]
+    enum Enum {
+        AdjacentlyTagged,
+    }
+
+    assert_de_tokens_error::<Enum>(
+        &[
+            Token::Str("AdjacentlyTagged"),
+        ],
+        r#"invalid type: string "AdjacentlyTagged", expected something strange..."#
+    );
+
+    assert_de_tokens_error::<Enum>(
+        &[
+            Token::Map { len: None },
+            Token::Unit,
+        ],
+        r#"invalid type: unit value, expected "tag", "content", or other ignored fields"#
+    );
+
+    // Check that #[serde(expecting = "...")] doesn't affect variant identifier error message
+    assert_de_tokens_error::<Enum>(
+        &[
+            Token::Map { len: None },
+            Token::Str("tag"),
+            Token::Unit,
+        ],
+        r#"invalid type: unit value, expected variant identifier"#
+    );
+}
+
+#[test]
+fn test_expecting_message_untagged_tagged_enum() {
+    #[derive(Deserialize)]
+    #[serde(untagged)]
+    #[serde(expecting = "something strange...")]
+    enum Enum {
+        Untagged,
+    }
+
+    assert_de_tokens_error::<Enum>(
+        &[
+            Token::Str("Untagged"),
+        ],
+        r#"something strange..."#
+    );
+}
+
+#[test]
+fn test_expecting_message_identifier_enum() {
+    #[derive(Deserialize)]
+    #[serde(field_identifier)]
+    #[serde(expecting = "something strange...")]
+    enum FieldEnum {
+        Field,
+    }
+
+    #[derive(Deserialize)]
+    #[serde(variant_identifier)]
+    #[serde(expecting = "something strange...")]
+    enum VariantEnum {
+        Variant,
+    }
+
+    assert_de_tokens_error::<FieldEnum>(
+        &[
+            Token::Unit,
+        ],
+        r#"invalid type: unit value, expected something strange..."#
+    );
+
+    assert_de_tokens_error::<FieldEnum>(
+        &[
+            Token::Enum { name: "FieldEnum" },
+            Token::Str("Unknown"),
+            Token::None,
+        ],
+        r#"invalid type: map, expected something strange..."#
+    );
+
+
+    assert_de_tokens_error::<VariantEnum>(
+        &[
+            Token::Unit,
+        ],
+        r#"invalid type: unit value, expected something strange..."#
+    );
+
+    assert_de_tokens_error::<VariantEnum>(
+        &[
+            Token::Enum { name: "VariantEnum" },
+            Token::Str("Unknown"),
+            Token::None,
+        ],
+        r#"invalid type: map, expected something strange..."#
+    );
+}