feat(errors): improve message generation for schema validation failures

src/index.js

@@ -41,7 +41,7 @@ const getErrorMessage = (outputUnit, schema, instance) => {
   }
 
   if (outputUnit.keyword === "https://json-schema.org/keyword/maxLength") {
-    return `The instance should be atmost ${Schema.value(schema)} characters long.`;
+    return `The instance should be at most ${Schema.value(schema)} characters long.`;
   }
 
   if (outputUnit.keyword === "https://json-schema.org/keyword/type") {
@@ -118,5 +118,25 @@ const getErrorMessage = (outputUnit, schema, instance) => {
 
     return `Unexpected value "${currentValue}". Expected one of: ${allowedValues.join(",")}.`;
   }
+
+  if (outputUnit.keyword === "https://json-schema.org/keyword/pattern") {
+    return `The instance should match the pattern: ${Schema.value(schema)}.`;
+  }
+
+  if (outputUnit.keyword === "https://json-schema.org/keyword/minItems") {
+    return `The instance should have at least ${Schema.value(schema)} items.`;
+  }
+
+  if (outputUnit.keyword === "https://json-schema.org/keyword/maxItems") {
+    return `The instance should have at most ${Schema.value(schema)} items.`;
+  }
+
+  if (outputUnit.keyword === "https://json-schema.org/keyword/uniqueItems") {
+    return `The array should not contain duplicate items.`;
+  }
+
+  if (outputUnit.keyword === "https://json-schema.org/keyword/format") {
+    return `The instance should match the format: ${Schema.value(schema)}.`;
+  }
   throw Error("TODO: Error message not implemented");
 };

src/keywordErrorMessage.test.js

@@ -65,7 +65,7 @@ describe("Error messages", () => {
     expect(result.errors).to.eql([{
       schemaLocation: "https://example.com/main#/maxLength",
       instanceLocation: "#",
-      message: "The instance should be atmost 3 characters long."
+      message: "The instance should be at most 3 characters long."
     }
     ]);
   });
@@ -382,4 +382,141 @@ describe("Error messages", () => {
       message: `Unexpected value "rwd".  Did you mean "red"?`
     }]);
   });
+  test("pattern", async () => {
+    registerSchema({
+      $schema: "https://json-schema.org/draft/2020-12/schema",
+      pattern: "^[a-z]+$"
+    }, schemaUri);
+
+    const instance = "ABC123";
+    const output = {
+      valid: false,
+      errors: [
+        {
+          absoluteKeywordLocation: "https://example.com/main#/pattern",
+          instanceLocation: "#"
+        }
+      ]
+    };
+
+    const result = await betterJsonSchemaErrors(instance, output, schemaUri);
+    expect(result.errors).to.eql([
+      {
+        schemaLocation: "https://example.com/main#/pattern",
+        instanceLocation: "#",
+        message: "The instance should match the pattern: ^[a-z]+$."
+      }
+    ]);
+  });
+
+  test("minItems", async () => {
+    registerSchema({
+      $schema: "https://json-schema.org/draft/2020-12/schema",
+      type: "array",
+      minItems: 3
+    }, schemaUri);
+
+    const instance = [1];
+    const output = {
+      valid: false,
+      errors: [
+        {
+          absoluteKeywordLocation: "https://example.com/main#/minItems",
+          instanceLocation: "#"
+        }
+      ]
+    };
+
+    const result = await betterJsonSchemaErrors(instance, output, schemaUri);
+    expect(result.errors).to.eql([
+      {
+        schemaLocation: "https://example.com/main#/minItems",
+        instanceLocation: "#",
+        message: "The instance should have at least 3 items."
+      }
+    ]);
+  });
+
+  test("maxItems", async () => {
+    registerSchema({
+      $schema: "https://json-schema.org/draft/2020-12/schema",
+      type: "array",
+      maxItems: 2
+    }, schemaUri);
+
+    const instance = [1, 2, 3];
+    const output = {
+      valid: false,
+      errors: [
+        {
+          absoluteKeywordLocation: "https://example.com/main#/maxItems",
+          instanceLocation: "#"
+        }
+      ]
+    };
+
+    const result = await betterJsonSchemaErrors(instance, output, schemaUri);
+    expect(result.errors).to.eql([
+      {
+        schemaLocation: "https://example.com/main#/maxItems",
+        instanceLocation: "#",
+        message: "The instance should have at most 2 items."
+      }
+    ]);
+  });
+
+  test("uniqueItems", async () => {
+    registerSchema({
+      $schema: "https://json-schema.org/draft/2020-12/schema",
+      type: "array",
+      uniqueItems: true
+    }, schemaUri);
+
+    const instance = [1, 1];
+    const output = {
+      valid: false,
+      errors: [
+        {
+          absoluteKeywordLocation: "https://example.com/main#/uniqueItems",
+          instanceLocation: "#"
+        }
+      ]
+    };
+
+    const result = await betterJsonSchemaErrors(instance, output, schemaUri);
+    expect(result.errors).to.eql([
+      {
+        schemaLocation: "https://example.com/main#/uniqueItems",
+        instanceLocation: "#",
+        message: "The array should not contain duplicate items."
+      }
+    ]);
+  });
+
+  test("format: email", async () => {
+    registerSchema({
+      $schema: "https://json-schema.org/draft/2020-12/schema",
+      format: "email"
+    }, schemaUri);
+
+    const instance = "not-an-email";
+    const output = {
+      valid: false,
+      errors: [
+        {
+          absoluteKeywordLocation: "https://example.com/main#/format",
+          instanceLocation: "#"
+        }
+      ]
+    };
+
+    const result = await betterJsonSchemaErrors(instance, output, schemaUri);
+    expect(result.errors).to.eql([
+      {
+        schemaLocation: "https://example.com/main#/format",
+        instanceLocation: "#",
+        message: "The instance should match the format: email."
+      }
+    ]);
+  });
 });

src/normalizeOutputFormat/normalizeOutput.test.js

@@ -284,7 +284,7 @@ describe("Error Output Normalization", () => {
     ]);
   });
 
-  test("when error output doesnot contain any of these three keyword (valid, absoluteKeywordLocation, instanceLocation)", async () => {
+  test("when error output does not contain any of these three keyword (valid, absoluteKeywordLocation, instanceLocation)", async () => {
     registerSchema({
       $schema: "https://json-schema.org/draft/2020-12/schema",
       items: { $ref: "#/$defs/foo" },
@@ -391,4 +391,136 @@ describe("Error Output Normalization", () => {
       }
     ]);
   });
+
+  test("should return a pattern error message", async () => {
+    registerSchema({
+      $schema: "https://json-schema.org/draft/2020-12/schema",
+      pattern: "^[a-z]+$"
+    }, schemaUri);
+
+    const instance = "ABC123";
+
+    const output = {
+      valid: false,
+      errors: [
+        {
+          absoluteKeywordLocation: "https://example.com/main#/pattern",
+          instanceLocation: "#"
+        }
+      ]
+    };
+
+    const result = await betterJsonSchemaErrors(instance, output, schemaUri);
+    expect(result.errors).to.eql([{
+      schemaLocation: "https://example.com/main#/pattern",
+      instanceLocation: "#",
+      message: "The instance should match the pattern: ^[a-z]+$."
+    }]);
+  });
+
+  test("should return a minItems error message", async () => {
+    registerSchema({
+      $schema: "https://json-schema.org/draft/2020-12/schema",
+      type: "array",
+      minItems: 3
+    }, schemaUri);
+
+    const instance = [1];
+
+    const output = {
+      valid: false,
+      errors: [
+        {
+          absoluteKeywordLocation: "https://example.com/main#/minItems",
+          instanceLocation: "#"
+        }
+      ]
+    };
+
+    const result = await betterJsonSchemaErrors(instance, output, schemaUri);
+    expect(result.errors).to.eql([{
+      schemaLocation: "https://example.com/main#/minItems",
+      instanceLocation: "#",
+      message: "The instance should have at least 3 items."
+    }]);
+  });
+
+  test("should return a maxItems error message", async () => {
+    registerSchema({
+      $schema: "https://json-schema.org/draft/2020-12/schema",
+      type: "array",
+      maxItems: 2
+    }, schemaUri);
+
+    const instance = [1, 2, 3];
+
+    const output = {
+      valid: false,
+      errors: [
+        {
+          absoluteKeywordLocation: "https://example.com/main#/maxItems",
+          instanceLocation: "#"
+        }
+      ]
+    };
+
+    const result = await betterJsonSchemaErrors(instance, output, schemaUri);
+    expect(result.errors).to.eql([{
+      schemaLocation: "https://example.com/main#/maxItems",
+      instanceLocation: "#",
+      message: "The instance should have at most 2 items."
+    }]);
+  });
+
+  test("should return a uniqueItems error message", async () => {
+    registerSchema({
+      $schema: "https://json-schema.org/draft/2020-12/schema",
+      type: "array",
+      uniqueItems: true
+    }, schemaUri);
+
+    const instance = [1, 1];
+    const output = {
+      valid: false,
+      errors: [
+        {
+          absoluteKeywordLocation: "https://example.com/main#/uniqueItems",
+          instanceLocation: "#"
+        }
+      ]
+    };
+
+    const result = await betterJsonSchemaErrors(instance, output, schemaUri);
+    expect(result.errors).to.eql([{
+      schemaLocation: "https://example.com/main#/uniqueItems",
+      instanceLocation: "#",
+      message: "The array should not contain duplicate items."
+    }]);
+  });
+
+  test("should return a format error message for email", async () => {
+    registerSchema({
+      $schema: "https://json-schema.org/draft/2020-12/schema",
+      format: "email"
+    }, schemaUri);
+
+    const instance = "not-an-email";
+
+    const output = {
+      valid: false,
+      errors: [
+        {
+          absoluteKeywordLocation: "https://example.com/main#/format",
+          instanceLocation: "#"
+        }
+      ]
+    };
+
+    const result = await betterJsonSchemaErrors(instance, output, schemaUri);
+    expect(result.errors).to.eql([{
+      schemaLocation: "https://example.com/main#/format",
+      instanceLocation: "#",
+      message: "The instance should match the format: email."
+    }]);
+  });
 });