feat: enrich ParseError with schema and value context

Include the schema string and the input value in `ParseError` to
provide more helpful debugging information when parsing fails.

src/parser.ts

@@ -14,10 +14,20 @@ export class ParseError extends Error {
   constructor(
     message: string,
     public position?: number,
+    public schema?: string,
+    public value?: string,
   ) {
-    super(
-      position !== undefined ? `${message} at position ${position}` : message,
-    );
+    let fullMessage = message;
+    if (position !== undefined) {
+      fullMessage += ` at position ${position}`;
+    }
+    if (schema !== undefined) {
+      fullMessage += `. Schema: ${schema}`;
+    }
+    if (value !== undefined) {
+      fullMessage += `. Value: ${value}`;
+    }
+    super(fullMessage);
     this.name = "ParseError";
   }
 }

src/value-parser.ts

@@ -7,13 +7,16 @@ import type {
   UnionSchema,
 } from "./types";
 import { ParseError } from "./parser";
+import { schemaToTypeString } from "./type-utils";
 
 class ValueParser {
   private input: string;
+  private schemaString: string;
   private pos: number = 0;
 
-  constructor(input: string) {
+  constructor(input: string, schemaString: string) {
     this.input = input;
+    this.schemaString = schemaString;
   }
 
   private peek(): string {
@@ -71,6 +74,8 @@ class ValueParser {
         throw new ParseError(
           `Unknown schema type: ${(schema as { type: string }).type}`,
           this.pos,
+          this.schemaString,
+          this.input,
         );
     }
   }
@@ -109,7 +114,12 @@ class ValueParser {
     }
     const num = parseFloat(numStr);
     if (isNaN(num)) {
-      throw new ParseError("Invalid number", this.pos - numStr.length);
+      throw new ParseError(
+        "Invalid number",
+        this.pos - numStr.length,
+        this.schemaString,
+        this.input,
+      );
     }
     return num;
   }
@@ -121,10 +131,20 @@ class ValueParser {
     }
     const num = parseFloat(numStr);
     if (isNaN(num)) {
-      throw new ParseError("Invalid number", this.pos - numStr.length);
+      throw new ParseError(
+        "Invalid number",
+        this.pos - numStr.length,
+        this.schemaString,
+        this.input,
+      );
     }
     if (!Number.isInteger(num)) {
-      throw new ParseError("Expected integer value", this.pos - numStr.length);
+      throw new ParseError(
+        "Expected integer value",
+        this.pos - numStr.length,
+        this.schemaString,
+        this.input,
+      );
     }
     return num;
   }
@@ -140,7 +160,12 @@ class ValueParser {
     if (this.consumeStr("false")) {
       return false;
     }
-    throw new ParseError("Expected true or false", this.pos);
+    throw new ParseError(
+      "Expected true or false",
+      this.pos,
+      this.schemaString,
+      this.input,
+    );
   }
 
   private parseStringLiteralValue(schema: StringLiteralSchema): string {
@@ -174,6 +199,8 @@ class ValueParser {
             throw new ParseError(
               `Invalid value '"${value}"'. Expected '"${schema.value}"'`,
               this.pos,
+              this.schemaString,
+              this.input,
             );
           }
 
@@ -183,7 +210,12 @@ class ValueParser {
         }
       }
 
-      throw new ParseError("Unterminated string literal", this.pos);
+      throw new ParseError(
+        "Unterminated string literal",
+        this.pos,
+        this.schemaString,
+        this.input,
+      );
     } else {
       // 不带引号的字符串，像普通字符串一样解析
       let value = "";
@@ -201,6 +233,8 @@ class ValueParser {
         throw new ParseError(
           `Invalid value '${value}'. Expected '${schema.value}'`,
           this.pos - value.length,
+          this.schemaString,
+          this.input,
         );
       }
 
@@ -227,6 +261,8 @@ class ValueParser {
     throw new ParseError(
       `Value does not match any union member. Tried ${schema.members.length} alternatives.`,
       this.pos,
+      this.schemaString,
+      this.input,
     );
   }
 
@@ -240,7 +276,12 @@ class ValueParser {
       this.consume();
       hasOpenBracket = true;
     } else if (!allowOmitBrackets) {
-      throw new ParseError("Expected [", this.pos);
+      throw new ParseError(
+        "Expected [",
+        this.pos,
+        this.schemaString,
+        this.input,
+      );
     }
 
     this.skipWhitespace();
@@ -272,7 +313,12 @@ class ValueParser {
 
       if (i < schema.elements.length - 1) {
         if (!this.consumeStr(";")) {
-          throw new ParseError("Expected ;", this.pos);
+          throw new ParseError(
+            "Expected ;",
+            this.pos,
+            this.schemaString,
+            this.input,
+          );
         }
       }
     }
@@ -281,7 +327,12 @@ class ValueParser {
 
     if (hasOpenBracket) {
       if (!this.consumeStr("]")) {
-        throw new ParseError("Expected ]", this.pos);
+        throw new ParseError(
+          "Expected ]",
+          this.pos,
+          this.schemaString,
+          this.input,
+        );
       }
     }
 
@@ -325,7 +376,12 @@ class ValueParser {
     }
 
     if (!hasOpenBracket && !allowOmitBrackets && !elementIsTupleOrArray) {
-      throw new ParseError("Expected [", this.pos);
+      throw new ParseError(
+        "Expected [",
+        this.pos,
+        this.schemaString,
+        this.input,
+      );
     }
 
     this.skipWhitespace();
@@ -351,7 +407,12 @@ class ValueParser {
 
     if (hasOpenBracket) {
       if (!this.consumeStr("]")) {
-        throw new ParseError("Expected ]", this.pos);
+        throw new ParseError(
+          "Expected ]",
+          this.pos,
+          this.schemaString,
+          this.input,
+        );
       }
     }
 
@@ -405,7 +466,12 @@ class ValueParser {
 
       if (hasOpenBracket) {
         if (!this.consumeStr("]")) {
-          throw new ParseError("Expected ]", this.pos);
+          throw new ParseError(
+            "Expected ]",
+            this.pos,
+            this.schemaString,
+            this.input,
+          );
         }
       }
 
@@ -433,13 +499,23 @@ class ValueParser {
   }
 }
 
-export function parseValue(schema: Schema, valueString: string): unknown {
-  const parser = new ValueParser(valueString.trim());
+export function parseValue(
+  schema: Schema,
+  valueString: string,
+  schemaString?: string,
+): unknown {
+  const sStr = schemaString || schemaToTypeString(schema);
+  const parser = new ValueParser(valueString.trim(), sStr);
   const allowOmitBrackets = schema.type === "tuple" || schema.type === "array";
   const value = parser.parseValue(schema, allowOmitBrackets);
 
   if (parser.getPosition() < parser.getInputLength()) {
-    throw new ParseError("Unexpected input after value", parser.getPosition());
+    throw new ParseError(
+      "Unexpected input after value",
+      parser.getPosition(),
+      sStr,
+      valueString.trim(),
+    );
   }
 
   return value;