parse symbols as NewTypes

Author: TheLartians

src/newHelperTypeName.ts

@@ -3,7 +3,7 @@ import ts from "typescript";
 import { createHash } from "node:crypto";
 import { getCanonicalTypeName } from "./canonicalTypeName";
 
-export const newHelperTypeName = (state: ParserState, type: ts.Type) => {
+export const newHashedHelperTypeName = (state: ParserState, type: ts.Type) => {
   // to keep helper type names predictable and not dependent on the order of definition,
   // we use the first 10 characters of a sha256 hash of the type. If there is an unexpected
   // collision, we fallback to using an incrementing counter.
@@ -23,3 +23,19 @@ export const newHelperTypeName = (state: ParserState, type: ts.Type) => {
   }
   return `Ts2Py_${shortHash}`;
 };
+
+const getIndexedName = (i: number, prefix: string) => `Ts2Py_${prefix}_${i}`;
+
+export const newIndexedHelperTypeName = (
+  state: ParserState,
+  type: ts.Type,
+  prefix: string,
+) => {
+  let i = 0;
+  while (state.helperTypeNames.has(getIndexedName(i, prefix))) {
+    i += 1;
+  }
+  const name = getIndexedName(i, prefix);
+  state.helperTypeNames.set(name, type);
+  return name;
+};

src/parseInlineType.ts

@@ -1,6 +1,9 @@
 import ts, { TypeFlags } from "typescript";
 import { ParserState } from "./ParserState";
-import { newHelperTypeName } from "./newHelperTypeName";
+import {
+  newHashedHelperTypeName,
+  newIndexedHelperTypeName,
+} from "./newHelperTypeName";
 import { parseTypeDefinition } from "./parseTypeDefinition";
 import { getCanonicalTypeName } from "./canonicalTypeName";
 
@@ -72,9 +75,20 @@ export const tryToParseInlineType = (
     // there is no way to represent template literals in Python,
     // so we fallback to string
     return "str";
-  } else if (type.flags & TypeFlags.ESSymbol) {
-    state.imports.add("Any");
-    return "Any";
+  } else if (type.flags & TypeFlags.ESSymbolLike) {
+    const knownType = state.knownTypes.get(type);
+    if (state.knownTypes.has(type)) {
+      return knownType;
+    } else {
+      // we must create a new type to represent the symbol
+      state.imports.add("NewType");
+      const name = newIndexedHelperTypeName(state, type, "symbol");
+      state.statements.push(
+        `${name} = NewType(${JSON.stringify(name)}, object)`,
+      );
+      state.knownTypes.set(type, name);
+      return name;
+    }
   } else {
     // assume interface or object, we need to create a helper type
     if (!globalScope) {
@@ -85,7 +99,7 @@ export const tryToParseInlineType = (
         return semanticallyIdenticalType;
       } else {
         // we must create a new type
-        const helperName = newHelperTypeName(state, type);
+        const helperName = newHashedHelperTypeName(state, type);
         parseTypeDefinition(state, helperName, type);
         state.knownTypes.set(canonicalName, helperName);
         return helperName;

src/testing/basic.test.ts

@@ -62,7 +62,10 @@ describe("transpiling basic types", () => {
       "from typing_extensions import Union\n\nT = Union[None,float]",
     ],
     ["export type T = `a.b.${string}`", "T = str"],
-    ["export type T = symbol", "from typing_extensions import Any\n\nT = Any"],
+    [
+      "export type T = symbol",
+      'from typing_extensions import NewType\n\nTs2Py_symbol_0 = NewType("Ts2Py_symbol_0", object)\n\nT = Ts2Py_symbol_0',
+    ],
   ])("transpiles %p to %p", async (input, expected) => {
     const result = await transpileString(input);
     expect(result).toEqual(expected);
@@ -93,4 +96,21 @@ describe("transpiling basic types", () => {
     expect(result).not.toContain("exported");
     expect(result).toContain("Exported = float");
   });
+
+  it("re-uses existing symbol definitions", async () => {
+    const result = await transpileString(`
+      const a = Symbol("a") 
+      const b = Symbol("b") 
+      export type T1 = symbol;
+      export type T2 = symbol;
+      export type T3 = typeof a; 
+      export type T4 = symbol; 
+      export type T5 = typeof b; 
+    `);
+    expect(result).toContain(`T1 = Ts2Py_symbol_0`);
+    expect(result).toContain(`T2 = Ts2Py_symbol_0`);
+    expect(result).toContain(`T3 = Ts2Py_symbol_1`);
+    expect(result).toContain(`T4 = Ts2Py_symbol_0`);
+    expect(result).toContain(`T5 = Ts2Py_symbol_2`);
+  });
 });