forked from defunkt/ReefVM
113 lines
2.9 KiB
TypeScript
113 lines
2.9 KiB
TypeScript
import { test, expect } from "bun:test"
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import { VM, toBytecode } from "#reef"
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test("REPL mode - demonstrates PC reset problem", async () => {
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// Track how many times each line executes
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let line1Count = 0
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let line2Count = 0
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// Line 1: Set x = 5, track execution
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const line1 = toBytecode([
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["LOAD", "trackLine1"],
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["PUSH", 0],
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["PUSH", 0],
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["CALL"],
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["POP"],
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["PUSH", 5],
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["STORE", "x"]
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])
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const vm = new VM(line1, {
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trackLine1: () => { line1Count++; return null },
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trackLine2: () => { line2Count++; return null }
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})
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await vm.run()
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expect(vm.scope.get("x")).toEqual({ type: "number", value: 5 })
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expect(line1Count).toBe(1)
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expect(line2Count).toBe(0)
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// Line 2: Track execution, load x
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const line2 = toBytecode([
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["LOAD", "trackLine2"],
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["PUSH", 0],
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["PUSH", 0],
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["CALL"],
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["POP"],
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["LOAD", "x"]
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])
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// Append line2 bytecode to VM (what a REPL would do)
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vm.instructions.push(...line2.instructions)
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for (const constant of line2.constants) {
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if (!vm.constants.includes(constant)) {
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vm.constants.push(constant)
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}
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}
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// Current behavior: run() resets PC to 0, re-executing everything
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await vm.run()
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// PROBLEM: Line 1 ran AGAIN (count is now 2, not 1)
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// This is the issue for REPL - side effects run multiple times
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expect(line1Count).toBe(2) // Ran twice! Should still be 1
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expect(line2Count).toBe(1) // This is correct
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// What we WANT for REPL:
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// - Only execute the NEW bytecode (line 2)
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// - line1Count should stay at 1
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// - line2Count should be 1
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})
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test("REPL mode - continue() executes only new bytecode", async () => {
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// Track how many times each line executes
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let line1Count = 0
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let line2Count = 0
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// Line 1: Set x = 5, track execution
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const line1 = toBytecode([
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["LOAD", "trackLine1"],
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["PUSH", 0],
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["PUSH", 0],
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["CALL"],
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["POP"],
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["PUSH", 5],
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["STORE", "x"]
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])
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const vm = new VM(line1, {
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trackLine1: () => { line1Count++; return null },
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trackLine2: () => { line2Count++; return null }
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})
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await vm.run()
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expect(vm.scope.get("x")).toEqual({ type: "number", value: 5 })
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expect(line1Count).toBe(1)
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expect(line2Count).toBe(0)
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// Line 2: Track execution, load x and add 10
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const line2 = toBytecode([
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["LOAD", "trackLine2"],
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["PUSH", 0],
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["PUSH", 0],
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["CALL"],
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["POP"],
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["LOAD", "x"],
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["PUSH", 10],
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["ADD"]
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])
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// Append line2 bytecode to VM using the helper method
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vm.appendBytecode(line2)
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// SOLUTION: Use continue() instead of run() to resume from current PC
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await vm.continue()
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const result = vm.stack[vm.stack.length - 1]
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// SUCCESS: Line 1 only ran once, line 2 ran once
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expect(line1Count).toBe(1) // Still 1! Side effect didn't re-run
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expect(line2Count).toBe(1) // Ran once as expected
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expect(result).toEqual({ type: "number", value: 15 }) // 5 + 10
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})
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