Replace SimpleEvaluationProvider with ECJ compile+inject evaluator

.gitignore

@@ -40,6 +40,12 @@ tests/fixtures/c/*.dSYM
 # Java build artifacts
 *.class
 tests/fixtures/java/multi-package/out/
+src/dap/adapters/java/target/
 
 # Generated at build time
 src/dap/adapters/java/adapter-sources.tar.gz
+
+# Demo recordings & generated assets
+demo/**/recording.cast
+demo/**/__hotpatch_tmp/
+docs/java-hotpatch.gif

build.ts

@@ -1,7 +1,7 @@
 import { $ } from "bun";
 
 // Generate Java adapter sources tarball
-await $`tar czf src/dap/adapters/java/adapter-sources.tar.gz -C src/dap/adapters/java com/debugthat/adapter`;
+await $`tar czf src/dap/adapters/java/adapter-sources.tar.gz -C src/dap/adapters/java com/debugthat/adapter pom.xml`;
 
 // Bundle
 await $`bun build src/main.ts --outdir dist --target=bun`;

demo/java-hotpatch/pom.xml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>3.4.4</version>
+    </parent>
+    <groupId>com.example</groupId>
+    <artifactId>pricing-service</artifactId>
+    <version>0.0.1</version>
+
+    <properties>
+        <java.version>17</java.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+            </plugin>
+        </plugins>
+    </build>
+</project>

demo/java-hotpatch/record.sh

@@ -0,0 +1,130 @@
+#!/bin/bash
+# Demo: Java hotpatch on a Spring Boot app — fix a bug without restarting
+#
+# Prerequisites:
+#   1. cd demo/java-hotpatch && mvn -q compile
+#   2. Start Spring Boot in a separate terminal:
+#      mvn spring-boot:run -Dspring-boot.run.jvmArguments="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005"
+#   3. Record:
+#      asciinema rec recording.cast --cols 100 --rows 35 --command "bash record.sh"
+#   4. Generate GIF:
+#      agg recording.cast ../../docs/java-hotpatch.gif --theme monokai --font-size 14
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+SRC="src/main/java/com/example/PricingController.java"
+SRC_FIXED="src/main/java/com/example/PricingController.java.fixed"
+BUGGY_LINE='subtotal - discount + (discount * VAT_RATE)'
+FIXED_LINE='(subtotal - discount) * (1 + VAT_RATE)'
+
+type_cmd() {
+  local cmd="$1"
+  local delay="${2:-0.02}"
+  printf "\033[1;32m❯\033[0m "
+  for (( i=0; i<${#cmd}; i++ )); do
+    printf "%s" "${cmd:$i:1}"
+    sleep "$delay"
+  done
+  sleep 0.3
+  printf "\n"
+}
+
+run() {
+  local cmd="$1"
+  local pause_before="${2:-1}"
+  local pause_after="${3:-2}"
+  sleep "$pause_before"
+  type_cmd "$cmd"
+  eval "$cmd"
+  sleep "$pause_after"
+}
+
+comment() {
+  sleep "${2:-0.8}"
+  printf "\033[1;33m# %s\033[0m\n" "$1"
+  sleep "${3:-1}"
+}
+
+show_diff() {
+  local old="$1" new="$2"
+  diff -u "$old" "$new" | tail -n +3 | while IFS= read -r line; do
+    case "$line" in
+      @@*) ;;
+      -*) printf "\033[1;31m  - %s\033[0m\n" "${line:1}" ;;
+      +*) printf "\033[1;32m  + %s\033[0m\n" "${line:1}" ;;
+       *) printf "\033[90m    %s\033[0m\n" "$line" ;;
+    esac
+  done
+}
+
+# ── Setup ──
+cd "$SCRIPT_DIR"
+
+# Ensure buggy source is active
+sed -i '' "s|$FIXED_LINE|$BUGGY_LINE|" "$SRC" 2>/dev/null || true
+sed -i '' 's|// VAT applied to net amount (subtotal - discount)|// BUG: VAT applied to discount instead of net amount|' "$SRC" 2>/dev/null || true
+
+dbg stop 2>/dev/null
+export FORCE_COLOR=1
+
+# Verify Spring Boot is running
+if ! curl -m 2 -s localhost:8080/price > /dev/null 2>&1; then
+  echo "Error: Spring Boot is not running on port 8080."
+  echo "Start it first: mvn spring-boot:run -Dspring-boot.run.jvmArguments=\"-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005\""
+  exit 1
+fi
+
+# ── Demo starts ──
+
+comment "Spring Boot pricing API has a VAT bug. Let's hotpatch it live." 0.2 1.5
+
+# 1. Show the bug
+run "curl -s localhost:8080/price | python3 -m json.tool" 0.5 2
+comment "Total is 133.97 — expected (149.97 - 20) * 1.20 = 155.96" 0.3 1.5
+
+# 2. Attach debugger
+run "dbg attach 5005 --runtime java" 0.5 1.5
+
+# 3. Set breakpoint on the buggy line
+run "dbg break $SRC:21" 0.3 1
+
+# 4. Trigger a request (blocks at breakpoint)
+comment "Trigger a request to hit the breakpoint:" 0.3 0.8
+curl -s localhost:8080/price > /dev/null &
+sleep 3
+
+# 5. Show source with colors (paused at the bug)
+run "dbg source --lines 20" 0.3 2.5
+
+# 6. Eval to understand the bug
+run 'dbg eval "subtotal - discount + (discount * 0.20)"' 0.5 1.5
+comment "133.97 — VAT is on the discount, not the net amount" 0.3 1.5
+
+# 7. Test the correct formula
+run 'dbg eval "(subtotal - discount) * (1 + 0.20)"' 0.5 1.5
+comment "155.96 — correct! Apply the fix:" 0.3 1.5
+
+# 8. Show the diff and apply the fix
+sleep 0.5
+printf "\033[1;32m❯\033[0m "
+type_cmd "# Applying fix..."
+show_diff "$SRC" "$SRC_FIXED"
+sleep 2
+cp "$SRC_FIXED" "$SRC"
+
+# 9. Hotpatch the running JVM
+run "dbg hotpatch $SRC" 0.5 2.5
+
+# 10. Remove breakpoint and continue
+run "dbg break-rm BP#1" 0.3 0.3
+run "dbg continue" 0.3 1.5
+
+# 11. Verify — curl returns the fixed value
+comment "Service is still running. Verify:" 0.5 0.8
+run "curl -s localhost:8080/price | python3 -m json.tool" 0.5 3
+
+comment "155.96 — fixed without restarting the JVM!" 0.3 2
+
+# ── Cleanup ──
+# Restore buggy source for next demo run
+sed -i '' "s|$FIXED_LINE|$BUGGY_LINE|" "$SRC" 2>/dev/null || true
+sed -i '' 's|// VAT applied to net amount (subtotal - discount)|// BUG: VAT applied to discount instead of net amount|' "$SRC" 2>/dev/null || true

demo/java-hotpatch/show-diff.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+# Show a colored inline diff between two files, with line numbers
+# Usage: show-diff.sh <old-file> <new-file>
+
+OLD="$1"
+NEW="$2"
+
+RED='\033[1;31m'
+GREEN='\033[1;32m'
+GRAY='\033[90m'
+RESET='\033[0m'
+
+# Get unified diff, skip header lines, show context
+diff -u "$OLD" "$NEW" | tail -n +3 | while IFS= read -r line; do
+  case "$line" in
+    @@*)
+      # Extract line number from hunk header
+      ;;
+    -*)
+      printf "${RED}  - %s${RESET}\n" "${line:1}"
+      ;;
+    +*)
+      printf "${GREEN}  + %s${RESET}\n" "${line:1}"
+      ;;
+    *)
+      printf "${GRAY}    %s${RESET}\n" "$line"
+      ;;
+  esac
+done

demo/java-hotpatch/src/main/java/com/example/PricingApp.java

@@ -0,0 +1,11 @@
+package com.example;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class PricingApp {
+    public static void main(String[] args) {
+        SpringApplication.run(PricingApp.class, args);
+    }
+}

demo/java-hotpatch/src/main/java/com/example/PricingController.java

@@ -0,0 +1,31 @@
+package com.example;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+import java.util.Map;
+
+@RestController
+public class PricingController {
+
+    private static final double VAT_RATE = 0.20;
+
+    @GetMapping("/price")
+    public Map<String, Object> getPrice(
+            @RequestParam(defaultValue = "49.99") double price,
+            @RequestParam(defaultValue = "3") int qty,
+            @RequestParam(defaultValue = "20") double discount) {
+
+        double subtotal = price * qty;
+        // BUG: VAT applied to discount instead of net amount
+        double total = subtotal - discount + (discount * VAT_RATE);
+        total = Math.round(total * 100.0) / 100.0;
+
+        return Map.of(
+            "subtotal", subtotal,
+            "discount", discount,
+            "vat_rate", VAT_RATE,
+            "total", total
+        );
+    }
+}

demo/java-hotpatch/src/main/java/com/example/PricingController.java.fixed

@@ -0,0 +1,31 @@
+package com.example;
+
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+import java.util.Map;
+
+@RestController
+public class PricingController {
+
+    private static final double VAT_RATE = 0.20;
+
+    @GetMapping("/price")
+    public Map<String, Object> getPrice(
+            @RequestParam(defaultValue = "49.99") double price,
+            @RequestParam(defaultValue = "3") int qty,
+            @RequestParam(defaultValue = "20") double discount) {
+
+        double subtotal = price * qty;
+        // VAT applied to net amount (subtotal - discount)
+        double total = (subtotal - discount) * (1 + VAT_RATE);
+        total = Math.round(total * 100.0) / 100.0;
+
+        return Map.of(
+            "subtotal", subtotal,
+            "discount", discount,
+            "vat_rate", VAT_RATE,
+            "total", total
+        );
+    }
+}

package.json

@@ -37,6 +37,7 @@
     "lint": "biome check .",
     "format": "biome check --write .",
     "typecheck": "tsc --noEmit -p tsconfig.check.json",
+    "build:java": "bun run src/main.ts install java",
     "update-jsc-protocol": "curl -sL https://raw.githubusercontent.com/oven-sh/bun/main/packages/bun-inspector-protocol/src/protocol/jsc/index.d.ts -o src/cdp/jsc-protocol.d.ts"
   },
   "devDependencies": {

src/cdp/adapters/bun-adapter.ts

@@ -44,7 +44,7 @@ export class BunAdapter implements CdpDialect {
 		const entryScript = this.resolveEntryScript(session);
 		const tempBpId = await this.setEntryBreakpoint(entryScript);
 		try {
-			const waiter = session.createPauseWaiter(5_000);
+			const waiter = session.waitUntilStopped();
 			await this.jsc.send("Inspector.initialized");
 			await waiter;
 		} finally {

src/cdp/adapters/node-adapter.ts

@@ -114,7 +114,7 @@ export class NodeAdapter implements CdpDialect {
 			skips < MAX_INTERNAL_PAUSE_SKIPS
 		) {
 			skips++;
-			const waiter = session.createPauseWaiter(5_000);
+			const waiter = session.waitUntilStopped();
 			await session.cdp.send("Debugger.resume");
 			await waiter;
 		}

src/cdp/client.ts

@@ -15,6 +15,13 @@ interface PendingRequest {
 	timer: ReturnType<typeof setTimeout>;
 }
 
+export class TimeoutError extends Error {
+	constructor(message: string) {
+		super(message);
+		this.name = "TimeoutError";
+	}
+}
+
 export class CdpClient {
 	private ws: WebSocket;
 	private nextId = 1;
@@ -150,7 +157,7 @@ export class CdpClient {
 
 			const timer = setTimeout(() => {
 				cleanup();
-				reject(new Error(`waitFor timed out: ${event} (after ${timeoutMs}ms)`));
+				reject(new TimeoutError(`waitFor timed out: ${event} (after ${timeoutMs}ms)`));
 			}, timeoutMs);
 
 			const cleanup = () => {