ZacharyZhang-NY
e74dafcd36
Three independently ugly bugs that all fed the same log flood:
* Electron's `WebFrameMain.send` writes every "Render frame was disposed"
to stderr via `console.error`. When the worker fans a second
agent-event past a reloading renderer, we produced thousands of
identical lines and stalled the main loop on stderr I/O. Added a
`mainFrame.detached` guard so the send is short-circuited before
Electron's own catch block fires, and installed a targeted filter in
`suppress-warnings.ts` (now actually imported from the entry point)
so the specific `console.error("Error sending from webFrameMain:"…)`
noise never reaches the terminal. Any other payload still surfaces.
* `dispatchAgentMessage` accepted the human-reader sentinel as a wake
target when an agent replied to `__board__` — `wakeAgentIfPossible`
then called `db.getAgent("__board__")`, threw, and the dispatcher
kept repeating on every send. Strip `HUMAN_SENDER_ID` at
`resolveMessageWakeTargets`, and keep a defense-in-depth guard in the
heartbeat so a stray caller (future automation fan-out) cannot
reintroduce the crash.
* Pi's skills loader rejects any SKILL.md whose frontmatter `name`
diverges from its parent directory. The four bundled `my-writing-style`
copies declared `name: writing-style-skill`, so every install emitted
a warning and dropped the skill. They also lived as orphan gitlinks
(mode 160000 without .gitmodules), and the global `*.md` gitignore
hid every other SKILL.md from version control. Fixed the frontmatter
to match the dir, converted the dangling submodules to plain trees,
and allowlisted `builtin-skills/**/*.md` so a fresh clone carries the
catalogue instead of silently losing it.
79 lines
2.2 KiB
Markdown
79 lines
2.2 KiB
Markdown
---
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title: Avoid Returning and Passing Null
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impact: HIGH
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impactDescription: eliminates NullPointerException risk
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tags: err, null, optional, null-object
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---
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## Avoid Returning and Passing Null
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Returning null creates work for callers and invites errors. One missing null check leads to NullPointerException. Throw exceptions, return empty collections, or use the Special Case / Null Object pattern.
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**Incorrect (returning null):**
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```java
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public List<Employee> getEmployees() {
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if (thereAreNoEmployees) {
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return null; // Caller must check for null
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}
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return employees;
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}
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// Every caller must do this
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List<Employee> employees = getEmployees();
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if (employees != null) { // Easy to forget
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for (Employee e : employees) {
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pay(e);
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}
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}
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// Passing null
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public double calculatePay(Employee employee, Money bonus) {
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// What if bonus is null?
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}
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calculatePay(employee, null); // What does null mean?
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```
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**Correct (avoid null entirely):**
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```java
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// Return empty collection instead of null
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public List<Employee> getEmployees() {
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if (thereAreNoEmployees) {
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return Collections.emptyList();
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}
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return employees;
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}
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// Clean caller code
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for (Employee e : getEmployees()) {
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pay(e);
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}
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// Use Optional for truly optional values
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public Optional<Employee> findById(Long id) {
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return Optional.ofNullable(employeeMap.get(id));
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}
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// Use Special Case object
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public interface BillingPlan {
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Money getRate();
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}
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public class NullBillingPlan implements BillingPlan {
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public Money getRate() {
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return Money.ZERO;
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}
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}
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// Explicit parameters instead of null
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public double calculatePay(Employee employee, Money bonus) { /* ... */ }
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public double calculatePayWithoutBonus(Employee employee) { /* ... */ }
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```
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**When null/nullable is acceptable:**
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- Language-level nullable types with compiler enforcement (Kotlin `?`, TypeScript `strictNullChecks`, Rust `Option<T>`) make null safe because the compiler forces handling. The problem is untracked nullability, not the concept itself.
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- Interop with APIs or frameworks that require null (e.g., JDBC, some serialization libraries).
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Reference: [Clean Code, Chapter 7: Error Handling](https://www.oreilly.com/library/view/clean-code-a/9780136083238/)
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