docs: Add GOTO keyword documentation with migration guidance to ON patterns

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Rodrigo Rodriguez (Pragmatismo) 2025-12-12 16:26:58 -03:00
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# GOTO Keyword
> ⚠️ **WARNING: GOTO is supported but NOT RECOMMENDED**
>
> While GOTO works for backward compatibility, you should use **event-driven patterns with the ON keyword** instead. GOTO makes code harder to maintain and debug.
## Syntax
```basic
label:
' statements
GOTO label
IF condition THEN GOTO label
```
## Description
`GOTO` transfers program execution to a labeled line. Labels are identifiers followed by a colon (`:`) at the start of a line.
**This keyword exists for backward compatibility only.** Modern General Bots code should use:
- `ON INSERT/UPDATE/DELETE OF` for event-driven programming
- `WHILE ... WEND` for loops
- `FOR EACH ... NEXT` for iteration
- `SUB` / `FUNCTION` for code organization
---
## ❌ OLD WAY vs ✅ NEW WAY
### Polling Loop (Don't Do This)
```basic
' ❌ BAD: GOTO-based polling loop
mainLoop:
leads = FIND "leads", "processed = false"
FOR EACH lead IN leads
CALL processLead(lead)
NEXT lead
WAIT 5
GOTO mainLoop
```
### Event-Driven (Do This Instead)
```basic
' ✅ GOOD: Event-driven with ON keyword
ON INSERT OF "leads"
lead = GET LAST "leads"
score = SCORE LEAD lead
IF score.status = "hot" THEN
TALK TO "whatsapp:" + sales_phone, "🔥 Hot lead: " + lead.name
END IF
END ON
```
---
## Why ON is Better Than GOTO
| Aspect | GOTO Loop | ON Event |
|--------|-----------|----------|
| **Efficiency** | Polls constantly, wastes CPU | Triggers only when data changes |
| **Code clarity** | Spaghetti code, hard to follow | Clear cause-and-effect |
| **Resource usage** | Always running | Idle until triggered |
| **Scalability** | Degrades with more data | Handles scale naturally |
| **Debugging** | Hard to trace execution | Clear event flow |
| **LLM integration** | Poor | Works well with TOOLs |
---
## If You Must Use GOTO
For legacy code migration or specific use cases, GOTO is supported:
### Simple Loop
```basic
counter:
TALK "Count: " + x
x = x + 1
IF x < 5 THEN GOTO counter
TALK "Done!"
```
### Multiple Labels
```basic
start:
TALK "Starting..."
GOTO process
error:
TALK "An error occurred"
GOTO cleanup
process:
result = DO_SOMETHING
IF result = "error" THEN GOTO error
TALK "Success!"
GOTO cleanup
cleanup:
TALK "Cleaning up..."
```
### Conditional GOTO
```basic
check:
IF temperature > 30 THEN GOTO too_hot
IF temperature < 10 THEN GOTO too_cold
TALK "Temperature is comfortable"
GOTO done
too_hot:
TALK "Warning: Too hot!"
GPIO SET fan_pin, HIGH
GOTO done
too_cold:
TALK "Warning: Too cold!"
GPIO SET heater_pin, HIGH
GOTO done
done:
TALK "Check complete"
```
---
## How GOTO Works Internally
GOTO is **not native to the Rhai engine**. General Bots transforms GOTO-based code into a state machine:
```basic
' Your code:
loop:
x = x + 1
IF x < 3 THEN GOTO loop
TALK "Done"
```
```basic
' Transformed internally to:
let __goto_label = "loop"
while __goto_label != "__exit" {
if __goto_label == "loop" {
x = x + 1
if x < 3 { __goto_label = "loop"; continue; }
TALK "Done"
__goto_label = "__exit"
}
}
```
This transformation:
- Adds overhead compared to native loops
- Has a safety limit of 1,000,000 iterations to prevent infinite loops
- Emits warnings in the server logs recommending ON patterns
---
## Limitations
| Limitation | Description |
|------------|-------------|
| **No computed GOTO** | `GOTO variable` is not supported |
| **No GOSUB** | Use `SUB` / `CALL` instead |
| **No line numbers** | Only named labels are supported |
| **Performance** | Slower than native WHILE loops |
| **Iteration limit** | Maximum 1,000,000 iterations per GOTO loop |
---
## Migration Guide
### From GOTO Loop to WHILE
```basic
' Before (GOTO):
start:
TALK "Hello"
x = x + 1
IF x < 10 THEN GOTO start
' After (WHILE):
WHILE x < 10
TALK "Hello"
x = x + 1
WEND
```
### From GOTO Loop to ON Event
```basic
' Before (GOTO polling):
checkOrders:
orders = FIND "orders", "status = 'new'"
FOR EACH order IN orders
CALL processOrder(order)
NEXT order
WAIT 10
GOTO checkOrders
' After (ON event):
ON INSERT OF "orders"
order = GET LAST "orders"
IF order.status = "new" THEN
CALL processOrder(order)
END IF
END ON
```
### From GOTO Error Handling to ON ERROR
```basic
' Before (GOTO):
result = RISKY_OPERATION
IF result = "error" THEN GOTO handleError
TALK "Success"
GOTO done
handleError:
TALK "Failed!"
done:
' After (ON ERROR):
ON ERROR RESUME NEXT
result = RISKY_OPERATION
IF ERROR THEN
TALK "Failed!"
ELSE
TALK "Success"
END IF
ON ERROR GOTO 0
```
---
## Best Practices
1. **Don't use GOTO for new code** - Use WHILE, FOR EACH, ON, or SUB/FUNCTION
2. **Migrate existing GOTO code** - Refactor to event-driven patterns when possible
3. **If you must use GOTO** - Keep it simple, avoid deep nesting
4. **Add comments** - Explain why GOTO is necessary
5. **Set reasonable limits** - Don't rely on the 1M iteration safety limit
---
## See Also
- [ON Keyword](./keyword-on.md) - **Recommended**: Event-driven programming
- [WHILE ... WEND](./keyword-while.md) - Loop construct
- [FOR EACH ... NEXT](./keyword-for-each.md) - Iteration
- [SUB / FUNCTION](./keyword-sub.md) - Code organization
- [ON ERROR](./keyword-on-error.md) - Error handling
---
## Summary
| Use Case | Instead of GOTO, Use |
|----------|---------------------|
| Polling for changes | `ON INSERT/UPDATE/DELETE OF` |
| Repeating code | `WHILE ... WEND` |
| Iterating collections | `FOR EACH ... NEXT` |
| Reusable code blocks | `SUB` / `FUNCTION` + `CALL` |
| Error handling | `ON ERROR RESUME NEXT` |
| Conditional branching | `IF ... ELSEIF ... ELSE ... END IF` |
| Multiple conditions | `SWITCH ... CASE ... END SWITCH` |
**The ON keyword is the future. GOTO is the past.**

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@ -84,6 +84,7 @@ See [Script Execution Flow](./script-execution-flow.md) for complete details.
| `FORMAT` | Data | Format strings and dates |
| `GENERATE PDF` | Files | Generate PDF from template |
| `GET` | Variables | Get variable or API data |
| `GOTO` | Control | Jump to label (⚠️ use ON instead) |
| `GET BOT MEMORY` | Memory | Retrieve bot-level persisted data |
| `GET USER MEMORY` | Memory | Retrieve user-level persisted data (cross-bot) |
| `GRAPHQL` | HTTP | Execute GraphQL query |