objectscript-fewshot-fixes

ObjectScript Fix Examples

HOW TO USE THESE: Before generating any fix, first identify which pattern matches the bug, state the root cause explicitly, THEN generate the fix. Research shows this "identify-then-fix" order reduces errors by ~15%.

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EXAMPLE 1: Quit-in-Loop Returns Wrong Value

BUGGY CODE:

ClassMethod IsNameUnique(name As %String, existingNames As %ListOfDataTypes) As %Boolean
{
    For i=1:1:existingNames.Count() {
        If (existingNames.GetAt(i) = name) {
            Quit 1
        }
    }
    Quit 0
}

BUG PATTERN: Quit value inside a For loop exits the loop, not the method. ROOT CAUSE: After Quit 1, execution continues AFTER the loop — the method returns the value of Quit 0 at the bottom, or empty string if Quit had a value (IRIS-specific). The return values are also logically swapped (found = not unique = should return 0).

FIXED CODE:

ClassMethod IsNameUnique(name As %String, existingNames As %ListOfDataTypes) As %Boolean
{
    For i=1:1:existingNames.Count() {
        If (existingNames.GetAt(i) = name) {
            Return 0
        }
    }
    Return 1
}

KEY RULE: Return value always exits the method. Quit value inside a loop only exits the loop.

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EXAMPLE 2: HTML Escaping Order

BUGGY CODE:

ClassMethod DisplayMessage(message As %String) As %String
{
    Set safe = $REPLACE(message, "<", "&lt;")
    Set safe = $REPLACE(safe, ">", "&gt;")
    Set safe = $REPLACE(safe, "&", "&amp;")
    Return "<div>" _ safe _ "</div>"
}

BUG PATTERN: Wrong escaping order causes double-encoding. ROOT CAUSE: Escaping < first produces <. Then escaping & turns < into < — the ampersand in the entity gets escaped again.

FIXED CODE:

ClassMethod DisplayMessage(message As %String) As %String
{
    Set safe = $REPLACE(message, "&", "&")
    Set safe = $REPLACE(safe, "<", "&lt;")
    Set safe = $REPLACE(safe, ">", "&gt;")
    Return "<div>" _ safe _ "</div>"
}

KEY RULE: Always escape & FIRST, then <, then >.

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EXAMPLE 3: SQL Missing Date Filter

BUGGY CODE:

ClassMethod SearchItems(category As %String) As %ListOfDataTypes
{
    Set results = ##class(%ListOfDataTypes).%New()
    Set stmt = ##class(%SQL.Statement).%New()
    Set sc = stmt.%Prepare("SELECT Name FROM Catalog.Item WHERE Category = ?")
    Set rs = stmt.%Execute(category)
    While rs.%Next() { Do results.Insert(rs.%Get("Name")) }
    Return results
}

BUG PATTERN: Query missing filter to exclude expired records. ROOT CAUSE: No ActiveUntil date check — returns both active and expired items. ActiveUntil = "" (NULL) means never expires; ActiveUntil < today means expired.

FIXED CODE:

ClassMethod SearchItems(category As %String) As %ListOfDataTypes
{
    Set results = ##class(%ListOfDataTypes).%New()
    Set stmt = ##class(%SQL.Statement).%New()
    Set sc = stmt.%Prepare("SELECT Name FROM Catalog.Item WHERE Category = ? AND (ActiveUntil IS NULL OR ActiveUntil >= ?)")
    Set rs = stmt.%Execute(category, +$HOROLOG)
    While rs.%Next() { Do results.Insert(rs.%Get("Name")) }
    Return results
}

KEY RULE: +$HOROLOG = today as integer. Pattern: AND (field IS NULL OR field >= ?).

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EXAMPLE 4: Forward Iteration With Removal Skips Items

BUGGY CODE:

ClassMethod ProcessItems(items As %ListOfDataTypes) As %Integer
{
    For i=1:1:items.Count() {
        If (items.GetAt(i) [ "DELETE") { Do items.RemoveAt(i) }
    }
    Return items.Count()
}

BUG PATTERN: Removing items during forward iteration causes index skipping. ROOT CAUSE: After RemoveAt(2), the old item 3 becomes item 2 — but i advances to 3, skipping the newly-shifted item.

FIXED CODE:

ClassMethod ProcessItems(items As %ListOfDataTypes) As %Integer
{
    For i=items.Count():-1:1 {
        If (items.GetAt(i) [ "DELETE") { Do items.RemoveAt(i) }
    }
    Return items.Count()
}

KEY RULE: Iterate backwards (Count():-1:1) when removing items in-place.

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EXAMPLE 5: Missing $IsObject Check After %OpenId

BUGGY CODE:

ClassMethod GetPatientAge(id As %String) As %Integer
{
    Set patient = ##class(Patient).%OpenId(id)
    Set birthYear = $PIECE(patient.DOB, "-", 1)
    Return +$EXTRACT($ZDATE($HOROLOG, 3), 1, 4) - birthYear
}

BUG PATTERN: No null check after %OpenId — crashes when record not found. ROOT CAUSE: %OpenId returns "" when ID doesn't exist. Accessing .DOB on "" causes <INVALID OREF> runtime error.

FIXED CODE:

ClassMethod GetPatientAge(id As %String) As %Integer
{
    Set patient = ##class(Patient).%OpenId(id)
    If '$IsObject(patient) { Return -1 }
    Set birthYear = $PIECE(patient.DOB, "-", 1)
    Return +$EXTRACT($ZDATE($HOROLOG, 3), 1, 4) - birthYear
}

KEY RULE: Always If '$IsObject(obj) { Return <default> } immediately after %OpenId.

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EXAMPLE 6: Postfix Quit Syntax Error

BUGGY CODE (causes #5559 parse error):

For {
    Set key = $ORDER(users(key))
    Quit:key = ""
    If ($ZCONVERT(key, "U") = searchName) { Return users(key) }
}

BUG PATTERN: Spaces in postfix condition cause parse error. ROOT CAUSE: Quit:key = "" — the space before = causes IRIS UDL parser error #5559. Postfix conditions must be written without any spaces.

FIXED CODE:

For {
    Set key = $ORDER(users(key))
    Quit:key=""
    If ($ZCONVERT(key, "U") = searchName) { Return users(key) }
}

KEY RULE: Postfix conditions: Quit:condition — NO spaces anywhere in the condition. Quit:key="" not Quit:key = "". Also never append postfix to other statements.

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EXAMPLE 7: CSV Building — O(n²) String Concat

BUGGY CODE:

ClassMethod BuildCSV(values As %ListOfDataTypes) As %String
{
    Set result = ""
    For i=1:1:values.Count() {
        If (i > 1) { Set result = result _ "," }
        Set result = result _ values.GetAt(i)
    }
    Return result
}

BUG PATTERN: O(n²) string concatenation — fails performance test for large lists. ROOT CAUSE: Each result _ value creates a new string copying all previous data. For 1000 items this copies ~500,000 total characters.

FIXED CODE:

ClassMethod BuildCSV(values As %ListOfDataTypes) As %String
{
    Set lst = ""
    For i=1:1:values.Count() {
        Set lst = lst _ $LISTBUILD(values.GetAt(i))
    }
    Return $LISTTOSTRING(lst, ",")
}

KEY RULE: Accumulate into $LIST then convert once with $LISTTOSTRING(lst, ",").

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HOW TO APPLY: Structured Fix Protocol

For every bug fix request:

1. State the bug pattern from the examples above (or identify a new one)
2. State the root cause in one sentence
3. Generate the fix based on the pattern

This structure is mandatory — stating the pattern before generating code prevents the most common errors.