feat: implement recursive placeholder resolution in Default parameters #1013

AshokThangavel · 2025-12-30T16:51:56Z

Support Recursive Placeholder Resolution in Module Parameter

Description

This PR introduces deeply nested variables or chained configuration settings where one ${variable} depends on another.
with a safety handle complex dependencies and prevent infinite loops in the case of circular references.

fixes: #1009

Changes

Recursive Logic: Updated ResolvePlaceholders to use a while loop that continues as long as substitutions are being made.
Efficiency: The loop exits immediately if a pass results in no changes, ensuring no performance penalty for simple configurations.

Testing Performed

Unit Tests: Verified with complex nested strings:

${A} -> ${B} -> ${C} -> FinalValue.

Integration Test: Added a new integration test class Test.PM.Integration.Module that:

Generates a module.xml from XData.
Writes it to the filesystem.
Executes an IPM load command to verify the full lifecycle of the variable resolution.

Test Execution Results: `Test.PM.Integration.Module`

Counter	Action	Status	Description
1	LogMessage	passed	start Loading the demo-module1 module
2	AssertStatusOK	passed	Directory created /home/irisowner/zpm/tests/integration_tests/Test/PM/Integration/_data/varresolver/
3	AssertStatusOK	passed	module.xml File created on /home/irisowner/zpm/tests/integration_tests/Test/PM/Integration/_data/varresolver/
4	AssertStatusOK	passed	Created the xml file on /home/irisowner/zpm/tests/integration_tests/Test/PM/Integration/_data/varresolver/
5	AssertStatusOK	passed	Loaded varresolver module successfully from /home/irisowner/zpm/tests/integration_tests/Test/PM/Integration/_data/varresolver/
6	AssertTrue	passed	Module demo-module1 exists in IPM and version is 1.0.0
7	LogMessage	passed	List all modules
8	AssertStatusOK	passed	uninstalled module demo-module1 successfully.
9	AssertStatusOK	passed	Deleted the module.xml file from /home/irisowner/zpm/tests/integration_tests/Test/PM/Integration/_data/varresolver/
10	LogMessage	passed	Duration of execution: 1.193466 sec.

isc-dchui

A few comments and questions

isc-dchui · 2026-01-20T15:25:10Z

src/cls/IPM/Storage/ModuleSetting/Default.cls

+        for {
+            set param = $order(customParams(param), 1, data)
+            quit:param=""
+            continue:data'["${"


Both ${ and {$ syntax are allowed so you'll want to check for both

Thank you for pointing the syntax. I've updated the code to support both formats

isc-dchui · 2026-01-20T15:27:56Z

src/cls/IPM/Storage/ModuleSetting/Default.cls

+            continue:data'["${"
+
+            set varExpr = "${" _ $piece($piece(data, "${", 2), "}") _ "}"
+            set resolved = ##class(%IPM.Utils.Module).%EvaluateSystemExpression(varExpr)


Does this not work if you pass the whole string into %EvaluateSystemExpression and let it resolve all the expressions at once instead of just extracting the first one?

I've modified the logic to ensure the system variables and custom variables.

isc-dchui · 2026-01-20T15:37:15Z

tests/integration_tests/Test/PM/Integration/Module.cls

+    set module = ##class(%IPM.Storage.Module).NameOpen(..#ModuleName)
+    do $$$AssertTrue($isobject(module), "Module "_..#ModuleName_" exists in IPM and version is "_ module.Version.ToString())
+
+        do $$$LogMessage("List all modules")


Nit: remove extra tab

Sure, fixed the tab alignment

tests/integration_tests/Test/PM/Integration/Module.cls

src/cls/IPM/Storage/ModuleSetting/Default.cls

isc-dchui · 2026-01-20T15:44:50Z

tests/integration_tests/Test/PM/Integration/Module.cls

+			<Default Name="ipmtest" Value="TESTING MY STRING"/>
+			<Default Name="ipmdir" Value="/usr/irissys/mgr/user/mts"/>
+			<Default Name="datapath" Value="${libdir}data/" />
+			<Default Name="datapath1" Value="${ipmdir}data/" />


I'm a bit curious about how this will handle the rather pathological case of using defaults to create a new system expression from parts. So something like this:

<Default Name="start" Value="${" /> <Default Name="middle" Value="namespace" /> <Default Name="end" Value="}" /> <Default Name="frankenstein" Value="${start}${middle}${end}"/>

Thank you for pointing out that excellent scenario. You are absolutely right—this is a 'pathological' but critical edge case for configuration flexibility. I have updated the implementation.

isc-dchui · 2026-01-20T15:45:20Z

CHANGELOG.md

 - #822: The CPF resource processor now supports system expressions and macros in CPF merge files
 - #578 Added functionality to record and display IPM history of install, uninstall, load, and update
 - #961: Adding creation of a lock file for a module by using the `-create-lockfile` flag on install.
+- #1013: Implement recursive placeholder resolution in Default parameters


Move this to the new 0.10.6 section please

Thanks. I've moved to 0.10.6

-Support nested ${var} and {$var} delimiters and handled Frankenstein-case

isc-dchui

Thanks for the updates! Here's another pass of comments/questions

isc-dchui · 2026-01-23T17:06:41Z

src/cls/IPM/Storage/ModuleSetting/Default.cls

        set found = 0
-        set maxLevels = maxLevels - 1
+        //Decrement levels and check for circular references
+		if '$increment(maxLevels, -1) {


I don't think $increment will thrown an error if maxLevels <= 0. Only if it is (way) too large, so this error condition needs a bit of adjustment

The ' negation catches when $increment returns 0, which happens exactly after 20 passes. However, I'll update it to an explicit if (maxLevels <= 0) check to ensure it's more robust and readable. Thank you!

isc-dchui · 2026-01-23T17:16:17Z

src/cls/IPM/Storage/ModuleSetting/Default.cls


-            set varExpr = "${" _ $piece($piece(data, "${", 2), "}") _ "}"
-            set resolved = ##class(%IPM.Utils.Module).%EvaluateSystemExpression(varExpr)
+            set initialData = data


Hm, let me reword what I meant. Instead of all this manual parsing, can we not do something like this?

set param = $order(customParams(param), 1, data) quit:param="" //Skip if no placeholders remain continue:data'["{" set resolved=##class(%IPM.Utils.Module).%EvaluateSystemExpression(param) // and then for (key, val) in customParams, set resolved = %RegExReplace(resolved, key, val) ...

Ideally we do not duplicate the SystemExpressions into another function.

I agree. I initially considered using %EvaluateSystemExpression but opted for a local array approach to optimize the resolution process. Using a pre-fetched systemParams array avoids redundant scans and regex evaluations inside the nested loop, allowing for more efficient lookups. However, I have updated the code to invoke %EvaluateSystemExpression directly to maintain consistency with the existing API.
Thank you!

isc-dchui · 2026-01-23T17:19:46Z

CHANGELOG.md

+
+### Fixed
+- #996: Ensure COS commands execute in exec under a dedicated, isolated context
+- #1013: Implement recursive placeholder resolution in Default parameters


Should go into the "Added" section

Moved to Added section

isc-dchui · 2026-01-23T17:24:38Z

tests/integration_tests/Test/PM/Integration/Module.cls

+}
+
+/// Create class definition at runtime to capute the resovled reference value through <invoke> in manifest
+ClassMethod CreateClassdef() As %Status


I'm not sure I quite understand. Could you please explain why we need a new dynamically created class to capture frankenstein when the other defaults don't?

The reason I created this class was to verify that placeholders are correctly translated and passed to the method. Additionally I captured other variables in args... and temple global verify those variables. However, I explicitly check frankenstein for an additional layer of confirmation to ensure everything works as expected during testing. Thank you!

…xpression - Adopted %EvaluateSystemExpression for system variable resolution to align with existing APIs. - Retained multi-pass logic to handle nested and "Frankenstein" placeholders. - Implemented a priority gate: customParams take precedence over system defaults. - Hardened maxLevels condition using an explicit guard clause for better robustness.

AshokThangavel added 2 commits December 30, 2025 22:06

feat: implement recursive placeholder resolution in Default parameters

042462b

fix: update method name

0ea3b84

AshokThangavel requested review from isc-dchui, isc-egabhart, isc-eneil, isc-jili, isc-jlechtne, isc-kiyer, isc-pbarton and isc-tleavitt as code owners December 30, 2025 16:51

docs: update the CHANGELOG file

d31ed58

isc-dchui requested changes Jan 20, 2026

View reviewed changes

AshokThangavel added 4 commits January 21, 2026 00:14

Merge branch 'main' into feat/unified-variable-interpolation

40e6cb5

fix: updated the code based on feedback

f8c629b

refactor: Updated placeholder logic

c921fd7

-Support nested ${var} and {$var} delimiters and handled Frankenstein-case

fix:updated the code based on feedback

7272092

isc-dchui reviewed Jan 23, 2026

View reviewed changes

feat: implement recursive placeholder resolution in Default parameters #1013

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feat: implement recursive placeholder resolution in Default parameters #1013

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AshokThangavel commented Dec 30, 2025

Support Recursive Placeholder Resolution in Module Parameter

Description

Changes

Testing Performed

Test Execution Results: Test.PM.Integration.Module

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Test Execution Results: `Test.PM.Integration.Module`

AshokThangavel Jan 23, 2026 •

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