Rulesets for table-based function params by Rider-Linden · Pull Request #86 · secondlife/slua

Rider-Linden · 2026-06-04T17:15:08Z

Generates a lua interface for functions requiring structured lists of parameters with an initial implementation for ll.ParticleSystem as a POC.

Setting to draft for the moment for comments.
Requires 143

Related PRs:

secondlife/lsl-definitions#143
https://github.com/secondlife/server/pull/2574

local def = {
    emissive = true,
    target_linear = true,
    pattern = PSYS_SRC_PATTERN_EXPLODE,
    start_color = vector(0, 0, 1),
    src_max_age = 10,
    burst_rate = 0.1,
    burst_count = 10,
    target_key = ll.GetOwner()
}

llparticle.ParticleParams.new(def):apply()


local p = llparticle.ParticleParams.new()
-- p.flags = PSYS_PART_INTERP_COLOR_MASK
p.interp_color = true
p.emissive = true
p.pattern = PSYS_SRC_PATTERN_EXPLODE
p.start_color = vector(1, 0, 0)
p.end_color = vector(0, 1, 0)
p.start_alpha = 1.0
p.end_alpha = 1.0
p.src_max_age = 5.0
p.burst_rate = 0.1
p.burst_count = 10
p.burst_radius = 2
p:apply(2)        -- calls ll.ParticleSystem(rules)


print( `emissive = {p.emissive}` )
print(lljson.encode(p))

Copilot

Pull request overview

Adds a reusable “fluent builder” serialization layer to turn Lua parameter tables into deterministic tag/value rule lists, with initial coverage for particle-system style parameters and collection-valued params.

Changes:

Introduces llfluent_builder (C++ implementation + public header) for descriptor-driven table→rules-list serialization, including flag-bit merging and collection semantics.
Adds conformance tests exercising particle rule serialization and collection serialization.
Updates build packaging/tooling inputs (CMake sources, staged headers, definitions bundle version, and a few build scripts/ignores).

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
VM/src/llfluent_builder.cpp	New fluent-builder implementation: descriptor sorting, flag merging, and table serialization into rules lists.
VM/include/llfluent_builder.h	Public API for building fluent-builder descriptor defs and registering fluent functions.
tests/SLConformance.test.cpp	Adds harness wiring + new test cases that register mock fluent functions and validate serialized output.
tests/conformance/llprim_particle.lua	New Lua conformance test validating particle param/flag serialization behavior.
tests/conformance/fluent_builder_collection.lua	New Lua conformance test validating collection semantics serialization.
Sources.cmake	Wires new fluent-builder sources into the VM build.
init_debian_buster.sh	Updates toolchain alternatives and git safe.directory setup in the Debian buster init script.
builtins.txt	Updates bundled LSL definitions output (parameter naming and added constants).
build-cmd.sh	Stages `llfluent_builder.h` into the build artifacts include set.
autobuild.xml	Bumps `lsl_definitions` dependency version and associated archive hash/url.
.gitignore	Ignores `*.tar.bz2` artifacts.

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monty-linden

Small asks here:

C++ include conventions
Comments to warn about hazards

Additional comments for consideration.

monty-linden · 2026-07-01T04:11:13Z

+assert(#r == 0, "csv nil: output should be empty")
+
+-- Array index order is preserved in the CSV.
+r = apply({ whitelist = {"first", "second", "third"} })


When unit testing something like this, maybe not have entries in lexical order.

monty-linden · 2026-07-01T04:25:40Z

@@ -0,0 +1,61 @@
+#pragma once
+#include <stddef.h>


<cstddef> for c++

monty-linden · 2026-07-01T04:28:54Z

+#include <string>
+#include <vector>
+#include <unordered_map>
+#include <algorithm>


System before application includes.

monty-linden · 2026-07-01T04:31:32Z

+    int         field_tag;  // tag of the integer field holding the bits, e.g. 0 for "flags"
+};
+
+// Opaque handle — definition lives in llfluent_builder.cpp.


Not really an opaque. That would be 'void *' with casting. This is forward declaration/incomplete definition.

monty-linden · 2026-07-01T04:48:46Z

+
+struct FluentParamDescriptor
+{
+    const char* name;     // effective property name (pretty alias or strict fallback)


Not owned storage, correct? Owner of FPD needs to guarantee safety. Normally, would consider this and the other occurrences a hazard. This might be short-lived temporary state which allows you to handwave it off, but still. Wondering if 'constexpr'ing these could actually be used to give safety.

The generator constructs these as

static const FluentParamDescriptor [] = { }

and they are owned by the imbedding process, in our case the simulator.. There is never a case where one would be created dynamically.

I've updated the comment for fluent_builder_def_build to call for static storage.

I see this done in one or two other locations in VM/include. It's generally poor programming. But can be okay when it's used to point to const, read-only memory. I.e. compile-time text constants or constexprs. That wasn't the case here. It was really just duplicating c_str() in another form and requiring more memory.

monty-linden · 2026-07-01T05:04:41Z

+        def->names[i] = descs[i].name;
+        def->descs[i] = descs[i];
+        def->descs[i].name = def->names[i].c_str();
+    }


Here and below with the moves... we have tons of live pointers into other objects that must not be reallocated in any way or those pointers become invalid. Lay down some clear comments for the next developer if we're going to do this kind of hazard.

Your comment above gave me an idea for a refactor.

These structures all have static const lifetimes.

monty-linden · 2026-07-01T05:05:57Z

+    for (int i = 0; i < (int)count; ++i)
+        def->name_to_index[def->descs[i].name] = i;


Now that we have a sorted list, we could probably binary search it faster than the amortized cost of a small unordered map. (Not a serious request but vector beats everything at small numbers.)

I think these got left in from an earlier pass... I've removed them.

monty-linden

It's late and I'm tired and hot. So not a particularly good review. I like that there's less code. Green light but with a few questions/nits.

monty-linden · 2026-07-02T05:54:33Z

+
+struct FluentParamDescriptor
+{
+    const char* name;     // effective property name (pretty alias or strict fallback)


I see this done in one or two other locations in VM/include. It's generally poor programming. But can be okay when it's used to point to const, read-only memory. I.e. compile-time text constants or constexprs. That wasn't the case here. It was really just duplicating c_str() in another form and requiring more memory.

monty-linden · 2026-07-02T06:06:20Z

+                            csv += s[k];
+                        }
+                    }
+                    lua_pop(L, 1);


Does this pop need to occur after lua_rawgeti() even if slua_fluent_to_string() fails?

Rider-Linden · 2026-07-02T16:30:38Z

I couldn't respond to your second comment @monty-linden:

// A note about C++20 porting.
// The const char* name fields in the descriptors must have static storage duration 
// (e.g. string literals).
// This is not enforced at compile time,
// but when moving to C++20 we can do something like the following:
//
// struct LiteralString
// {
//    consteval LiteralString(const char* p) noexcept : ptr(p) {}
//    operator const char*() const noexcept { return ptr; }
//    const char* ptr;
// };
// The consteval constructor ensures that only string literals can be used 
// to construct a LiteralString.

…functions requiring lists.

Rider-Linden mentioned this pull request Jun 4, 2026

Rulesets for table-based function params secondlife/lsl-definitions#143

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Rider-Linden requested a review from Copilot July 1, 2026 00:22

Copilot started reviewing on behalf of Rider-Linden July 1, 2026 00:22 View session

Copilot AI reviewed Jul 1, 2026

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Rider-Linden marked this pull request as ready for review July 1, 2026 00:39

monty-linden requested changes Jul 1, 2026

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Rider-Linden force-pushed the rider/fluent branch from f06cef8 to 318c1b8 Compare July 1, 2026 18:22

monty-linden approved these changes Jul 2, 2026

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Add rulesets for generating table based way of passing parameters to …

bb194f6

…functions requiring lists.

Rider-Linden force-pushed the rider/fluent branch from c9ca524 to bb194f6 Compare July 2, 2026 21:59

		for (int i = 0; i < (int)count; ++i)
		def->name_to_index[def->descs[i].name] = i;

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Rider-Linden commented Jul 2, 2026

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Rider-Linden commented Jun 4, 2026 •

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