feat(flow editor): Format / Concat / IntToString / FloatToString palette nodes

[apotema]

Adds the four string-formatting reporter nodes (flow-codegen#26) to the flow editor palette. Closes #206. Follows the time-node palette work (#205).

What

• Palette — a "String" cluster: + Format (seeds an empty template), + Concat, + IntToString, + FloatToString.
• Reporter shape + pins — all four are reporters (rounded) with a value OUTPUT ([]const u8), no exec pins. IntToString/FloatToString take a single value input; Concat/Format take VARIADIC arg<N> inputs via a new varArgInputCount (data-input analogue of switchCaseOutputCount — renders arg0..arg<wired+1>, always one spare).
• template field — Format gets an editable template (.text widget, same as Identifier.name), round-tripping to {"type":"Format","template":"hits={d}"}.

⚠️ Intentional behavior change to EXISTING nodes (please note)

There was no per-type reporter classifier before: all .other built-ins fell through nodeVisual's else arm to the rectangular command shape — so BinOp/Compare/Logic/Literal/Identifier/GetComponent rendered as commands despite being pure-value reporters, contradicting the RFC §6 intent the code states ("reporters rounded"). The new isReporterTypeName set includes those existing expression nodes as well as the four new ones, so they now render rounded. This is deliberate: rounding only the new string reporters would leave the existing expression reporters rectangular — a worse inconsistency. Net effect: all pure-value expression nodes now share the rounded reporter silhouette; control nodes (Branch/loops/Switch/time gates) stay rectangular. Purely cosmetic, no functional/serialization change.

Tests

zig build test → 463/463 (+7 new); zig build gui-test → 26/26; zig build clean.

Parent: #187.

[cursor]

PR Summary

Low Risk
Editor-only UI and classification; intentional cosmetic rounding of existing reporter nodes with no functional or serialization impact.

Overview
Adds four string reporter nodes (Format, Concat, IntToString, FloatToString, flow-codegen#26) to the flow editor: a Text palette section, pin rendering (value in/out for scalars; dynamic arg<N> + value out for Concat/Format), and Format.template inspector editing via other_field_specs.

Variadic args mirror Switch case counting: new argIndexOf, comptime var_arg_pin_names, and varArgInputCount (wired highest arg<N> + one spare, capped at 64).

Reporter styling: new public isReporterTypeName drives rounded nodeVisual for the new types and existing expression reporters (BinOp, Literal, etc.) that previously rendered as rectangular commands — cosmetic only, no serialization change.

Exports NodeVisual, nodeVisual, and isReporterTypeName for tests. +7 unit tests cover palette seeding, pins, round-trip, and varArgInputCount.

^{Reviewed by Cursor Bugbot for commit 1997765. Bugbot is set up for automated code reviews on this repo. Configure here.}

[gemini-code-assist]

Code Review

This pull request implements support for string and text reporter nodes (Format, Concat, IntToString, and FloatToString) in the flow editor. It introduces logic to dynamically calculate and render variadic input pins (arg<N>) based on active connections, styles these nodes as rounded reporters, and adds comprehensive unit tests. The review feedback suggests improving the robustness of pin name parsing in argIndexOf by strictly validating ASCII digits, and refactoring varArgInputCount to use @max for a more idiomatic Zig implementation.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.

[gemini-code-assist]

The argIndexOf function parses the pin name suffix using std.fmt.parseInt. However, parseInt allows a leading + sign (e.g., arg+1 would parse as 1). To ensure strict correctness and prevent malformed pin names from being parsed as valid indices, we should verify that all characters in digits are ASCII digits before parsing.

pub fn argIndexOf(pin: []const u8) ?u32 {
    if (!std.mem.startsWith(u8, pin, "arg")) return null;
    const digits = pin[3..];
    if (digits.len == 0) return null;
    for (digits) |c| {
        if (!std.ascii.isDigit(c)) return null;
    }
    return std.fmt.parseInt(u32, digits, 10) catch null;
}

[apotema]

Done — argIndexOf now rejects any non-digit suffix before parseInt, so arg+1 (and other malformed forms) no longer parse. Matches caseIndexOf/codegen's isCaseExecPin.

[gemini-code-assist]

In Zig, we can write the tracking of the highest index more idiomatically by using @max and avoiding the force-unwrap highest.?.

pub fn varArgInputCount(node_id: u32, edges: []const flow_io.Edge) u32 {
    var highest: ?u32 = null;
    for (edges) |e| {
        if (e.to_node != node_id) continue;
        const idx = argIndexOf(e.to_pin) orelse continue;
        highest = if (highest) |h| @max(h, idx) else idx;
    }

[apotema]

Done — highest = if (highest) |h| @max(h, idx) else idx;, dropping the force-unwrap.

[Copilot]

Pull request overview

Adds the four string/text formatting reporter nodes to the flow editor palette and rendering logic, aligning editor visuals/pins with the existing flow-codegen contract (issue #206) and bringing .other expression nodes in line with the intended “reporters are rounded” UI rule.

Changes:

• Adds a new “Text” palette section with Format, Concat, IntToString, and FloatToString nodes (including seeding Format.template).
• Implements data-pin rendering for the new nodes, including derived variadic arg<N> inputs for Concat/Format via varArgInputCount.
• Introduces reporter classification for .other expression nodes (including the new string reporters) so they render with the rounded reporter silhouette; adds corresponding unit tests and round-trip coverage.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/modules/flow_doc.zig	Adds variadic arg-pin infrastructure, renders pins for new string reporter nodes, and classifies .other expression nodes as reporters for visuals.
src/flow_io.zig	Adds Format.template to other_field_specs so it’s editable via the inspector .text widget and round-trips correctly.
src/tests.zig	Adds tests covering creation defaults, reporter classification, variadic arg derivation, and parse/render round-tripping for the new nodes.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.