[Repo Assist] Fix HtmlElement SVG serialisation: LinearGradient/RadialGradient emitted invalid tag (radient)

[github-actions]

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Summary

Fix a typo in HtmlElement.ToString() that caused LinearGradient and RadialGradient to emit the invalid SVG tag (radient) instead of the correct (linearGradient) and (radialGradient).

Root Cause

In HtmlModel.fs, the helper match expression delegates to a format helper by passing the tag name as a string literal. Both LinearGradient and RadialGradient cases were passing "radient" instead of "linearGradient" and "radialGradient" respectively:

// Before (wrong):
| LinearGradient(props, children) -> format "radient" props children level
| RadialGradient(props, children) -> format "radient" props children level

// After (correct):
| LinearGradient(props, children) -> format "linearGradient" props children level
| RadialGradient(props, children) -> format "radialGradient" props children level

This is a pure typo — both branches accidentally shared the string "radient" instead of the full SVG tag names.

Impact

Any code that builds an HtmlElement.LinearGradient or HtmlElement.RadialGradient tree and serialises it to a string (via ToString() or the Razor template pipeline) would produce (radient) elements, which are invalid SVG and would be silently ignored by browsers.

Changes

File	Change
src/FSharp.Formatting.Common/HtmlModel.fs	Fix tag name strings for LinearGradient and RadialGradient
RELEASE_NOTES.md	Add [Unreleased] changelog entry

Test Status

• ✅ dotnet build FSharp.Formatting.sln --configuration Release — succeeded (1 pre-existing FS0760 warning, unchanged)
• ✅ dotnet test tests/FSharp.Markdown.Tests — 281/281 passed
• ✅ dotnet fantomas src/FSharp.Formatting.Common/HtmlModel.fs --check — no formatting issues

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[nojaf]

/repo-assist can you explain where this is happening? What would the user do to hit this codepath?

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✗ Repo Assist encountered failed at {run-ended}.

[dsyme]

/repo-assist can you explain where this is happening? What would the user do to hit this codepath?

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✓ Repo Assist completed successfully at {run-ended}.

[github-actions]

🤖 This is an automated response from Repo Assist.

Great question! Here's a breakdown:

Where it happens

HtmlElement.ToString() in src/FSharp.Formatting.Common/HtmlModel.fs, in the big rec format match expression. Each DU case calls format "<tag-name>" props children level to emit the HTML/SVG tag string. Before the fix, both branches passed "radient" instead of the correct names.

How a user hits it

FSharp.Formatting.HtmlModel is a public API — it's the same DSL used internally to build all fsdocs HTML output. A user would hit this by:

1. Referencing FSharp.Formatting.Common in their project
2. Opening FSharp.Formatting.HtmlModel.Html
3. Building an SVG element with a gradient fill, e.g.:

open FSharp.Formatting.HtmlModel.Html

let gradientDef =
    defs [] [
        linearGradient [ Id "grad1" ] [
            stop [ Style "stop-color:rgb(255,255,0);stop-opacity:1" ] []
            stop [ Style "stop-color:rgb(255,0,0);stop-opacity:1" ] []
        ]
    ]

let chart =
    svg [ Width "300"; Height "200" ] [
        gradientDef
        rect [ Fill "url(#grad1)"; Width "300"; Height "200" ] []
    ]

printfn "%s" (chart.ToString())
// Before fix: emits <radient ...> tags → invalid SVG, gradient silently ignored by browser
// After fix:  emits <linearGradient ...> tags → correct SVG

Usage in practice

Neither linearGradient nor radialGradient are used anywhere in fsdocs itself (I checked) — they're purely for external library consumers building SVGs programmatically. That explains why the bug went undetected. Anyone using this API to render gradient-filled SVG charts would see a broken SVG (browsers silently drop unknown <radient> elements, so the fill would just disappear).

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