feat(highcharts): implement waterfall-basic

[github-actions]

Implementation: waterfall-basic - python/highcharts

Implements the python/highcharts version of waterfall-basic.

File: plots/waterfall-basic/implementations/python/highcharts.py

Parent Issue: #777

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🤖 impl-generate workflow

[claude]

AI Review - Attempt 1/3

Image Description

Light render (plot-light.png): The plot renders as a blank canvas with only the warm off-white background (#FAF8F1) visible. No waterfall chart, bars, axes, labels, title, or any data visualization elements are present. The container exists but is completely empty.

Dark render (plot-dark.png): Similarly blank with the warm near-black background (#1A1A17) visible. No chart content, data visualization, axes, labels, title, or any elements are rendered. Both renders are identically empty.

Legibility verdict: FAIL — No content is visible to evaluate. The charts completely failed to render.

Score: 0/100

Category	Score	Max
Visual Quality	0	30
Design Excellence	0	20
Spec Compliance	0	15
Data Quality	0	15
Code Quality	0	10
Library Mastery	0	10
Total	0	100

Critical Failure: AR-04 (EMPTY_PLOT)

The implementation produces blank/empty PNG images with no visible content.

Root Cause Analysis

The code implements a fallback mechanism (lines 147-185) that:

1. Attempts to download Highcharts JS from CDN
2. If download fails/times out → falls back to <script src="..."> tags pointing to external CDN

Problem: Headless Chrome with file:// URLs cannot load external CDN scripts due to CORS/security restrictions. The library documentation at prompts/library/highcharts.md explicitly warns:

"IMPORTANT: Headless Chrome cannot load external CDN scripts from file:// URLs. You MUST download Highcharts JS and embed it inline."

When the fallback occurs, the CDN scripts fail to load silently, Highcharts is never defined in the browser, and the chart initialization is skipped, leaving a blank plot.

Specific Issues Found

1. AR-04 (EMPTY_PLOT): Both light and dark renders are completely blank — no waterfall chart, no bars, no axes, no labels, no title
2. Library Loading Failure: Highcharts JavaScript fails to load due to fallback mechanism using CDN links with file:// protocol
3. Incomplete Error Handling: The WebDriverWait (lines 207-211) only waits 15 seconds then sleeps 3 seconds, but if the script never loads, the timeout is inadequate
4. Missing Inline Script Guarantee: The code should always download Highcharts JS inline; the fallback should only be a last resort with logging, not silently try CDN

What Needs to be Fixed

High Priority:

1. Remove the fallback to CDN links entirely
2. Ensure Highcharts JS (and highcharts-more.js for waterfall) are always downloaded and embedded inline
3. Add explicit error handling: if download fails, raise an exception rather than silently creating a blank plot
4. Increase wait time for chart rendering (currently 3 seconds is insufficient)

Code improvements:

• Line 148: The condition if highcharts_js and highcharts_more_js: should enforce this is mandatory, not optional
• Lines 167-185: Remove the fallback CDN HTML template — it will never work with file://
• Add logging/assertions to verify downloads succeeded before proceeding

Weaknesses

• Highcharts JavaScript fails to load in headless Chrome environment
• Fallback mechanism silently fails instead of raising an error
• No validation that required scripts downloaded successfully
• Insufficient wait time for chart rendering

Verdict: REJECTED

Score: 0/100 — Implementation produces completely blank plots. The chart fails to render due to Highcharts library not loading. This is a critical runtime failure that must be fixed before the implementation can be evaluated for quality.

Next steps: Fix the Highcharts loading mechanism to ensure scripts are always downloaded inline and properly validated before chart initialization.

[github-actions]

🔧 AI Review Produced No Score — Auto-Retrying

The Claude Code Action ran but didn't write quality_score.txt. Auto-retrying review once...

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🤖 impl-review

[claude]

AI Review - Attempt 1/3

Image Description

Light render (plot-light.png): Background color is correct (#FAF8F1 warm off-white), but the plot area is completely blank. No title, axis labels, tick labels, or waterfall chart bars are visible. The page renders but no Highcharts content appears.

Dark render (plot-dark.png): Background color is correct (#1A1A17 warm near-black), but the plot area is completely blank. No title, axis labels, tick labels, or waterfall chart bars are visible. The page renders but no Highcharts content appears.

CRITICAL FAILURE: Both renders show completely empty canvases. The HTML configuration is valid, but the JavaScript does not execute, preventing any chart rendering.

Score: 0/100

Category	Score	Max
Visual Quality	0	30
Design Excellence	0	20
Spec Compliance	0	15
Data Quality	0	15
Code Quality	0	10
Library Mastery	0	10
Total	0	100

Auto-Reject Triggered

AR-04: EMPTY_PLOT — Both plot-light.png and plot-dark.png show completely blank images with no chart content.

Root Cause Analysis

The implementation attempts to download Highcharts JS from the CDN (lines 131-145). When the download fails or times out, it falls back to CDN <script src="..."> tags (lines 168-172). However, this fallback does not work with the file:// protocol used by Selenium in headless Chrome. CDN links cannot load external resources from local file:// URLs due to CORS restrictions.

Key issue: The code structure at lines 148-185 creates two different HTML templates based on whether the download succeeded. The fallback assumes CDN links will work, but they won't in headless Chrome.

Strengths

• Chart options JSON is well-formed with correct theme tokens
• Background colors are correctly set to #FAF8F1 (light) and #1A1A17 (dark)
• Title, axis labels, and data label formatters are properly configured

Weaknesses

• AR-04: Chart fails to render entirely — no waterfall bars, no axis labels, no title visible in either theme
• Fallback mechanism broken: CDN script tags do not work with file:// protocol in headless Chrome
• Missing guarantee of inline scripts: If download fails, script should still be embedded inline (with a stub or placeholder) rather than relying on broken CDN fallback
• Implementation does not follow highcharts.md critical requirement: "You MUST download Highcharts JS and embed it inline"

Issues Found

1. CRITICAL - AR-04: Empty Plot

   • Fix: Remove CDN fallback. If JS download fails, raise an exception to alert the developer. Do not attempt to load external scripts via file:// protocol.
   • Alternative: Provide a local copy of Highcharts JS in the repository or use --disable-web-resources more carefully to still allow protocol handlers to work.

2. Script Loading Strategy

   • Current: Try download → fallback to CDN (broken)
   • Fix: Try download → raise error if it fails (fail-fast approach)
   • Reason: Highcharts.js is ~500KB; headless screenshot generation requires the script to be available inline

AI Feedback for Next Attempt

The chart must render before it can be scored. The primary issue is the fallback to CDN links which cannot load in headless Chrome. Restructure the script acquisition:

1. Attempt to download Highcharts JS with error handling that explicitly catches timeouts/failures
2. Do NOT fall back to CDN links — they will not work with file:// protocol
3. If download fails after retries, raise an exception and let the pipeline know the implementation cannot run
4. Ensure both highcharts.js and highcharts-more.js are downloaded and embedded inline before passing to Selenium

Verify the fix works by running the implementation locally and confirming both plot-light.png and plot-dark.png contain visible waterfall charts with title, axis labels, and data labels.

Verdict: REJECTED

Status: Auto-reject (AR-04). Chart fails to render.
Next step: Fix the JS loading mechanism to guarantee inline script embedding and retry generation.

[github-actions]

❌ AI Review Failed (auto-retry exhausted)

The AI review action completed but did not produce valid output files. Auto-retry already tried once.

What happened:

• The Claude Code Action ran
• No quality_score.txt file was created

Manual rerun:

gh workflow run impl-review.yml -f pr_number=5746

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🤖 impl-review