[pancakereport]

Summary

Closes #140. Staff write assignment emails as plain text, and never see or write HTML. As agreed on the issue, this is plain text with variables, not Markdown.

• Writing the message: a blank line starts a new paragraph, line breaks are kept, and http(s):// links become clickable.
• The default message: lists the course, exam, room, seat, start time and duration on their own lines (Room: {{ROOM}} and so on), so staff can see and edit each one.
• Two versions of every email, both built from what staff wrote:
  • HTML version: rendered by a Jinja template kept in the repo.
  • Plain-text version: real text. Before, it was the raw HTML source.
  • No checkbox: the "HTML Body?" checkbox is gone, since there's nothing left to choose.
• Subject first: it comes before the message, prefilled with the exam's name ("Your Exam Seating Assignment for Midterm 1").
• Preview: shows the email the chosen student would get, filled in by the server exactly as it's sent. It shows both the HTML version and the plain-text version.
• Variables: listed at the bottom of the page, each with what it's filled in with.
• Typos are refused: a placeholder that isn't a variable ({{ROOOM}}) is refused before anything is sent. Before, it reached every student exactly as typed.

Safety

Staff text is only ever data, and is never run as a Jinja template. Running it as one would let anyone who can write an email run code on the server.

• How text reaches the template: it's split into paragraphs, line breaks, links and filled-in values, and assignment_email.html escapes each piece as it outputs it. HTML typed by staff shows up as text.
• Links: only http:// and https:// URLs become links.
• Preview: shown in a sandboxed <iframe>, so nothing in it can run scripts or reach the page.

Changes

• server/services/email/templates/:
  • __init__.py:
    • VARIABLES, one list that the page, the check and the substitution all use.
    • unknown_variables, which finds placeholders that aren't variables.
    • render_text and render_html, which build the two versions.
    • get_email, which now just returns the starting subject and body.
  • assignment_email.html: the HTML template: paragraphs, line breaks and links.
  • assignment_inform_email.txt: the default message, replacing the old .html one.
• server/services/email/__init__.py:
  • assignment_values: the values of the variables for one student.
  • substitute_about_assignment: returns the subject, text and HTML. Every send path uses it: all students, one student, test emails and the batch endpoint.
• server/forms.py: the body_html field is removed, and both subject and body are checked for unknown variables. The new EmailPreviewForm is the part of EmailForm the preview needs.
• server/views.py:
  • New endpoint: email_preview (/students/email/preview/) returns a student's email as JSON.
  • Prefill: the subject is filled in with the exam's name.
  • Single-student page: now keeps the variables in the message instead of filling them in for that student. The preview shows that student, who is preselected.
• server/templates/email.html:
  • Order: the subject, then the message with a short note on how it's formatted.
  • "Preview and send a test": one student picker shared by the preview and test emails.
  • Then: "Send to students", and the table of variables.
• server/static/css/style.css: styles for the preview, the note and the table.

Tests

• tests/unit/test_email_substitution.py: rewritten for plain text. It covers:
  • paragraphs and line breaks
  • escaping values and staff-typed HTML
  • staff text not being run as a template ({{ 7 * 7 }}, {% if %}, {{ config }})
  • which text becomes a link (trailing punctuation, parentheses, javascript:, quotes)
  • unknown variables
  • every email having a text and an HTML version
• New tests/unit/test_email_page.py: the plain-text prefill, the subject before the message, the variables table, unknown variables refused by both the page and the batch endpoint, and the preview endpoint.
• New tests/e2e/test_email_preview.py: in Chrome, Preview shows the filled-in email and its link, and a typo shows an error instead.
• Updated for the removed checkbox: test_email.py, test_email_test_send.py, test_email_batches.py and test_email_copies.py.

Locally: unit 425, e2e 17, a11y 4 passing.

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[codecov]

Codecov Report

❌ Patch coverage is 98.96907% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 80.01%. Comparing base (369643f) to head (332065d).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
server/services/email/templates/__init__.py	98.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #145      +/-   ##
==========================================
+ Coverage   79.64%   80.01%   +0.36%     
==========================================
  Files          31       31              
  Lines        2398     2442      +44     
==========================================
+ Hits         1910     1954      +44     
  Misses        488      488              

Flag	Coverage Δ
e2e	33.87% <31.95%> (+0.17%)	⬆️
unit	80.01% <98.96%> (+0.36%)	⬆️

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