Manual fetch

Problem

What becomes confusing, fragile, or impossible without understanding manual fetch? This lesson answers that through explanation, a worked example, two runnable exercises, and a reference solution. No teacher-supplied worksheet is required.

HTTP and hypertext scale by exchanging representations through standardized methods, status codes, headers, links, and forms.

Concept explanation

Manual fetch belongs to “Earn HTMX by comparison”. HTMX earns its place only when it removes synchronization code without weakening HTTP semantics. This lesson turns manual fetch into a working part of weekly fixture.

For manual fetch, trace concrete input, state transition, output, and failure through a request/response contract whose method, status, headers, representation, and next actions are observable.

A client sends a request; a server returns a representation plus metadata. Hypermedia controls advertise valid next actions. Apply that model to supplied normal, boundary, and failure cases; each case below names its input and expected evidence.

Example bank

Compare normal, boundary, failure, and cross-layer cases. Predict each observation before revealing the explanation.

Worked example

Start from supplied lab.sh. Focus: Build manual fetch around this exact fixture: Implement same form workflow as full-page HTML, fetch, and HTMX variants.

1. Run: chmod +x lab.sh && ./lab.sh
2. Save baseline evidence. Compare curl -v output, request method, status, cache metadata, redirects, and representation bytes.
3. Boundary case: Add manual fetch support for weekly boundary case: Disable script and compare baseline recovery.
4. Failure case: Make manual fetch surface—not hide—this failure: Return 500 during partial update and inspect user-visible state.

RESULT
manual fetch handles baseline and boundary while preserving this observable result: Comparison counts code, requests, failure paths, focus behavior, and server contract for each variant. Starter-level baseline: headers.txt begins with an HTTP status line; body.txt contains the representation; byte count is greater than zero.

Starter material

Create lab.sh, paste this exact content, then run the command below.

#!/usr/bin/env sh
set -eu
url="${1:-https://example.com/}"
printf '%s\n' '# manual fetch'
curl -sS -D headers.txt -o body.txt "$url"
sed -n '1,12p' headers.txt
printf 'body bytes: ' && wc -c < body.txt

STOP / CLEANUPNo background process. Remove headers.txt and body.txt only after saving evidence.

Independent exercise

Add one real case: manual fetch

1. Create second case from blank file: Add manual fetch support for weekly boundary case: Disable script and compare baseline recovery.
2. Then create controlled failure: Make manual fetch surface—not hide—this failure: Return 500 during partial update and inspect user-visible state.
3. Use curl · Chromium Network · server logs to prove behavior, then repair controlled failure.
4. Compare result against supplied acceptance checks and reference approach before marking complete.

Expected result

• manual fetch handles baseline and boundary while preserving this observable result: Comparison counts code, requests, failure paths, focus behavior, and server contract for each variant.
• headers.txt begins with an HTTP status line; body.txt contains the representation; byte count is greater than zero.
• Controlled manual fetch failure produces captured evidence; repair restores stated invariant without hiding error.

Hints

Solution

Attempt both exercises before opening reference approach.