affects

Forces linked blocks to be edited together. If you change this block and leave the block it points at untouched, the run fails.

Syntax

Attribute	Value	Default
affects	file:name, or :name for the same file	—

Separate multiple targets with commas:

// <block affects="README.md:supported-langs, docs/api.md:languages">

Example

src/lib.rs:

// <block affects="README.html:supported-langs">
pub enum Language {
    Rust,
    Python,
}
// </block>

README.html:

<!-- <block name="supported-langs"> -->
<ul>
    <li>Rust</li>
    <li>Python</li>
</ul>
<!-- </block> -->

Modify the enum and BlockWatch fails until you also touch supported-langs in README.html.

Direction

affects is one-way. The example above catches "code changed, docs didn't" — but not the reverse. For two-way drift detection, name both blocks and point each at the other:

// <block name="languages-code" affects="README.html:supported-langs">

<!-- <block name="supported-langs" affects="src/lib.rs:languages-code"> -->

Notes

• Diff mode only. Without a diff on stdin every block counts as unmodified, so affects can never fire. Pipe git diff --patch | blockwatch to use it. If you want a check that also works on a full-tree run, use same-as.
• Co-editing, not agreement. affects only checks that both sides were touched — it does not compare their contents. Touching the target with an unrelated edit satisfies it. When the two blocks should hold the same value, same-as is the stronger check.
• Missing targets are violations. A reference to a name that does not exist is reported.
• Targets are read, not reported. Under a diff, a target the diff did not touch is still resolved and compared, but it does not appear in a --verbosity run report. See Reports Under a Diff.
• Combining affects with check-lua gives a script access to the affected blocks' contents through ctx.affects, which is a way to compare them without file IO.

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