docsnip

Overview ¶

Command docsnip checks that every Go code block in bide's documentation compiles against the current code, so the docs cannot drift silently when an API changes.

It reads every ```go block of the markdown files it is given (README.md and everything under docs/ by default) and type-checks each one with go/types against the packages of the Go workspace at -root, which resolves bide's own modules through go.work the way CI builds them. Export data comes from one "go list -export" run, so a warm build cache makes the check take seconds.

A block is compiled as one of:

• a complete file, when it starts with a package clause; it must compile as written;
• top-level declarations, compiled as a package of their own;
• statements, compiled as the body of a function;
• declarations (imports, types, funcs) followed by statements.

In the last three, a package the block uses as a qualifier without importing it is imported automatically when its name is unambiguous: every package of the standard library and of the workspace modules is known by name (a workspace package wins over a standard-library one, and a shorter standard-library path over a longer one). Unused variables and imports, and unused expression values (a block listing values), are allowed, since such blocks are excerpts. The elisions "{ ... }" after a space (a function body, compiled as one that panics), "T{...}" (a composite literal, compiled as T{}) and a line holding only "..." compile. A function declared without a body is an error outside an api block.

An HTML comment directly above a block (blank lines may separate them) annotates it; it does not show when the markdown is rendered:

<!-- docsnip: setup a *agent.Agent; store agent.Durable -->
<!-- docsnip: api agent -->
<!-- docsnip: skip illustrative pseudo-code -->

A setup gives the block the identifiers it uses but does not declare. Its items are separated by semicolons or newlines outside brackets: `import "path"` (or import name "path"), "returns T" (the results of the function that wraps a statement block, for a block that returns), a declaration starting with type, func, var or const, or the shorthand "name[, name] T" for a var. Errors in a setup are reported at the directive.

An api block lists declarations of one package (a name or an import path, optionally followed by "; setup items"), which is dot-imported; each declaration must match the package's own (see api.go). A skip excludes a block that is not meant to compile, with the reason; a skip on a block that compiles is reported, so the annotation is deleted once the block is real code. Blocks with identical annotation and code (the README and its translations) are compiled once, and a finding lists every copy.

Usage, from the repository root:

go run ./internal/tools/docsnip [-root dir] [-v] [path ...]

Each path is a markdown file or a directory searched for *.md files, relative to -root. The exit status is 0 when every block compiles, 1 on findings, and 2 when the check could not run.