# Templates

Contains all example source code, scaffolding, certificates and metadata used
by func when creating and building function instances.

To rebuild run `make templates` (which caches).  To force a full rebuild run
`make clean && make`

## Layout

Each directory within `templates` corresponds to a known language runtime.
The `certs` directory is a reserved word containing root SSL certificates.
Each directory within a runtime directory corresponds to a named templaate.
The `scaffolding` directory within the runtime directory is a reserved word
containing the adapter code that converts a function with a given method
signature into a service by way of the external function runtime libraries.

## Packaging

When updates are made to these templates, they must be packaged (serialized as
a Go byte array) by running `make templates` (which rebuilds
`generate/zz_filesystem_generated.go`, and checking in the resultant
`./generate/zz_filesystem_generated.go` file.

## How it works

The `./generate/templates` directory contains Go program that generates `./generate/zz_filesystem_generated.go`.
The file defines byte array variable named `TemplatesZip`.
The variable contains ZIP representation of the templates directory.
The byte array variable is then used to instantiate exported global variable `function.EmbeddedTemplatesFS`,
which implements standard Go interfaces `fs.ReadDirFS` and `fs.StatFS`.

## Rationale

Until such time as embedding static assets in binaries is included in the
base `go build` functionality (see https://github.com/golang/go/issues/35950)
we need to use our custom serialization script (`./generate/templates/main.go`).

Native Go embedding introduced in Go 1.16 could be used for executable binary,
however it cannot be used for library.
For a library we need to generate a Go source code containing the templates.