Tooling

Command names and options will be reviewed before the first release.

The `geng` command#

One program does everything:

Command	What it does
`geng make <Module>`	compile a program whose `main` is in `<Module>`
`geng run <Module>`	compile and run it
`geng test`	build and run the project’s tests, on its target
`geng release`	build an OTP release (BEAM only)
`geng fmt`	format source files
`geng protobuf`	generate Geng modules from `.proto` files
`geng docs`	a package’s documentation
`geng init`	create a project
`geng package ...`	install, uninstall and list outdated dependencies; validate a package; compare two versions’ interfaces (`diff`) and choose the next version number (`bump`)

geng make takes --optimize for a release build, which also refuses any use of Debug. On the native target, --debug-info keeps the generated C and compiles it for gdb, perf and gcov.

There is no REPL.

Project file: `geng.toml`#

An application:

[application]
geng = "0.6.0 <= v < 0.7.0"
runtime = "node"

[dependencies]
"github.com/geng-language/url" = "6.0.0 <= v < 7.0.0"

A package:

[package]
name = "github.com/geng-language/url"
version = "6.0.0"
summary = "Create and parse URLs."
license = "BSD-3-Clause"
geng = "0.6.0 <= v < 0.7.0"

[platform]
runtime = "any"

[modules]
exposed = ["Url", "Url.Builder", "Url.Parser", "Url.Parser.Query"]

runtime and target are described in Platforms and targets. Source files end in .geng and live under src/.

Packages#

A package is identified by a URL path, such as github.com/geng-language/url or git.example.com/team/pkg.
There is no registry. Packages are fetched directly from git, so private packages on an internal server work the same way as public ones.
Versions are resolved by minimal version selection, as in Go: the build uses the oldest version that satisfies every requirement.
geng.lock pins exact commits. A build with a lock file does not contact git, and a tag that has moved since it was locked is refused.
core comes with the compiler and is not listed as a dependency.
A [sources] table can point a package at a local path or another git location, for development.

Formatter#

geng fmt formats every file in the project, geng fmt <paths> formats those files, and geng fmt --check changes nothing and fails if any file is unformatted, for CI.

It has no options. Where a construct can be written on one line or across several (a record, an array, a list of arguments), it keeps your choice, and normalizes everything else. The compiler does not require formatted code.

Protobuf#

geng protobuf reads proto3 files and generates one Geng module per .proto file, with a decoder, an encoder and a default value for each message. Protobuf’s integer types map directly to Geng’s: int32 is Int, int64 is Int64, uint32 is UInt32, and uint64 is UInt64. The naming rules are part of the language specification, so every project generates the same names.

Editor support#

Not yet available.