One of the motivations for this change is the following Discourse
discussion:
https://discourse.dhall-lang.org/t/offline-use-of-prelude/137
Many users have requested Dhall support for "offline" packages
that can be fetched/built/installed using ordinary package
management tools (like Nix) instead of using Dhall's HTTP import system.
I will continue to use the term "offline" to mean Dhall package
builds that do not use Dhall's language support for HTTP imports (and
instead use the package manager's support for HTTP requests, such
as `pkgs.fetchFromGitHub`)
The goal of this change is to document what is the idiomatic way to
implement "offline" Dhall builds by implementing Nixpkgs support
for such builds. That way when other package management tools ask
me how to package Dhall with their tools I can refer them to how it
is done in Nixpkgs.
This change contains a fully "offline" build for the largest Dhall
package in existence, known as "dhall-packages" (not to be confused
with `dhallPackages`, which is our Nix attribute set containing
Dhall packages).
The trick to implementing offline builds in Dhall is to take
advantage of Dhall's support for semantic integrity checks. If an
HTTP import is protected by an integrity check and a cached build
product matches the integrity check then the HTTP import is never
resolved and the expression is instead fetched from cache.
By "installing" dependencies in a pre-seeded and isolated cache
we can replace remote HTTP imports with dependencies that have
been built and supplied by Nix instead.
The offline nature of the builds are enforced by compiling the
Haskell interpreter with the `-f-with-http` flag, which disables
the interpreter's support for HTTP imports. If a user forgets
to supply a necessary dependency as a Nix build product then the
build fails informing them that HTTP imports are disabled.
By default, built packages are "binary distributions", containing
just a cache product and a Dhall expression which can be used to
resolve the corresponding cache product.
Users can also optionally enable a "source distribution" of a package
which already includes the equivalent fully-evaluated Dhall code (for
convenience), but this is disabled by default to keep `/nix/store`
utilization as compact as possible.
Some display managers (e.g. SDDM) set the XDG_CURRENT_DESKTOP variable accroding to this parameter.
If this variable is not defined, there will be some problems (e.g. MATE doesn't have icons on the desktop).
Fixes https://github.com/NixOS/nixpkgs/issues/71427
This version is 5 commits ahead of version 1.0.0 because we need at
least one patch [0] that prevents CMake from trying to use Git to fetch
the already fetched submodule...
Also some files have the wrong formatting (CRLF line endings) which
makes the patching really messy. At this point is seems therefore better
to use the master version instead (1.0.0 is pretty broken regarding
CMake).
[0]: 0ca73ee30e
3c74e48d9c8dbcede89a72ea18cd27def4b498a9 was a bit too much, it updated
permissions of all files recursively, causing files to be readable by
the group.
This isn't a problem immediately after bootup, but on a new activation,
as tmpfiles.d get restarted then, updating the permission bits of
now-existing files.
This updates the `Z` to be a `z` (the non-recursive variant), and adds a
`d` to ensure a directory is created (which should be covered by the
initrd shell script anyway)
If someone really wants to opt into telemetry, they can do so by setting
`enableTelemetry` to `true` (the default is `false`), in which case the wrapper
that sets `SAM_CLI_TELEMETRY` to `0` will not be created.
Note that this actually allows a user to optionally disable telemetry from the
command line or the (poorly documented) configuration in
`~/.aws-sam/metadata.json`. The downside is telemetry will be enabled at least
on the first run, causing a unique installation ID to be saved in the
configuration file.
