Add getComponent to project and package
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* Delays cabal configure errors until after evaluation when possible.
* Avoids rerunning long `cabal configure` if we already know it will fail.
* Provides a way to get a component from a package or project using a `cabal` like reference.
Code using the `tool` functions will automatically use `getComponent`.
For `(hackage-package {...}).components.library` is also ok.
```
# Consider changing hackage-package use from:
(pkgs.haskell-nix.hackage-package {...}).components.exes.something
(pkgs.haskell-nix.hackage-package {...}).getComponent "exe:something"
# For any cabal project:
project.hsPkgs.somepackage.components.exes.something
project.getComponent "somepackage:exe:something"
# or do it in two steps
(project.getPackage "somepackage").getComponent "exe:something"
```
The reason for the new function is that we cannot provide the attribute interface without knowing that packages are in the project first.
Here is how the `cabal configure` error output is handled:
* The `plan-nix` derivation builds even if `cabal configure` fails.
* When it fails, it copies `failed-cabal-configure.nix` to the `$out/default.nix` along with a copy of the `cabal configure` output.
* When `failed-cabal-configure.nix` is imported and used in any way it writes the `cabal configure` output with `__trace` so it will always be visible.
* Instead of a `plan` the imported nix contains a `configurationError` pointing the `cabal configure` output.
* The intermediate functions `configurationError` and bubble it up to where it is needed.
* `getPackage` returns a mostly empty proxy for a real package when there is a `configurationError`
* The `getComponent` function always returns a derivation, but the version in the proxy writes the `cabal configure` output to stdout and calls `exit 1` (so that it will never build).
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angerman
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Mar 4, 2021
# Conflicts: # lib/call-cabal-project-to-nix.nix
Ooops, that was not supposed to be in here. Fixed |
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booniepepper
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Feb 4, 2022
* Delays cabal configure errors until after evaluation when possible.
* Avoids rerunning long `cabal configure` if we already know it will fail.
* Provides a way to get a component from a package or project using a `cabal` like reference.
Code using the `tool` functions will automatically use `getComponent`.
For `(hackage-package {...}).components.library` is also ok.
```
# Consider changing hackage-package use:
(pkgs.haskell-nix.hackage-package {...}).components.exes.something
(pkgs.haskell-nix.hackage-package {...}).getComponent "exe:something"
# For any cabal project:
project.hsPkgs.somepackage.components.exes.something
project.getComponent "somepackage:exe:something"
# or do it in two steps
(project.getPackage "somepackage").getComponent "exe:something"
```
The reason for the new function is that we cannot provide the attribute interface without knowing that packages are in the project first.
Here is how the `cabal configure` error output is handled:
* The `plan-nix` derivation builds even if `cabal configure` fails.
* When it fails, it copies `failed-cabal-configure.nix` to the `$out/default.nix` along with a copy of the `cabal configure` output.
* When `failed-cabal-configure.nix` is imported and used in any way it writes the `cabal configure` output with `__trace` so it will always be visible.
* Instead of a `plan` the imported nix contains a `configurationError` pointing the `cabal configure` output.
* The intermediate functions `configurationError` and bubble it up to where it is needed.
* `getPackage` returns a mostly empty proxy for a real package when there is a `configurationError`
* The `getComponent` function always returns a derivation, but the version in the proxy writes the `cabal configure` output to stdout and calls `exit 1` (so that it will never build).
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Delays cabal configure errors until after evaluation when possible.
Avoids rerunning long
cabal configureif we already know it will fail.Provides a way to get a component from a package or project using a
caballike reference.Code using the
toolfunctions will automatically usegetComponent.For
(hackage-package {...}).components.libraryis also ok.The reason for the new function is that we cannot provide the attribute interface without knowing that packages are in the project first.
Here is how the
cabal configureerror output is handled:The
plan-nixderivation builds even ifcabal configurefails.When it fails, it copies
failed-cabal-configure.nixto the$out/default.nixalong with a copy of thecabal configureoutput.When
failed-cabal-configure.nixis imported and used in any way it writes thecabal configureoutput with__traceso it will always be visible.Instead of a
planthe imported nix contains aconfigurationErrorpointing thecabal configureoutput.The intermediate functions
configurationErrorand bubble it up to where it is needed.getPackagereturns a mostly empty proxy for a real package when there is aconfigurationErrorThe
getComponentfunction always returns a derivation, but the version in the proxy writes thecabal configureoutput to stdout and callsexit 1(so that it will never build).