Avoid use of parseIndexState (#1903)

* Avoid use of `parseIndexState`

The `parseIndexState` uses a very simple parser that breaks for `cabal.project` files with more complicated `index-state:` fields.

This will have some drawbacks:

* There will no longer be a warning in the trace output if an index state was not found.

* When `hackage.nix` is bumped the plan will be recomputed even if the `index-state:` in the `cabal.project` has not changed. We do not expect this to be a problem since recomputing the plan is normally relatively fast.

* Update change log

Author: hamishmack

changelog.md

@@ -1,6 +1,28 @@
 This file contains a summary of changes to Haskell.nix and `nix-tools`
 that will impact users.
 
+## Mar 27, 2023
+
+Haskell.nix will no longer parse the `cabal.project` file to
+determine the `index-state`. This decision was made due to
+the function's inability to handle more than one `index-state`
+or a qualified `index-state` as the first `index-state`
+field in the file.
+
+As a result, there will be some drawbacks:
+
+* There will no longer be a warning in the trace output
+  if an index state is not found.
+
+* Even if the `index-state:` in the `cabal.project` has not changed,
+  the plan will be recomputed when hackage.nix is bumped. However, this
+  is not expected to be a problem since plan recomputations are typically
+  quick.
+
+* `project.index-state` cannot be used to obtain the found `index-state`.
+  However, the parse function is still available if required
+  (haskell-nix.haskellLib.parseIndexState).  
+
 ## Jul 27, 2022
 * Removed reliance on `builtins.currentSystem`.  It was used it to provide
   `pkgs.evalPackages` via an overlay that it used to run derivations

lib/call-cabal-project-to-nix.nix

@@ -151,46 +151,29 @@ in let
     }
   '';
 
-  cabalProjectIndexState = pkgs.haskell-nix.haskellLib.parseIndexState rawCabalProject;
-
-  index-state-found =
+  index-state-max =
     if index-state != null
     then index-state
-    else if cabalProjectIndexState != null
-    then cabalProjectIndexState
-    else
-      let latest-index-state = pkgs.lib.last (builtins.attrNames index-state-hashes);
-      in builtins.trace ("No index state specified" + (if name == null then "" else " for " + name) + ", using the latest index state that we know about (${latest-index-state})!") latest-index-state;
-
-  index-state-pinned = index-state != null || cabalProjectIndexState != null;
+    else pkgs.lib.last (builtins.attrNames index-state-hashes);
 
   pkgconfPkgs = import ./pkgconf-nixpkgs-map.nix pkgs;
 
-in
-  assert (if index-state-found == null
-    then throw "No index state passed and none found in ${cabalProjectFileName}" else true);
-
-  assert (if index-sha256 == null && !(pkgs.lib.hasSuffix "Z" index-state-found)
-    then throw "Index state found was ${index-state-found} and no `index-sha256` was provided. "
-      "The index hash lookup code requires zulu time zone (ends in a Z)" else true);
-
-let
   # If a hash was not specified find a suitable cached index state to
   # use that will contain all the packages we need.  By using the
   # first one after the desired index-state we can avoid recalculating
   # when new index-state-hashes are added.
   # See https://github.com/input-output-hk/haskell.nix/issues/672
   cached-index-state = if index-sha256 != null
-    then index-state-found
+    then index-state-max
     else
       let
         suitable-index-states =
           builtins.filter
-            (s: s >= index-state-found) # This compare is why we need zulu time
+            (s: s >= index-state-max) # This compare is why we need zulu time
             (builtins.attrNames index-state-hashes);
       in
         if builtins.length suitable-index-states == 0
-          then index-state-found
+          then index-state-max
           else pkgs.lib.head suitable-index-states;
 
   # Lookup hash for the index state we found
@@ -200,7 +183,7 @@ let
 
 in
   assert (if index-sha256-found == null
-    then throw "Unknown index-state ${index-state-found}, the latest index-state I know about is ${pkgs.lib.last (builtins.attrNames index-state-hashes)}. You may need to update to a newer hackage.nix." else true);
+    then throw "Unknown index-state ${index-state-max}, the latest index-state I know about is ${pkgs.lib.last (builtins.attrNames index-state-hashes)}. You may need to update to a newer hackage.nix." else true);
 
 let
   # Deal with source-repository-packages in a way that will work in
@@ -392,11 +375,6 @@ let
     sha256 = plan-sha256;
     sha256Arg = "plan-sha256";
     this = "project.plan-nix" + (if name != null then " for ${name}" else "");
-    # Before pinning stuff down we need an index state to use
-    reasonNotSafe =
-      if !index-state-pinned
-        then "index-state is not pinned by an argument or the cabal project file"
-        else null;
   } // pkgs.lib.optionalAttrs (checkMaterialization != null) {
     inherit checkMaterialization;
   }) (evalPackages.runCommand (nameAndSuffix "plan-to-nix-pkgs") {
@@ -470,12 +448,11 @@ let
     export SSL_CERT_FILE=${cacert}/etc/ssl/certs/ca-bundle.crt
     export GIT_SSL_CAINFO=${cacert}/etc/ssl/certs/ca-bundle.crt
 
-    echo "Using index-state ${index-state-found}"
     CABAL_DIR=${
       # This creates `.cabal` directory that is as it would have
       # been at the time `cached-index-state`.  We may include
-      # some packages that will be excluded by `index-state-found`
-      # which is used by cabal (cached-index-state >= index-state-found).
+      # some packages that will be excluded by `index-state-max`
+      # which is used by cabal (cached-index-state >= index-state-max).
       dotCabal {
         inherit cabal-install nix-tools extra-hackage-tarballs;
         extra-hackage-repos = fixedProject.repos;
@@ -485,7 +462,7 @@ let
     } make-install-plan ${
           # Setting the desired `index-state` here in case it is not
           # in the cabal.project file. This will further restrict the
-          # packages used by the solver (cached-index-state >= index-state-found).
+          # packages used by the solver (cached-index-state >= index-state-max).
           pkgs.lib.optionalString (index-state != null) "--index-state=${index-state}"
         } \
         -w ${
@@ -548,7 +525,6 @@ let
   '');
 in {
   projectNix = plan-nix;
-  index-state = index-state-found;
-  inherit src;
+  inherit index-state-max src;
   inherit (fixedProject) sourceRepos extra-hackages;
 }