dev-env: Add a symlink, dev-env/jdk, to the current JDK. (#7745)

* dev-env: Add a symlink, `dev-env/jdk`, to the current JDK.

This makes configuring IntelliJ IDEA to use the correct JDK much easier.

CHANGELOG_BEGIN
CHANGELOG_END

* dev-env: Document setting up the JDK in IntelliJ IDEA.

.gitignore

@@ -12,6 +12,7 @@ target
 .daml/
 
 # dev-env
+/dev-env/jdk
 /dev-env/var/
 
 # Bazel

BAZEL.md

@@ -244,7 +244,7 @@ file whenever you like, so don't worry too much.
 The first import of the project might fail due to a resolution error of the 
 `bazel` binary. In order to solve this, configure the Bazel plugin settings
 with the location of the `bazel` binary, 
-by setting _Preferences_ -> _Bazel Settings_ -> _Bazel binary location_ 
+by setting _Preferences_ → _Bazel Settings_ → _Bazel binary location_ 
 to `./dev-env/bin/bazel`.
 
 Now, re-trigger a sync of the workspace (IntelliJ Action: 
@@ -252,6 +252,22 @@ _Sync project with BUILD files_). This process will take a while.
 
 [intellij_project_view]: https://ij.bazel.build/docs/project-views.html
 
+### Configuring the JDK in IntelliJ
+
+DAML downloads the version of the JDK it uses from Nix. A symlink will be
+created by the dev-env utilities (make sure you've set these up) in
+_dev-env/jdk_.
+
+TO configure IntelliJ to use this JDK:
+
+1. Open the _Project Structure_ window.
+2. Under _Platform Settings_, select _SDKs_.
+3. Press the _plus_ button and select "Add JDK".
+4. Choose the _dev-env/jdk_ directory.
+5. Name it "DAML JDK" or something similar.
+6. Open _Project Settings_ →  _Project_.
+7. Select the DAML JDK from the _Project SDK_ list.
+
 ### Overview over Bazel IntelliJ Integration
 
 The IntelliJ interface should largely look the same as under SBT. However, the

dev-env/bin/dade-assist

@@ -2,4 +2,7 @@
 
 DADE_CURRENT_SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 source "$DADE_CURRENT_SCRIPT_DIR/../lib/dade-common"
+
+linkTool java out "${DADE_DEVENV_DIR}/jdk"
+
 exec "${DADE_DEVENV_DIR}/lib/dade-dump-profile"

dev-env/lib/dade-common

@@ -85,12 +85,20 @@ dadeGetOutput() {
 #     relalized into. This is necessary, since Nix's --add-root produces a
 #     unpredictable symlink name.
 #   force: if set to 1, forces re-initialization of the tool.
+#   target: the output location (defaults to "$DADE_GC_ROOTS/$attribute").
 buildTool() {
-  local attr=$1
+  local attribute=$1
   local outputName=$2
   local force=$3
   shift 3
-  local target="$DADE_GC_ROOTS/$attr"
+  if [[ $# -gt 0 ]]; then
+      local target=$1
+      local customTarget=1
+      shift 1
+  else
+      local target="$DADE_GC_ROOTS/$attribute"
+      local customTarget=0
+  fi
   local hashfile="${target}.hash"
   local hash="nope"
   local currentHash="$(dadeBaseHash)"
@@ -105,30 +113,41 @@ buildTool() {
   if [[ ! -e "$DADE_BUILD_RESULT" || "$force" -eq 1 || "$hash" != "$currentHash" ]]; then
     set -e
     test "$force" -eq 1 && forced=" (forced)"
-    errcho "Building tools.${attr}${forced}..."
+    errcho "Building tools.${attribute}${forced}..."
     # Allow to fail, so we can capture outpath and to capture the exit code too.
     set +e
-    outpath=$(nix-build "${DADE_BASE_ROOT}/nix/default.nix" -A tools.$attr -Q -o "${target}")
+    outpath=$(nix-build "${DADE_BASE_ROOT}/nix/default.nix" -A "tools.${attribute}" -Q -o "${target}")
     local dade_build_exit_code=$?
     set -e
     if [[ "$dade_build_exit_code" != "0" ]]; then
-      errcho "Build of tools.$attr has failed!"
+      errcho "Build of tools.$attribute has failed!"
       exit 1
     fi
-    errcho "Built tools.$attr in $outpath and linked to $DADE_BUILD_RESULT"
-    printf "$currentHash" >| "$hashfile"
+    errcho "Built tools.$attribute in $outpath and linked to $DADE_BUILD_RESULT"
+    if [[ $customTarget -eq 0 ]]; then
+        printf "$currentHash" >| "$hashfile"
+    fi
     set +e
   fi
 }
 
 # execTool <attribute> <outputName> <binary>
 execTool() {
-  local attr=$1
+  local attribute=$1
   local outputName=$2
   local binary=$3
   shift 3
   [[ $PATH =~ (^|.*:)$DADE_DEVENV_DIR/bin($|:.*) ]] || \
     eval "$(${DADE_DEVENV_DIR}/bin/dade assist)"
-  buildTool $attr $outputName 0
+  buildTool $attribute $outputName 0
   exec "$(readlink "$DADE_BUILD_RESULT")/bin/$binary" "$@"
 }
+
+# linkTool <attribute> <outputName> <target>
+linkTool() {
+  local attribute=$1
+  local outputName=$2
+  local target=$3
+  shift 3
+  buildTool $attribute $outputName 1 $target
+}