Rework libarrow activate.sh with finer-grained checks and logging (co…

…nda-forge#1065)

recipe/activate.sh

@@ -7,33 +7,70 @@
 # doesn't come with a deactivate script, because the symlink
 # is benign and doesn't need to be deleted.
 
+_la_log() {
+    if [ "$CF_LIBARROW_ACTIVATE_LOGGING" = "1" ]; then
+        # The following loop is necessary to handle multi-line strings
+        # like for the output of `ls -al`.
+        printf '%s\n' "$*" | while IFS= read -r line
+        do
+            echo "$CONDA_PREFIX/etc/conda/activate.d/libarrow_activate.sh DEBUG: $line"
+        done
+    fi
+}
+
+_la_log "Beginning libarrow activation."
+
 # where the GDB wrappers get installed
-GDB_PREFIX="$CONDA_PREFIX/share/gdb/auto-load"
+_la_gdb_prefix="$CONDA_PREFIX/share/gdb/auto-load"
 
 # this needs to be in sync with the respective patch
-PLACEHOLDER="replace_this_section_with_absolute_slashed_path_to_CONDA_PREFIX"
+_la_placeholder="replace_this_section_with_absolute_slashed_path_to_CONDA_PREFIX"
 # the paths here are intentionally stacked, see #935, resp.
 # https://github.com/apache/arrow/blob/master/docs/source/cpp/gdb.rst#manual-loading
-WRAPPER_DIR="$GDB_PREFIX/$CONDA_PREFIX/lib"
+_la_symlink_dir="$_la_gdb_prefix/$CONDA_PREFIX/lib"
+_la_orig_install_dir="$_la_gdb_prefix/$_la_placeholder/lib"
 
-mkdir -p "$WRAPPER_DIR" || true
-# If the directory is not writable, nothing can be done
-if [ ! -w "$WRAPPER_DIR" ]; then
-    return
-fi
+_la_log "          _la_gdb_prefix: $_la_gdb_prefix"
+_la_log "         _la_placeholder: $_la_placeholder"
+_la_log "         _la_symlink_dir: $_la_symlink_dir"
+_la_log "    _la_orig_install_dir: $_la_orig_install_dir"
+_la_log "  content of that folder:"
+_la_log "$(ls -al "$_la_orig_install_dir" | sed 's/^/      /')"
 
-# there's only one lib in that folder, but the libname changes
+# there's only one lib in the _la_orig_install_dir folder, but the libname changes
 # based on the version so use a loop instead of hardcoding it.
-for f in "$GDB_PREFIX/$PLACEHOLDER/lib/"*.py; do
-    if [ ! -e "$f" ]; then
+for _la_target in "$_la_orig_install_dir/"*.py; do
+    if [ ! -e "$_la_target" ]; then
         # If the file doesn't exist, skip this iteration of the loop.
         # (This happens when no files are found, in which case the
-        # loop runs with f equal to the pattern itself.)
+        # loop runs with target equal to the pattern itself.)
+        _la_log 'Folder $_la_orig_install_dir seems to not contain .py files, skipping'
+        continue
+    fi
+    _la_symlink="$_la_symlink_dir/$(basename "$_la_target")"
+    _la_log "   _la_target: $_la_target"
+    _la_log "  _la_symlink: $_la_symlink"
+    if [ -L "$_la_symlink" ] && [ "$(readlink "$_la_symlink")" = "$_la_target" ]; then
+        _la_log 'symlink $_la_symlink already exists and points to $_la_target, skipping.'
+        continue
+    fi
+    _la_log 'Creating symlink $_la_symlink pointing to $_la_target'
+    mkdir -p "$_la_symlink_dir" || true
+    # this check also creates the symlink; if it fails, we enter the if-branch.
+    if ! ln -sf "$_la_target" "$_la_symlink"; then
+        echo -n "${BASH_SOURCE[0]} ERROR: Failed to create symlink from "
+        echo -n "'$_la_target' to '$_la_symlink'"
+        echo
         continue
     fi
-    target="$WRAPPER_DIR/$(basename "$f")"
-    # We have write permissions to WRAPPER_DIR but not necessarily target.
-    # Thus it's safest to delete the target in case it already exists.
-    rm -f "$target"
-    ln -s "$f" "$WRAPPER_DIR/$(basename "$f")"
 done
+
+_la_log "Libarrow activation complete."
+
+unset _la_gdb_prefix
+unset _la_log
+unset _la_orig_install_dir
+unset _la_placeholder
+unset _la_symlink
+unset _la_symlink_dir
+unset _la_target