makeWrapper: Don't readd existing values in prefix/suffix

When prefixing or suffixing list variables, check that the value or
values aren't already part of the list. If this is the case when
suffixing, the list won't be touched at all. When prefixing, however,
the last matching instance of the value will be moved to the beginning
of the list. Any remaining duplicates of the value will be left as-is.

Co-authored-by: Vincenzo Mantova <xworld21@users.sf.net>

pkgs/build-support/setup-hooks/make-wrapper.sh

@@ -36,6 +36,58 @@ makeWrapper() {
 
     assertExecutable "$original"
 
+    # Write wrapper code which adds `value` to the beginning or end of
+    # the list variable named by `varName`, depending on the `mode`
+    # specified.
+    #
+    # A value which is already part of the list will not be added
+    # again. If this is the case and the `suffix` mode is used, the
+    # list won't be touched at all. The `prefix` mode will however
+    # move the last matching instance of the value to the beginning
+    # of the list. Any remaining duplicates of the value will be left
+    # as-is.
+    addValue() {
+        local mode="$1"       # `prefix` or `suffix` to add to the beginning or end respectively
+        local varName="$2"    # name of list variable to add to
+        local separator="$3"  # character used to separate elements of list
+        local value="$4"      # one value, or multiple values separated by `separator`, to add to list
+        if test -n "$value"; then
+            local old_ifs=$IFS
+            IFS=$separator
+
+            if [[ "$mode" == '--prefix'* ]]; then
+                # Keep the order of the components as written when
+                # prefixing; normally, they would be added in the
+                # reverse order.
+                local tmp=
+                for v in $value; do
+                    tmp=$v${tmp:+$separator}$tmp
+                done
+                value="$tmp"
+            fi
+            for v in $value; do
+                {
+                    echo "$varName=\${$varName:+${separator@Q}\$$varName${separator@Q}}"               # add separators on both ends unless empty
+                    if [[ "$mode" == '--prefix'* ]]; then                                              # -- in prefix mode --
+                        echo "$varName=\${$varName/${separator@Q}${v@Q}${separator@Q}/${separator@Q}}" # remove the first instance of the value (if any)
+                        echo "$varName=${v@Q}\$$varName"                                               # prepend the value
+                    elif [[ "$mode" == '--suffix'* ]]; then                                            # -- in suffix mode --
+                        echo "if [[ \$$varName != *${separator@Q}${v@Q}${separator@Q}* ]]; then"       # if the value isn't already in the list
+                        echo "    $varName=\$$varName${v@Q}"                                           # append the value
+                        echo "fi"
+                    else
+                        echo "unknown mode $mode!" 1>&2
+                        exit 1
+                    fi
+                    echo "$varName=\${$varName#${separator@Q}}"                                        # remove leading separator
+                    echo "$varName=\${$varName%${separator@Q}}"                                        # remove trailing separator
+                    echo "export $varName"
+                } >> "$wrapper"
+            done
+            IFS=$old_ifs
+        fi
+    }
+
     mkdir -p "$(dirname "$wrapper")"
 
     echo "#! @shell@ -e" > "$wrapper"
@@ -67,28 +119,14 @@ makeWrapper() {
             separator="${params[$((n + 2))]}"
             value="${params[$((n + 3))]}"
             n=$((n + 3))
-            if test -n "$value"; then
-                if test "$p" = "--suffix"; then
-                    echo "export $varName=\$$varName\${$varName:+${separator@Q}}${value@Q}" >> "$wrapper"
-                else
-                    echo "export $varName=${value@Q}\${$varName:+${separator@Q}}\$$varName" >> "$wrapper"
-                fi
-            fi
-        elif [[ "$p" == "--prefix-each" ]]; then
-            varName="${params[$((n + 1))]}"
-            separator="${params[$((n + 2))]}"
-            values="${params[$((n + 3))]}"
-            n=$((n + 3))
-            for value in $values; do
-                echo "export $varName=${value@Q}\${$varName:+${separator@Q}}\$$varName" >> "$wrapper"
-            done
-        elif [[ "$p" == "--suffix-each" ]]; then
+            addValue "$p" "$varName" "$separator" "$value"
+        elif [[ ("$p" == "--suffix-each") || ("$p" == "--prefix-each") ]]; then
             varName="${params[$((n + 1))]}"
             separator="${params[$((n + 2))]}"
             values="${params[$((n + 3))]}"
             n=$((n + 3))
             for value in $values; do
-                echo "export $varName=\$$varName\${$varName:+$separator}${value@Q}" >> "$wrapper"
+                addValue "$p" "$varName" "$separator" "$value"
             done
         elif [[ ("$p" == "--suffix-contents") || ("$p" == "--prefix-contents") ]]; then
             varName="${params[$((n + 1))]}"
@@ -97,11 +135,7 @@ makeWrapper() {
             n=$((n + 3))
             for fileName in $fileNames; do
                 contents="$(cat "$fileName")"
-                if test "$p" = "--suffix-contents"; then
-                    echo "export $varName=\$$varName\${$varName:+$separator}${contents@Q}" >> "$wrapper"
-                else
-                    echo "export $varName=${contents@Q}\${$varName:+$separator}\$$varName" >> "$wrapper"
-                fi
+                addValue "$p" "$varName" "$separator" "$contents"
             done
         elif [[ "$p" == "--add-flags" ]]; then
             flags="${params[$((n + 1))]}"