feat: add shared grammar terminals for systemd integer and route-table parsing

src/main/kotlin/net/sjrx/intellij/plugins/systemdunitfiles/semanticdata/optionvalues/grammar/Coloring.kt

@@ -37,6 +37,7 @@ data class Region(val start: Int, val end: Int, val role: Role, val tag: Semanti
 fun defaultRole(terminal: TerminalCombinator): Role? = when (terminal) {
   is IntegerTerminal -> Role.LITERAL
   is UnsignedNumberTerminal -> Role.LITERAL
+  is SafeAtoTerminal -> Role.LITERAL
   is ByteSizeTerminal -> Role.LITERAL
   is LiteralChoiceTerminal -> if (terminal.choices.allPunctuation()) Role.OPERATOR else Role.ENUM
   is FlexibleLiteralChoiceTerminal -> if (terminal.choices.allPunctuation()) Role.OPERATOR else Role.ENUM

src/main/kotlin/net/sjrx/intellij/plugins/systemdunitfiles/semanticdata/optionvalues/grammar/RouteTable.kt

@@ -0,0 +1,70 @@
+package net.sjrx.intellij.plugins.systemdunitfiles.semanticdata.optionvalues.grammar
+
+/*
+ * Route tables as systemd-networkd reads them, pinned to systemd 0f0682b773 (the plugin's last_commit_hash).
+ *
+ * Every route-table setting hands its whole (stripped) value to manager_get_route_table_from_string():
+ * [Route] Table=, [RoutingPolicyRule] Table=, [VRF] Table=, [WireGuard] RouteTable=, [WireGuardPeer] RouteTable=,
+ * and RouteTable= in [DHCPv4], [DHCPv6] and [IPv6AcceptRA]. That function tries, in order
+ * (https://github.com/systemd/systemd/blob/0f0682b773/src/network/networkd-route-util.c#L435-L464):
+ *
+ *  1. the predefined names `default`, `main`, `local`, compared case-sensitively
+ *     (https://github.com/systemd/systemd/blob/0f0682b773/src/network/networkd-route-util.c#L427-L433);
+ *  2. the names an administrator defined with RouteTable=NAME:NUMBER in networkd.conf;
+ *  3. safe_atou32() on the whole value, refusing 0 with -ERANGE.
+ *
+ * THE LENIENCY. Step 2 depends on networkd.conf, which the plugin cannot see, so any value that could be such a
+ * name is accepted. config_parse_route_table_names() decides what a name may be
+ * (https://github.com/systemd/systemd/blob/0f0682b773/src/network/networkd-route-util.c#L496-L616):
+ *  - each word comes from extract_first_word(…, NULL, 0) (#L526). With flags 0 a backslash takes the next
+ *    character literally: https://github.com/systemd/systemd/blob/0f0682b773/src/basic/extract-word.c#L142-L144
+ *    sets the flag and https://github.com/systemd/systemd/blob/0f0682b773/src/basic/extract-word.c#L105-L106 copies
+ *    the character. So `my\ table:100` defines the name `my table`, and a name may contain whitespace;
+ *  - the name is the part before the first `:` (#L537-L544), so it never contains `:`;
+ *  - it must not be empty (#L546-L550) or consist only of the digits 0-9 (#L551-L555);
+ *  - it must not be a predefined name (#L556-L561), but those are accepted by step 1 anyway.
+ * So every non-empty value without a `:` that is not all digits is a possible name. That includes spellings that
+ * look numeric but are not all digits, such as `0x0`, `-0`, `+5` and `0b 1`, and capitalised forms such as `Main`.
+ * Without a matching networkd.conf entry systemd rejects most of these (sd-check, which loads no networkd.conf,
+ * reports `Table=0x0`, `Table=-0` and `Table=mytable`). Flagging "a name that is not defined anywhere we can see"
+ * would be stricter than the parser and belongs in a separate, weaker inspection.
+ *
+ * What is flagged, as systemd does whatever networkd.conf says: a value containing `:`, and an all-digit value that
+ * safe_atou32 refuses (`0`, `00`, `08`, `4294967296`, `040000000000`). All of these were confirmed with sd-check on
+ * [Route] Table=, [RoutingPolicyRule] Table=, [DHCPv4] RouteTable= and [VRF] Table=.
+ *
+ * Settings that check something else first must add that branch themselves. The WireGuard keys, for example, take
+ * an empty value or a false boolean to mean "off" before they look up a table (netdev/wireguard.c).
+ */
+
+/** The predefined table names (route_table_table), case-sensitive. */
+val ROUTE_TABLE_PREDEFINED_NAME = LiteralChoiceTerminal("default", "main", "local")
+
+/** A table number: safe_atou32() on the whole value, with 0 refused by manager_get_route_table_from_string(). */
+val ROUTE_TABLE_NUMBER = SafeAtoTerminal(
+  signed = false,
+  base = 0,
+  flags = emptySet(),
+  minInclusive = 1L,
+  maxInclusive = 4_294_967_295L,
+  acceptsWhitespace = true,
+  acceptsMinus = true,
+)
+
+/**
+ * A word that networkd.conf's RouteTable= could have defined as a table name. It is non-empty, has no `:`, and is
+ * not made up only of digits (see the file comment for the C rules). The shape is exact, so an all-digit value is
+ * left to [ROUTE_TABLE_NUMBER] and its errors are located the way safe_atou32 would locate them.
+ */
+val ROUTE_TABLE_USER_DEFINED_NAME = RegexTerminal("""(?![0-9]+(?::|\z))[^:]+""", """(?![0-9]+(?::|\z))[^:]+""")
+
+/**
+ * A complete route-table value, as manager_get_route_table_from_string() reads it. This includes the end of input,
+ * so use it as the whole grammar of the value or as one alternative of it. Each branch carries its own [EOF], so
+ * the classic first-match engine can still fall back from the number branch to the name branch on `1abc`.
+ */
+val ROUTE_TABLE_FROM_STRING = AlternativeCombinator(
+  SequenceCombinator(ROUTE_TABLE_PREDEFINED_NAME, EOF()),
+  SequenceCombinator(ROUTE_TABLE_NUMBER, EOF()),
+  SequenceCombinator(ROUTE_TABLE_USER_DEFINED_NAME, EOF()),
+)