Package dev.frostlake.executor.expressions

Class ExpressionSource

java.lang.Object
dev.frostlake.executor.expressions.ExpressionSource
public final class ExpressionSource extends Object
Where the expression currently being evaluated started inside its statement — the missing half of a reported position.

Operators are handed expressions as extracted TEXT, so by the time one is parsed nothing in the AST knows where that text came from. SourcePosition therefore records only a fragment-relative place (which keeps the by-text AST cache correct), and this class supplies the origin to add back: the statement line the fragment starts on, and the column it starts at.

Scoped to the thread, like the statement clock, because a session's statements run on the caller's thread. An expression evaluated with no origin set — a synthesised one, say, such as the t.a that star-expansion invents and that never appeared in the source — reports no position at all, which is the honest answer for text the user never wrote.

  • Method Details

    • begin

      public static SourcePosition begin(SourcePosition origin)
      Note where the fragment about to be evaluated begins, returning whatever origin it displaced so a nested evaluation can put it back.

    • beginNested

      public static SourcePosition beginNested(SourcePosition within)
      Note a fragment that lives INSIDE the fragment already in force, composing the two origins.

      Needed wherever a body is re-parsed from its own text and then walked item by item: a view's definition sits at some offset in the CREATE statement, and each select item sits at some offset in that definition, so a node's place in the STATEMENT is the two composed. begin(dev.frostlake.executor.expressions.SourcePosition) replaces the origin outright, which is right for one level and silently wrong for two — the inner origin would win and the body's own offset would vanish.

      Composition is resolve(dev.frostlake.executor.expressions.SourcePosition)'s arithmetic applied to the origin itself, so the line/column rule is stated in exactly one place: a fragment starting on the outer fragment's FIRST line is displaced by its column, one starting later keeps its own.

      Parameters:
      within - where the inner fragment begins, relative to the fragment currently in force
      Returns:
      whatever origin it displaced, for end(dev.frostlake.executor.expressions.SourcePosition)

    • end

      public static void end(SourcePosition previous)
      Put back whatever begin(dev.frostlake.executor.expressions.SourcePosition) displaced; null clears.

    • resolve

      public static SourcePosition resolve(SourcePosition withinFragment)
      The statement-relative place of a fragment-relative one, or null when no origin is set.

      A node on the fragment's FIRST line is offset by the origin's column; a node on a later line keeps its own column, because the origin's column only displaces the line it starts on.

    • hasOrigin

      public static boolean hasOrigin()
      Whether an origin is set — for callers that only build a message when one can be positioned.