Hermes-agent

agent/lsp/range_shift.py

@@ -0,0 +1,149 @@
+"""Diff-aware line-shift map for cross-edit LSP delta filtering.
+
+When an edit deletes or inserts lines in the middle of a file, every
+diagnostic below the edit point shifts to a new line number.  The
+LSPService delta filter subtracts the pre-edit baseline from the
+post-edit diagnostics keyed on ``(severity, code, source, message,
+range)`` — without an adjustment, the shifted-but-otherwise-identical
+diagnostics look brand-new and the agent gets flooded with noise.
+
+The fix used here is the same trick git's blame and unified diff use:
+build a piecewise-linear map from pre-edit line numbers to post-edit
+line numbers, then apply that map to baseline diagnostics before the
+set-difference.  Diagnostics whose pre-edit line is in a region the
+edit deleted return ``None`` and are dropped from the baseline (they
+genuinely no longer apply).
+
+Trade-off vs. dropping range from the key entirely (the previous
+fix): preserves the "new instance of an identical error at a
+different line" signal — if the model introduces a second instance
+of the same error class at a different location, that one will be
+surfaced as new instead of swallowed by content-only dedup.
+
+The map is derived from ``difflib.SequenceMatcher.get_opcodes()`` and
+exposed as a single callable so callers don't have to reason about
+diff regions.
+"""
+from __future__ import annotations
+
+import difflib
+from typing import Any, Callable, Dict, List, Optional
+
+
+def build_line_shift(pre_text: str, post_text: str) -> Callable[[int], Optional[int]]:
+    """Build a function mapping pre-edit line numbers to post-edit line numbers.
+
+    Lines are 0-indexed to match the LSP wire format
+    (``range.start.line`` is 0-indexed).
+
+    The returned callable takes a pre-edit 0-indexed line number and
+    returns the corresponding post-edit 0-indexed line number, or
+    ``None`` if that line was deleted by the edit (no post-edit
+    counterpart exists).
+
+    Cost: one ``SequenceMatcher.get_opcodes()`` call up front; the
+    returned closure is O(log n) per call (binary search over opcode
+    regions).  Cheap enough to call once per write/patch and apply to
+    every baseline diagnostic.
+    """
+    pre_lines = pre_text.splitlines() if pre_text else []
+    post_lines = post_text.splitlines() if post_text else []
+
+    # Trivial case: identical content or no content — identity map.
+    if pre_lines == post_lines:
+        return lambda line: line
+
+    # SequenceMatcher.get_opcodes() returns a list of
+    # (tag, i1, i2, j1, j2) where tag is 'equal', 'replace', 'delete',
+    # or 'insert'.  i1:i2 is the range in pre, j1:j2 is the range in
+    # post.  We build a list of (i1, i2, j1, j2, tag) tuples and
+    # binary-search by i for each lookup.
+    sm = difflib.SequenceMatcher(a=pre_lines, b=post_lines, autojunk=False)
+    opcodes = sm.get_opcodes()
+
+    def shift(line: int) -> Optional[int]:
+        # Find the opcode region whose i1 <= line < i2.
+        # Linear scan is fine — typical opcode count is small (single
+        # digits for a typical patch-tool edit).
+        for tag, i1, i2, j1, j2 in opcodes:
+            if i1 <= line < i2:
+                if tag == "equal":
+                    # Pre-line N → post-line (N - i1 + j1).
+                    return line - i1 + j1
+                if tag == "delete":
+                    # Pre-line is in a deleted region — no post counterpart.
+                    return None
+                if tag == "replace":
+                    # Replace == delete + insert; the pre-line has no
+                    # post counterpart in any meaningful sense.  Drop.
+                    return None
+                # 'insert' has i1 == i2 so line < i2 can't be hit.
+            if line < i1:
+                # Past the relevant region — handled in earlier iteration.
+                break
+        # Past the last opcode region (line >= len(pre_lines)).
+        # Anchor at end of post.
+        return max(0, len(post_lines) - 1) if post_lines else None
+
+    return shift
+
+
+def shift_diagnostic_range(diag: Dict[str, Any],
+                           shift: Callable[[int], Optional[int]]) -> Optional[Dict[str, Any]]:
+    """Return a copy of ``diag`` with its line range remapped through ``shift``.
+
+    Returns ``None`` if the diagnostic's start line maps to ``None``
+    (the line was deleted by the edit) — caller drops it from the
+    baseline since the diagnostic no longer applies.
+
+    Both ``start.line`` and ``end.line`` are remapped independently;
+    when only the end maps to ``None`` (rare, multi-line diagnostic
+    straddling the edit boundary) we collapse to a single-line range
+    at the shifted start to keep the diagnostic in the baseline.
+
+    The original ``diag`` is not mutated.
+    """
+    rng = diag.get("range") or {}
+    start = rng.get("start") or {}
+    end = rng.get("end") or {}
+
+    pre_start_line = int(start.get("line", 0))
+    pre_end_line = int(end.get("line", pre_start_line))
+
+    new_start_line = shift(pre_start_line)
+    if new_start_line is None:
+        return None
+
+    new_end_line = shift(pre_end_line)
+    if new_end_line is None:
+        # Diagnostic straddled the deletion — collapse to start.
+        new_end_line = new_start_line
+
+    shifted = dict(diag)
+    shifted["range"] = {
+        "start": {
+            "line": new_start_line,
+            "character": int(start.get("character", 0)),
+        },
+        "end": {
+            "line": new_end_line,
+            "character": int(end.get("character", 0)),
+        },
+    }
+    return shifted
+
+
+def shift_baseline(baseline: List[Dict[str, Any]],
+                   shift: Callable[[int], Optional[int]]) -> List[Dict[str, Any]]:
+    """Apply ``shift`` to every diagnostic in ``baseline``, dropping deleted entries."""
+    out: List[Dict[str, Any]] = []
+    for d in baseline:
+        if not isinstance(d, dict):
+            continue
+        shifted = shift_diagnostic_range(d, shift)
+        if shifted is not None:
+            out.append(shifted)
+    return out
+
+
+__all__ = ["build_line_shift", "shift_diagnostic_range", "shift_baseline"]