feat: add detailed per-check inspection and styled reports

README.md

@@ -893,6 +893,10 @@ The most important differences:
 
 When tests fail, you get helpful output with file paths and violation details:
 
+Interactive terminals also highlight the failure summary, numbered headings,
+paths, metric values, and rule rationale. Output stays plain when redirected,
+when `CI=true`, or when `NO_COLOR` is set (even to an empty value).
+
 ```
 Found 2 architecture violation(s):
 
@@ -905,25 +909,91 @@ Found 2 architecture violation(s):
 
 ## 📝 Debug Logging & Configuration
 
-We support logging to help you understand what files are being analyzed and troubleshoot test failures. Logging is disabled by default to keep test output clean.
+Logging is disabled by default. Enable it per check to inspect file discovery,
+graph extraction and cache use, selector decisions, edge projections, class
+analysis, metric values, and the resulting violations. File, layer, slice,
+count/LCOM/distance, and custom metric checks use the same logging options.
+
+| Level | What you see |
+| --- | --- |
+| `error` | Analysis exceptions (the original exception is still raised). |
+| `warn` | Failed check summaries and every violation, plus errors. |
+| `info` | Check start, completion, duration, and violations, plus errors. |
+| `debug` | All of the above, plus rule configuration, discovered files, dependencies, cache decisions, selector matches, projected/omitted edges, classes, and measured values. |
 
 ### Enabling Debug Logging
 
 ```python
-from archunitpython import CheckOptions
-from archunitpython.common.logging.types import LoggingOptions
+from archunitpython import CheckOptions, LoggingOptions, project_files
+
+rule = project_files("src/").should().have_no_cycles()
 
 options = CheckOptions(
     logging=LoggingOptions(
         enabled=True,
         level="debug",       # "error" | "warn" | "info" | "debug"
-        log_file=True,       # Creates logs/archunit-YYYY-MM-DD_HH-MM-SS.log
+        log_file=True,       # Creates a unique timestamped file in logs/
     ),
 )
 
 violations = rule.check(options)
 ```
 
+For example, a debug trace includes entries like these (paths and timings depend
+on your project):
+
+```text
+[INFO] Starting check: CycleFreeFileCondition
+[DEBUG] Graph cache miss
+[DEBUG] Discovered file: /project/src/api.py
+[DEBUG] Processing file: /project/src/api.py
+[DEBUG] Dependency: /project/src/api.py -> /project/src/storage.py; external=False; kinds=[]
+[DEBUG] Projection: /project/src/api.py -> /project/src/storage.py becomes /project/src/api.py -> /project/src/storage.py
+[INFO] Finished check: CycleFreeFileCondition - 0 violation(s) (0.002s)
+```
+
+Console diagnostics use the standard `archunitpython` logger when handlers are
+configured, respecting their levels and formatting; otherwise they go to stderr.
+For pytest live logs, use `pytest --log-cli-level=DEBUG`. You can also configure
+Python's standard `logging` module in your application.
+
+### Save detailed inspection without console noise
+
+```python
+options = CheckOptions(logging=LoggingOptions(
+    enabled=True,
+    level="debug",
+    console=False,
+    log_file=True,
+    log_path="logs/architecture.log",
+    append_to_log_file=True,
+))
+violations = rule.check(options)
+```
+
+File logs are UTF-8, timestamped, and contain no added ANSI colors. Automatic
+paths are unique per check; an explicit `log_path` replaces that path.
+`append_to_log_file=False` overwrites an explicit file at the start of each check.
+Each check closes its own output file and isolates its diagnostics from nested
+and concurrent checks. Use separate paths when concurrent checks write to files.
+Diagnostic output is best effort: an unavailable file or failing logging handler
+does not change rule results or hide analysis exceptions. Debug inspection does
+not re-run custom predicates or metric calculations.
+
+### Format results independently of logging
+
+```python
+from archunitpython import assert_passes, format_violations
+
+print(format_violations(violations))               # Detect terminal colors
+text = format_violations(violations, color=False)  # Stable plain text for artifacts
+assert_passes(rule, options, color=False)         # Plain assertion failure
+```
+
+Pass `color=True` to explicitly request ANSI styling; `NO_COLOR` always wins.
+The numbered report, rationale, and details remain available at every log level,
+including when logging is disabled. Existing plain-text report wording is retained.
+
 ### CI Pipeline Integration
 
 ```yaml

src/archunitpython/__init__.py

@@ -7,6 +7,7 @@
 from archunitpython.common import (
     CheckOptions,
     EmptyTestViolation,
+    LoggingOptions,
     TechnicalError,
     UserError,
     Violation,
@@ -50,6 +51,7 @@
     "Violation",
     "EmptyTestViolation",
     "CheckOptions",
+    "LoggingOptions",
     "TechnicalError",
     "UserError",
     "extract_graph",

src/archunitpython/common/extraction/extract_graph.py

@@ -9,6 +9,7 @@
 
 from archunitpython.common.extraction.graph import Edge, Graph, ImportKind
 from archunitpython.common.fluentapi.checkable import CheckOptions
+from archunitpython.common.logging.inspection import debug, debug_enabled
 
 GraphCacheKey = tuple[str, tuple[str, ...], bool]
 
@@ -57,8 +58,7 @@ def matches(self, import_: _LocatedImport) -> bool:
         if not self.modules:
             return True
         return any(
-            import_.module_name == module
-            or import_.module_name.startswith(f"{module}.")
+            import_.module_name == module or import_.module_name.startswith(f"{module}.")
             for module in self.modules
         )
 
@@ -97,21 +97,46 @@ def extract_graph(
     ignore_type_checking_imports = bool(options and options.ignore_type_checking_imports)
     cache_key = _build_cache_key(project_path, excludes, ignore_type_checking_imports)
 
+    debug(
+        "Extraction root: %s; excludes: %s; ignore type-only imports: %s",
+        project_path,
+        excludes,
+        ignore_type_checking_imports,
+    )
     if options and options.clear_cache:
+        debug("Clearing graph cache for %s", project_path)
         _graph_cache.pop(cache_key, None)
 
     if cache_key in _graph_cache:
+        debug("Graph cache hit: %d edges", len(_graph_cache[cache_key]))
+        _inspect_graph(_graph_cache[cache_key])
         return _graph_cache[cache_key]
+    debug("Graph cache miss")
 
     result = _extract_graph_uncached(
         project_path,
         excludes,
         ignore_type_checking_imports=ignore_type_checking_imports,
     )
+    _inspect_graph(result)
     _graph_cache[cache_key] = result
     return result
 
 
+def _inspect_graph(graph: Graph) -> None:
+    if not debug_enabled():
+        return
+    debug("Extracted graph: %d edges (including self-edges)", len(graph))
+    for edge in graph:
+        debug(
+            "Dependency: %s -> %s; external=%s; kinds=%s",
+            edge.source,
+            edge.target,
+            edge.external,
+            edge.import_kinds,
+        )
+
+
 def _build_cache_key(
     project_path: str,
     exclude_patterns: list[str],
@@ -167,6 +192,7 @@ def _extract_graph_uncached(
     normalized_py_file_set = {_normalize(f) for f in py_files_set}
 
     for file_path in py_files:
+        debug("Processing file: %s", file_path)
         # Add self-referencing edge (ensures the file appears as a node)
         edges.append(
             Edge(
@@ -179,17 +205,21 @@ def _extract_graph_uncached(
         imports = _extract_located_imports(file_path)
         for located_import in imports:
             import_kind = located_import.import_kind
-            if (
-                ignore_type_checking_imports
-                and import_kind == ImportKind.TYPE_IMPORT
-            ):
+            if ignore_type_checking_imports and import_kind == ImportKind.TYPE_IMPORT:
+                debug(
+                    "Skipped type-only import: %s:%s -> %s",
+                    file_path,
+                    located_import.line_number,
+                    located_import.module_name,
+                )
                 continue
             for resolved, is_external in _resolve_import_targets(
                 located_import, file_path, project_path
             ):
                 if resolved and resolved != _normalize(file_path):
                     # Check if the resolved path is in our project
                     if not is_external and resolved not in normalized_py_file_set:
+                        debug("Skipped excluded dependency: %s -> %s", file_path, resolved)
                         continue
 
                     edges.append(
@@ -227,6 +257,7 @@ def _find_python_files(root: str, exclude: list[str]) -> list[str]:
                 full_path, root, exclude, is_dir=False
             ):
                 py_files.append(os.path.abspath(full_path))
+                debug("Discovered file: %s", full_path)
 
     return py_files
 
@@ -313,9 +344,7 @@ def _extract_located_imports(file_path: str) -> list[_LocatedImport]:
                 conditional_import_ranges,
             )
             for alias in node.names:
-                imports.append(
-                    _LocatedImport(alias.name, kind, node.lineno, syntax_kind)
-                )
+                imports.append(_LocatedImport(alias.name, kind, node.lineno, syntax_kind))
 
         elif isinstance(node, ast.ImportFrom):
             syntax_kind = (
@@ -329,9 +358,7 @@ def _extract_located_imports(file_path: str) -> list[_LocatedImport]:
                 type_checking_ranges,
                 conditional_import_ranges,
             )
-            fallback_module_name = (
-                "." * node.level if node.level and node.module is None else None
-            )
+            fallback_module_name = "." * node.level if node.level and node.module is None else None
             aliases = _module_aliases(node) if node.module else ()
             for module_name in _import_from_module_names(node):
                 imports.append(
@@ -354,15 +381,9 @@ def _extract_located_imports(file_path: str) -> list[_LocatedImport]:
                 conditional_import_ranges,
             )
             for module_name in _extract_dynamic_import_names(node):
-                imports.append(
-                    _LocatedImport(module_name, kind, node.lineno, syntax_kind)
-                )
+                imports.append(_LocatedImport(module_name, kind, node.lineno, syntax_kind))
 
-    return [
-        import_
-        for import_ in imports
-        if not _is_ignored_import(import_, ignore_directives)
-    ]
+    return [import_ for import_ in imports if not _is_ignored_import(import_, ignore_directives)]
 
 
 def _find_ignore_directives(source: str) -> dict[int, _IgnoreDirective]:
@@ -555,14 +576,10 @@ def _resolve_import(
     Returns (resolved_path, is_external).
     The path is normalized with forward slashes.
     """
-    if (
-        kind
-        in (
-            ImportKind.RELATIVE_IMPORT,
-            ImportKind.TYPE_IMPORT,
-        )
-        and import_name.startswith(".")
-    ):
+    if kind in (
+        ImportKind.RELATIVE_IMPORT,
+        ImportKind.TYPE_IMPORT,
+    ) and import_name.startswith("."):
         # Relative import
         return _resolve_relative_import(import_name, source_file, project_root)
 

src/archunitpython/common/fluentapi/inspection.py

@@ -0,0 +1,79 @@
+"""Observational instrumentation for the existing check contract."""
+
+from __future__ import annotations
+
+from functools import wraps
+from time import perf_counter
+from typing import Callable, TypeVar, cast
+
+from archunitpython.common.assertion.violation import Violation
+from archunitpython.common.fluentapi.checkable import CheckOptions
+from archunitpython.common.logging.inspection import InspectionSession, current_session
+
+F = TypeVar("F", bound=Callable[..., list[Violation]])
+
+
+def inspect_check(check: F) -> F:
+    """Trace a check while preserving its options, results, and exceptions."""
+
+    @wraps(check)
+    def inspected(self: object, options: CheckOptions | None = None) -> list[Violation]:
+        logging_options = options.logging if options else None
+        session = (
+            InspectionSession(logging_options)
+            if logging_options and logging_options.enabled
+            else None
+        )
+        token = current_session.set(session)
+        started = perf_counter() if session else 0.0
+        rule_name = type(self).__name__
+        try:
+            if session:
+                session.emit("info", "Starting check: %s", rule_name)
+                # Describe only known rule configuration, never user callbacks.
+                for name in (
+                    "_project_path",
+                    "_filters",
+                    "_subject_filters",
+                    "_object_filters",
+                    "_module_filters",
+                    "_pre_filters",
+                    "_check_filters",
+                    "_is_negated",
+                    "_pattern",
+                    "_regex",
+                    "_source",
+                    "_target",
+                    "_layers",
+                    "_allowed_dependencies",
+                    "_forbidden_dependencies",
+                    "_threshold",
+                    "_comparison",
+                    "_metric_attr",
+                    "_name",
+                    "_zone_type",
+                ):
+                    if session.options.level == "debug" and name in vars(self):
+                        session.emit("debug", "%s: %s", name.removeprefix("_"), vars(self)[name])
+            violations = check(self, options)
+            if session:
+                session.emit(
+                    "warn" if violations else "info",
+                    "Finished check: %s - %d violation(s) (%.3fs)",
+                    rule_name,
+                    len(violations),
+                    perf_counter() - started,
+                )
+                for violation in violations:
+                    session.emit("warn", "Violation: %s", violation)
+            return violations
+        except Exception as error:
+            if session:
+                session.emit("error", "Check failed: %s - %s", rule_name, error)
+            raise
+        finally:
+            current_session.reset(token)
+            if session:
+                session.close()
+
+    return cast(F, inspected)