Improved error handling of long paths for EXE installers

CONSTRUCT.md

@@ -552,11 +552,11 @@ interactive installation. (Windows only).
 
 Only applies if `register_python` is true.
 
-### `check_path_length`
+### ~~`check_path_length`~~
 
-Check the length of the path where the distribution is installed to ensure nodejs
-can be installed.  Raise a message to request shorter paths (less than 46 character)
-or enable long paths on windows > 10 (require admin right). Default is False. (Windows only).
+_Deprecated_. Path length validation is now always performed using the computed
+maximum relative path length from the package contents. This option will be
+removed in a future version. (Windows only).
 
 ### `check_path_spaces`
 

constructor/_schema.py

@@ -721,11 +721,11 @@ class ConstructorConfiguration(BaseModel):
 
     Only applies if `register_python` is true.
     """
-    check_path_length: bool = False
+    check_path_length: bool = Field(False, deprecated=True)
     """
-    Check the length of the path where the distribution is installed to ensure nodejs
-    can be installed.  Raise a message to request shorter paths (less than 46 character)
-    or enable long paths on windows > 10 (require admin right). Default is False. (Windows only).
+    _Deprecated_. Path length validation is now always performed using the computed
+    maximum relative path length from the package contents. This option will be
+    removed in a future version. (Windows only).
     """
     check_path_spaces: bool = True
     """

constructor/data/construct.schema.json

@@ -477,7 +477,8 @@
     },
     "check_path_length": {
       "default": false,
-      "description": "Check the length of the path where the distribution is installed to ensure nodejs can be installed. Raise a message to request shorter paths (less than 46 character) or enable long paths on windows > 10 (require admin right). Default is False. (Windows only).",
+      "deprecated": true,
+      "description": "_Deprecated_. Path length validation is now always performed using the computed maximum relative path length from the package contents. This option will be removed in a future version. (Windows only).",
       "title": "Check Path Length",
       "type": "boolean"
     },

constructor/fcp.py

@@ -13,10 +13,11 @@
 import sys
 import tempfile
 from collections import defaultdict
+from collections.abc import Iterable
 from itertools import groupby
 from os.path import abspath, expanduser, isdir, join
 from subprocess import check_call
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Literal
 
 from constructor.utils import filename_dist
 
@@ -144,15 +145,43 @@ def _fetch(download_dir, precs):
     return list(dict.fromkeys(PrefixGraph(pc.iter_records()).graph))
 
 
-def check_duplicates_files(pc_recs, platform, duplicate_files="error"):
+def check_duplicates_files(
+    pc_recs: Iterable["PackageCacheRecord"],
+    platform: str,
+    duplicate_files: Literal["error", "warn", "skip"] = "error",
+    env_prefixes: dict["PackageCacheRecord", str] | None = None,
+) -> tuple[int, int, int]:
+    """
+    Check for duplicate files across packages and compute size/path metrics.
+
+    Iterates through all files in the provided package cache records to:
+    1. Detect duplicate files (same path in multiple packages)
+    2. Compute approximate tarball and extracted sizes
+    3. Track the longest relative file path (for MAX_PATH validation on Windows)
+
+    Args:
+        pc_recs: Package cache records to check.
+        platform: Target platform string (e.g., "win-64", "linux-64").
+        duplicate_files: How to handle duplicates - "error", "warn", or "skip".
+        env_prefixes: Optional dict mapping PackageCacheRecord -> path prefix string.
+            Used to account for extra_envs paths which are installed under
+            "envs/<name>/" rather than the base install directory. Records not
+            in this dict are assumed to be in the base environment (no prefix).
+
+    Returns:
+        Tuple of (approx_tarball_size, approx_extracted_size, max_relative_path_length)
+    """
     assert duplicate_files in ("warn", "skip", "error")
+    if env_prefixes is None:
+        env_prefixes = {}
 
     map_members_scase = defaultdict(set)
     map_members_icase = defaultdict(lambda: {"files": set(), "fns": set()})
 
     # Keep a min, 50MB buffer size
     total_tarball_size = 52428800
     total_extracted_pkgs_size = 52428800
+    max_relative_path_length = 0
 
     for pc_rec in pc_recs:
         fn = pc_rec.fn
@@ -161,8 +190,12 @@ def check_duplicates_files(pc_recs, platform, duplicate_files="error"):
         total_tarball_size += int(pc_rec.get("size", 0))
 
         paths_data = read_paths_json(extracted_package_dir).paths
+        env_prefix_len = len(env_prefixes.get(pc_rec, ""))
         for path_data in paths_data:
             short_path = path_data.path
+            max_relative_path_length = max(
+                max_relative_path_length, env_prefix_len + len(short_path)
+            )
             try:
                 size = path_data.size_in_bytes or getsize(join(extracted_package_dir, short_path))
             except AttributeError:
@@ -176,7 +209,7 @@ def check_duplicates_files(pc_recs, platform, duplicate_files="error"):
             map_members_icase[short_path_lower]["fns"].add(fn)
 
     if duplicate_files == "skip":
-        return total_tarball_size, total_extracted_pkgs_size
+        return total_tarball_size, total_extracted_pkgs_size, max_relative_path_length
 
     logger.info("Checking for duplicate files ...")
     for member in map_members_scase:
@@ -201,7 +234,7 @@ def check_duplicates_files(pc_recs, platform, duplicate_files="error"):
             else:
                 sys.exit(f"Error: {msg_str}")
 
-    return total_tarball_size, total_extracted_pkgs_size
+    return total_tarball_size, total_extracted_pkgs_size, max_relative_path_length
 
 
 def _precs_from_environment(environment, input_dir):
@@ -443,18 +476,24 @@ def _main(
             input_dir=input_dir,
         )
     if dry_run:
-        return None, None, None, None, None, None, None, None
+        return None, None, None, None, None, None, None, None, None
     pc_recs, _urls, dists, has_conda = _fetch_precs(
         precs, download_dir, transmute_file_type=transmute_file_type
     )
     all_pc_recs = pc_recs.copy()
 
     extra_envs_data = {}
+    env_prefixes = {}  # Maps pc_rec -> "envs/<name>/" prefix for max path calculation
     for env_name, env_precs in extra_envs_precs.items():
         env_pc_recs, env_urls, env_dists, _ = _fetch_precs(
             env_precs, download_dir, transmute_file_type=transmute_file_type
         )
         extra_envs_data[env_name] = {"_urls": env_urls, "_dists": env_dists, "_records": env_precs}
+        env_prefix = f"envs/{env_name}/"
+        for pc_rec in env_pc_recs:
+            existing_prefix = env_prefixes.get(pc_rec, "")
+            if len(env_prefix) > len(existing_prefix):
+                env_prefixes[pc_rec] = env_prefix
         all_pc_recs += env_pc_recs
 
     duplicate_files = "warn" if ignore_duplicate_files else "error"
@@ -463,8 +502,12 @@ def _main(
         duplicate_files = "skip"
 
     all_pc_recs = list({rec: None for rec in all_pc_recs})  # deduplicate
-    approx_tarballs_size, approx_pkgs_size = check_duplicates_files(
-        pc_recs, platform, duplicate_files=duplicate_files
+    # Pass all_pc_recs (base + extra_envs) to check_duplicates_files:
+    # - When extra_envs exists, duplicate_files="skip" so only sizes and max path are computed
+    # - When no extra_envs, all_pc_recs == pc_recs
+    # - env_prefixes dict ensures max path accounts for "envs/<name>/" prefix in extra_envs
+    approx_tarballs_size, approx_pkgs_size, max_relative_path_length = check_duplicates_files(
+        all_pc_recs, platform, duplicate_files=duplicate_files, env_prefixes=env_prefixes
     )
 
     return (
@@ -476,6 +519,7 @@ def _main(
         approx_pkgs_size,
         has_conda,
         extra_envs_data,
+        max_relative_path_length,
     )
 
 
@@ -529,6 +573,7 @@ def main(info, verbose=True, dry_run=False, conda_exe="conda.exe"):
             approx_pkgs_size,
             has_conda,
             extra_envs_info,
+            max_relative_path_length,
         ) = _main(
             name,
             version,
@@ -561,3 +606,4 @@ def main(info, verbose=True, dry_run=False, conda_exe="conda.exe"):
     info["_has_conda"] = has_conda
     # contains {env_name: [_dists, _urls, _records]} for each extra environment
     info["_extra_envs_info"] = extra_envs_info
+    info["_max_relative_path_length"] = max_relative_path_length

constructor/nsis/main.nsi.tmpl

@@ -130,6 +130,7 @@ ${Using:StrFunc} StrStr
 # are not written into install.log. STEP_LOG creates an intermittent file
 # that is output into these streams after the commands finish.
 !define STEP_LOG                      "$INSTDIR\.step.log"
+!define MAX_RELATIVE_PATH_LENGTH {{ max_relative_path_length }}
 
 var /global INIT_CONDA
 var /global REG_PY
@@ -1115,6 +1116,26 @@ Function OnDirectoryLeave
         ${EndIf}
     ${EndIf}
 
+    # MAX_PATH check - installation will fail if path exceeds 260 characters
+    ${If} $LongPathsEnabled == "0"
+        IntOp $0 $InstDirLen + ${MAX_RELATIVE_PATH_LENGTH}
+        IntOp $0 $0 + 1  # Account for path separator between install dir and relative path
+        ${If} $0 > 260
+            IntOp $1 260 - ${MAX_RELATIVE_PATH_LENGTH}
+            IntOp $1 $1 - 1  # Account for path separator
+            ${If} ${Silent}
+                ${Print} "::error:: The installation path is too long. Your path is $InstDirLen characters, but must be at most $1 characters."
+            ${Else}
+                MessageBox MB_OK|MB_ICONSTOP \
+                    "The installation path is too long.$\n$\n\
+                    Your path is $InstDirLen characters, but must be at most $1 characters.$\n$\n\
+                    Please choose a shorter installation path." \
+                    /SD IDOK
+            ${EndIf}
+            Abort
+        ${EndIf}
+    ${EndIf}
+
     # Call the CheckForSpaces function.
     Push $INSTDIR # Input string (install path).
     Call CheckForSpaces

constructor/winexe.py

@@ -252,6 +252,7 @@ def make_nsi(
     variables["initialize_by_default"] = info.get("initialize_by_default", None)
     variables["check_path_length"] = info.get("check_path_length", False)
     variables["check_path_spaces"] = info.get("check_path_spaces", True)
+    variables["max_relative_path_length"] = info.get("_max_relative_path_length", 0)
     variables["keep_pkgs"] = info.get("keep_pkgs") or False
     variables["pre_install_exists"] = bool(info.get("pre_install"))
     variables["post_install_exists"] = bool(info.get("post_install"))

docs/source/construct-yaml.md

@@ -552,11 +552,11 @@ interactive installation. (Windows only).
 
 Only applies if `register_python` is true.
 
-### `check_path_length`
+### ~~`check_path_length`~~
 
-Check the length of the path where the distribution is installed to ensure nodejs
-can be installed.  Raise a message to request shorter paths (less than 46 character)
-or enable long paths on windows > 10 (require admin right). Default is False. (Windows only).
+_Deprecated_. Path length validation is now always performed using the computed
+maximum relative path length from the package contents. This option will be
+removed in a future version. (Windows only).
 
 ### `check_path_spaces`
 

tests/requirements.txt

@@ -1,5 +1,6 @@
 pytest
 pytest-cov
+pytest-mock
 coverage
 jinja2
 ruamel.yaml

tests/test_fcp.py

@@ -4,7 +4,7 @@
 
 import pytest
 
-from constructor.fcp import check_duplicates, exclude_packages
+from constructor.fcp import check_duplicates, check_duplicates_files, exclude_packages
 
 
 class GenericObject:
@@ -64,3 +64,101 @@ def test_exclude_packages(values: tuple[..., GenericObject], expected_value):
     with context:
         packages = exclude_packages(*values)
         assert packages == expected_value
+
+
+class MockPathData:
+    """Represents a file path entry."""
+
+    def __init__(self, path):
+        self.path = path
+        self.size_in_bytes = 1  # must be non-zero to avoid filesystem access
+
+
+class MockPathsJson:
+    """Wraps a list of MockPathData entries."""
+
+    def __init__(self, paths):
+        self.paths = [MockPathData(p) for p in paths]
+
+
+class MockPackageCacheRecord:
+    """Represents a package record."""
+
+    def __init__(self, fn, extracted_package_dir, paths):
+        self.fn = fn
+        self.extracted_package_dir = extracted_package_dir
+        self._paths = paths
+
+    def get(self, key, default=None):
+        return default
+
+
+def test_check_duplicates_files_returns_max_path_length(mocker):
+    """Verify function returns max path length as third tuple element."""
+    pc_rec1 = MockPackageCacheRecord(
+        fn="pkg1-1.0.tar.bz2",
+        extracted_package_dir="/cache/pkg1",
+        paths=["lib/short.py"],  # 12 chars
+    )
+    pc_rec2 = MockPackageCacheRecord(
+        fn="pkg2-1.0.tar.bz2",
+        extracted_package_dir="/cache/pkg2",
+        paths=["lib/python3.10/site-packages/longer.py"],  # 38 chars
+    )
+
+    def read_paths_side_effect(extracted_dir):
+        if extracted_dir == "/cache/pkg1":
+            return MockPathsJson(pc_rec1._paths)
+        return MockPathsJson(pc_rec2._paths)
+
+    mock_read_paths = mocker.patch("constructor.fcp.read_paths_json")
+    mock_read_paths.side_effect = read_paths_side_effect
+
+    result = check_duplicates_files([pc_rec1, pc_rec2], "win-64", duplicate_files="skip")
+
+    assert len(result) == 3
+    _, _, max_path_len = result
+    assert max_path_len == 38
+
+
+def test_check_duplicates_files_empty_packages(mocker):
+    """Verify returns 0 when no packages provided."""
+    mock_read_paths = mocker.patch("constructor.fcp.read_paths_json")
+
+    result = check_duplicates_files([], "win-64", duplicate_files="skip")
+
+    assert len(result) == 3
+    assert result[2] == 0
+    mock_read_paths.assert_not_called()
+
+
+def test_check_duplicates_files_with_env_prefixes(mocker):
+    """Verify env_prefixes adds prefix length to max path calculation."""
+    pc_rec_base = MockPackageCacheRecord(
+        fn="base-pkg-1.0.tar.bz2",
+        extracted_package_dir="/cache/base-pkg",
+        paths=["lib/short.py"],  # 12 chars, no prefix -> 12
+    )
+    pc_rec_env = MockPackageCacheRecord(
+        fn="env-pkg-1.0.tar.bz2",
+        extracted_package_dir="/cache/env-pkg",
+        paths=["lib/short.py"],  # 12 chars, with "envs/myenv/" prefix (11) -> 23
+    )
+
+    def read_paths_side_effect(extracted_dir):
+        if extracted_dir == "/cache/base-pkg":
+            return MockPathsJson(pc_rec_base._paths)
+        return MockPathsJson(pc_rec_env._paths)
+
+    mock_read_paths = mocker.patch("constructor.fcp.read_paths_json")
+    mock_read_paths.side_effect = read_paths_side_effect
+
+    env_prefixes = {pc_rec_env: "envs/myenv/"}
+    result = check_duplicates_files(
+        [pc_rec_base, pc_rec_env], "win-64", duplicate_files="skip", env_prefixes=env_prefixes
+    )
+
+    assert len(result) == 3
+    _, _, max_path_len = result
+    # "envs/myenv/" (11) + "lib/short.py" (12) = 23
+    assert max_path_len == 23