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

@@ -7,6 +7,8 @@
 fcp (fetch conda packages) module
 """
 
+from __future__ import annotations
+
 import logging
 import os
 import shutil
@@ -38,6 +40,9 @@
 )
 
 if TYPE_CHECKING:
+    from collections.abc import Iterable
+    from typing import Literal
+
     from .conda_interface import PackageCacheRecord
 
 logger = logging.getLogger(__name__)
@@ -144,15 +149,44 @@ 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).
+            The prefix string should include the trailing slash (e.g., "envs/myenv/").
+
+    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 +195,12 @@ 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 +214,7 @@ 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 +239,7 @@ 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 +481,24 @@ 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 +507,12 @@ 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 +524,7 @@ def _main(
         approx_pkgs_size,
         has_conda,
         extra_envs_data,
+        max_relative_path_length,
     )
 
 
@@ -529,6 +578,7 @@ 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 +611,4 @@ 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
@@ -156,7 +157,6 @@ var /global ARGV_RegisterPython
 var /global ARGV_NoRegistry
 var /global ARGV_NoScripts
 var /global ARGV_NoShortcuts
-var /global ARGV_CheckPathLength
 var /global ARGV_QuietMode
 {%- if uninstall_with_conda_exe %}
 var /global ARGV_Uninst_RemoveConfigFiles
@@ -165,7 +165,6 @@ var /global ARGV_Uninst_RemoveCaches
 {%- endif %}
 
 var /global IsDomainUser
-var /global CheckPathLength
 var /global LongPathsEnabled
 var /global InstDirLen
 
@@ -292,7 +291,6 @@ Function SkipPageIfUACInnerInstance
 FunctionEnd
 
 Function InitializeVariables
-    StrCpy $CheckPathLength "{{ 1 if check_path_length else 0 }}"
     StrCpy $NO_REGISTRY "0"
 
     # Package cache option
@@ -365,7 +363,6 @@ FunctionEnd
                 /NoRegistry=[0|1] [default: AllUsers: 0, JustMe: 0]$\n\
                 /NoScripts=[0|1] [default: 0]$\n\
                 /NoShortcuts=[0|1] [default: 0]$\n\
-                /CheckPathLength=[0|1] [default: {{ 1 if check_path_length else 0 }}]$\n\
                 /? (show this help message)$\n\
                 /S (run in CLI/headless mode)$\n\
                 /Q (quiet mode, do not print output to console)$\n\
@@ -497,16 +494,6 @@ FunctionEnd
         StrCpy $Ana_CreateShortcuts_State ${BST_UNCHECKED}
     ${EndIf}
 
-    ClearErrors
-    ${GetOptions} $ARGV "/CheckPathLength=" $ARGV_CheckPathLength
-    ${IfNot} ${Errors}
-        ${If} $ARGV_CheckPathLength = "0"
-            StrCpy $CheckPathLength "0"
-        ${ElseIf} $ARGV_CheckPathLength = "1"
-            StrCpy $CheckPathLength "1"
-        ${EndIf}
-    ${EndIf}
-
     ClearErrors
     ${GetOptions} $ARGV "/Q" $ARGV_QuietMode
     ${IfNot} ${Errors}
@@ -1083,34 +1070,22 @@ Function OnDirectoryLeave
     ReadRegStr $LongPathsEnabled HKLM "SYSTEM\CurrentControlSet\Control\FileSystem" "LongPathsEnabled"
     StrLen $InstDirLen "$InstDir"
 
-    ${If} $CheckPathLength == "1"
-    ${AndIf} $LongPathsEnabled == "0"
-    ${AndIf} $InstDirLen > 46
-        ; With windows 10, we can enable support for long path, for earlier
-        ; version, suggest user to use shorter installation path
-        ${If} ${AtLeastWin10}
-        ${AndIfNot} $NO_REGISTRY = "1"
-            ; If we have admin right, we enable long path on windows
-            ${If} ${UAC_IsAdmin}
-                WriteRegDWORD HKLM "SYSTEM\CurrentControlSet\Control\FileSystem" "LongPathsEnabled" 1
-            ; If we don't have admin right, we suggest a shorter path or suggest to run with admin right
+    # 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}
-                ${Print} "::error:: The installation path should be shorter than 46 characters or \
-                             the installation requires administrator rights to enable long \
-                             path on Windows."
-                MessageBox MB_OK|MB_ICONSTOP "The installation path should be shorter than 46 characters or \
-                                              the installation requires administrator rights to enable long \
-                                              path on Windows." \
-                           /SD IDOK
-                Abort
+                MessageBox MB_OK|MB_ICONSTOP \
+                    "The installation path is too long.$\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}
-        ; If we don't have admin right, we suggest a shorter path or suggest to run with admin right
-        ${Else}
-            ${Print} "::error:: The installation path should be shorter than 46 characters. \
-                         Please choose another location."
-            MessageBox MB_OK|MB_ICONSTOP "The installation path should be shorter than 46 characters. \
-                                          Please choose another location." \
-                       /SD IDOK
             Abort
         ${EndIf}
     ${EndIf}

constructor/winexe.py

@@ -250,8 +250,8 @@ def make_nsi(
     variables.update(ns_platform(info["_platform"]))
     variables["initialize_conda"] = info.get("initialize_conda", "classic")
     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_examples.py

@@ -162,7 +162,7 @@ def _check_installer_log(install_dir):
             "Once you have installed it, set NSIS_USING_LOG_BUILD=1.\n"
             "Otherwise, this usually means that the destination folder could not be created.\n"
             "Possible causes: permissions, non-supported characters, long paths...\n"
-            "Consider setting 'check_path_spaces' and 'check_path_length' to 'False'."
+            "Consider setting 'check_path_spaces' to 'False'."
         )
     if error_lines:
         raise AssertionError("\n".join(error_lines))