Merge pull request #867 from ahoarau/fix-jrl-options-cond

jrl_option: fix condition handling on reconfigure

Author: nim65s

CHANGELOG.md

@@ -8,6 +8,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 - jrl_release: add package.xml
 - jrl_check_python_module: add version handling by @ahoarau
+- jrl_option: fix condition handling on reconfigure and support parent project normal variables (CMP0077)
 
 ## [2.2.4] - 2026-08-07
 

v2/docs/api.md

@@ -881,7 +881,8 @@ jrl_legacy_option(
 
 ### Description
   Migrate a legacy option value to a new option name and emit a deprecation warning.
-  If the old option is defined, its value is migrated to the new option.
+  If the old option is defined, its value is migrated to the new option and the old cache
+  entry is removed, so the migration happens only once.
   The NEW_OPTION must already exist in the cache (created via jrl_option or option()).
   The help text is automatically retrieved from the NEW_OPTION cache property.
 
@@ -914,19 +915,27 @@ jrl_option(
 
 
 ### Description
-  Declare a cache BOOL option with optional conditional availability and legacy name migration.
-  When `CONDITION` evaluates to false, the option is forced to the `FALLBACK` value (default OFF) with FORCE and hidden.
+  Declare a cache BOOL (all CMake options are booleans) option, with an optional condition and an optional legacy name.
+  When `CONDITION` is false, the option is forced to the `FALLBACK` value and hidden.
+  When `CONDITION` becomes true again on a reconfigure, the option is shown again and
+  gets back the value the user asked for, or `<default_value>` if they never set one.
   When `LEGACY_NAME` is set, its value is migrated to `<name>` and a deprecation
   warning is emitted.
 
+  Like CMake `option()` with policy `CMP0077`, a normal variable of the same name takes
+  precedence without creating a cache entry, allowing a parent project to set options
+  before `add_subdirectory()` or `FetchContent`. If `CONDITION` evaluates to false, the
+  fallback value is still enforced.
+
 
 ### Arguments
 * `name`: The option name.
 * `help_text`: The cache entry help string.
 * `default_value`: The default value (ON/OFF).
 * `CONDITION`: CMake condition string to evaluate (optional). If false, the option will be forced to FALLBACK value.
-* `FALLBACK`: Value to force when CONDITION is false (optional).
-* `LEGACY_NAME`: Deprecated option name to migrate (optional).
+    A semicolon-separated list is also accepted, in which case every element must be true, as in `cmake_dependent_option()`.
+* `FALLBACK`: Value to force when CONDITION is false (required when CONDITION is given).
+* `LEGACY_NAME`: Deprecated option name to migrate (optional). It is an alias for `<name>`, so it goes through `CONDITION` as well.
 
 
 ### Example
@@ -941,6 +950,12 @@ jrl_option(
     LEGACY_NAME BUILD_PYTHON_BINDINGS
 )
 ```
+
+`BUILD_PYTHON` follows its condition from one configure to the next:
+```bash
+cmake -B build -DBUILD_SHARED_LIBS=OFF # BUILD_PYTHON is forced to OFF and hidden
+cmake build -DBUILD_SHARED_LIBS=ON     # BUILD_PYTHON is ON and visible again
+```
 # `jrl_generate_options_markdown_summary`
 
 ```cpp