Merge pull request #3483 from grossag/topic/grossag/compoundactionscan

Add support for scanning multiple entries in an action string

7 files changed, 362 insertions, 211 deletions

diff --git a/src/CHANGES.txt b/src/CHANGES.txt
index 9d2f51c..025e046 100755
--- a/src/CHANGES.txt
+++ b/src/CHANGES.txt
@@ -28,6 +28,10 @@ RELEASE  VERSION/DATE TO BE FILLED IN LATER
     - Updated design doc to use the correct syntax for Depends()
 
   From Adam Gross:
+    - Added support for scanning multiple entries in an action string if
+      IMPLICIT_COMMAND_DEPENDENCIES is set to 2. This opts into more thorough
+      action scanning where every string in the command is scanned to determine
+      if it is a non-source and non-target path.
     - Added support for taking instances of the Value class as implicit
       dependencies.
     - Added new module SCons.Scanner.Python to allow scanning .py files.
diff --git a/src/engine/SCons/Action.py b/src/engine/SCons/Action.py
index 0b7282c..8a8cf27 100644
--- a/src/engine/SCons/Action.py
+++ b/src/engine/SCons/Action.py
@@ -968,11 +968,33 @@ class CommandAction(_ActionAction):
             return env.subst_target_source(cmd, SUBST_SIG, target, source)
 
     def get_implicit_deps(self, target, source, env, executor=None):
+        """Return the implicit dependencies of this action's command line."""
         icd = env.get('IMPLICIT_COMMAND_DEPENDENCIES', True)
         if is_String(icd) and icd[:1] == '$':
             icd = env.subst(icd)
+
         if not icd or icd in ('0', 'None'):
             return []
+
+        try:
+            icd_int = int(icd)
+        except ValueError:
+            icd_int = None
+
+        if (icd_int and icd_int > 1) or icd == 'all':
+            # An integer value greater than 1 specifies the number of entries
+            # to scan. "all" means to scan all.
+            return self._get_implicit_deps_heavyweight(target, source, env, executor, icd_int)
+        else:
+            # Everything else (usually 1 or True) means that we want
+            # lightweight dependency scanning.
+            return self._get_implicit_deps_lightweight(target, source, env, executor)
+
+    def _get_implicit_deps_lightweight(self, target, source, env, executor):
+        """
+        Lightweight dependency scanning involves only scanning the first entry
+        in an action string, even if it contains &&.
+        """
         from SCons.Subst import SUBST_SIG
         if executor:
             cmd_list = env.subst_list(self.cmd_list, SUBST_SIG, executor=executor)
@@ -990,6 +1012,65 @@ class CommandAction(_ActionAction):
                     res.append(env.fs.File(d))
         return res
 
+    def _get_implicit_deps_heavyweight(self, target, source, env, executor,
+                                       icd_int):
+        """
+        Heavyweight dependency scanning involves scanning more than just the
+        first entry in an action string. The exact behavior depends on the
+        value of icd_int. Only files are taken as implicit dependencies;
+        directories are ignored.
+
+        If icd_int is an integer value, it specifies the number of entries to
+        scan for implicit dependencies. Action strings are also scanned after
+        a &&. So for example, if icd_int=2 and the action string is
+        "cd <some_dir> && $PYTHON $SCRIPT_PATH <another_path>", the implicit
+        dependencies would be the path to the python binary and the path to the
+        script.
+
+        If icd_int is None, all entries are scanned for implicit dependencies.
+        """
+
+        # Avoid circular and duplicate dependencies by not providing source,
+        # target, or executor to subst_list. This causes references to
+        # $SOURCES, $TARGETS, and all related variables to disappear.
+        from SCons.Subst import SUBST_SIG
+        cmd_list = env.subst_list(self.cmd_list, SUBST_SIG, conv=lambda x: x)
+        res = []
+
+        for cmd_line in cmd_list:
+            if cmd_line:
+                entry_count = 0
+                for entry in cmd_line:
+                    d = str(entry)
+                    if ((icd_int is None or entry_count < icd_int) and
+                            not d.startswith(('&', '-', '/') if os.name == 'nt'
+                                             else ('&', '-'))):
+                        m = strip_quotes.match(d)
+                        if m:
+                            d = m.group(1)
+
+                        if d:
+                            # Resolve the first entry in the command string using
+                            # PATH, which env.WhereIs() looks in.
+                            # For now, only match files, not directories.
+                            p = os.path.abspath(d) if os.path.isfile(d) else None
+                            if not p and entry_count == 0:
+                                p = env.WhereIs(d)
+
+                            if p:
+                                res.append(env.fs.File(p))
+
+                        entry_count = entry_count + 1
+                    else:
+                        entry_count = 0 if d == '&&' else entry_count + 1
+
+        # Despite not providing source and target to env.subst() above, we
+        # can still end up with sources in this list. For example, files in
+        # LIBS will still resolve in env.subst(). This won't result in
+        # circular dependencies, but it causes problems with cache signatures
+        # changing between full and incremental builds.
+        return [r for r in res if r not in target and r not in source]
+
 
 class CommandGeneratorAction(ActionBase):
     """Class for command-generator actions."""
diff --git a/src/engine/SCons/Action.xml b/src/engine/SCons/Action.xml
index 7a8194e..d85af3b 100644
--- a/src/engine/SCons/Action.xml
+++ b/src/engine/SCons/Action.xml
@@ -58,6 +58,45 @@ not be added to the targets
 built with that construction environment.
 </para>
 
+<para>
+If the construction variable
+&cv-IMPLICIT_COMMAND_DEPENDENCIES;
+is set to <literal>2</literal> or higher,
+then that number of entries in the command
+string will be scanned for relative or absolute
+paths. The count will reset after any
+<literal>&&</literal> entries are found.
+The first command in the action string and
+the first after any <literal>&&</literal>
+entries will be found by searching the
+<varname>PATH</varname> variable in the
+<varname>ENV</varname> environment used to
+execute the command. All other commands will
+only be found if they are absolute paths or
+valid paths relative to the working directory.
+</para>
+
+<para>
+If the construction variable
+&cv-IMPLICIT_COMMAND_DEPENDENCIES;
+is set to <literal>all</literal>, then
+all entries in all command strings will be
+scanned for relative or absolute paths. If
+any are present, they will be added as
+implicit dependencies to the targets built
+with that construction environment.
+not be added to the targets built with that
+construction environment. The first command
+in the action string and the first after any
+<literal>&&</literal> entries will be found
+by searching the <varname>PATH</varname>
+variable in the <varname>ENV</varname>
+environment used to execute the command.
+All other commands will only be found if they
+are absolute paths or valid paths relative
+to the working directory.
+</para>
+
 <example_commands>
 env = Environment(IMPLICIT_COMMAND_DEPENDENCIES = 0)
 </example_commands>
diff --git a/test/Batch/action-changed.py b/test/Batch/action-changed.py
index b2b1673..da5115e 100644
--- a/test/Batch/action-changed.py
+++ b/test/Batch/action-changed.py
@@ -33,7 +33,11 @@ import os
 
 import TestSCons
 
-python = TestSCons.python
+# swap slashes because on py3 on win32 inside the generated build.py
+# the backslashes are getting interpretted as unicode which is
+# invalid.
+python = TestSCons.python.replace('\\','//')
+_python_ = TestSCons._python_
 
 test = TestSCons.TestSCons()
 
@@ -53,17 +57,21 @@ sys.exit(0)
 test.write('build.py', build_py_contents % (python, 'one'))
 os.chmod(test.workpath('build.py'), 0o755)
 
+build_py_workpath = test.workpath('build.py')
+
+# Provide IMPLICIT_COMMAND_DEPENDENCIES=2 so we take a dependency on build.py.
+# Without that, we only scan the first entry in the action string.
 test.write('SConstruct', """
-env = Environment()
+env = Environment(IMPLICIT_COMMAND_DEPENDENCIES=2)
 env.PrependENVPath('PATHEXT', '.PY')
-bb = Action(r'"%s" $CHANGED_TARGETS -- $CHANGED_SOURCES',
+bb = Action(r'%(_python_)s "%(build_py_workpath)s" $CHANGED_TARGETS -- $CHANGED_SOURCES',
             batch_key=True,
             targets='CHANGED_TARGETS')
 env['BUILDERS']['Batch'] = Builder(action=bb)
 env.Batch('f1.out', 'f1.in')
 env.Batch('f2.out', 'f2.in')
 env.Batch('f3.out', 'f3.in')
-""" % test.workpath('build.py'))
+""" % locals())
 
 test.write('f1.in', "f1.in\n")
 test.write('f2.in', "f2.in\n")
diff --git a/test/Repository/Program.py b/test/Repository/Program.py
index 1eb18d8..9e8af77 100644
--- a/test/Repository/Program.py
+++ b/test/Repository/Program.py
@@ -32,25 +32,22 @@ if sys.platform == 'win32':
 else:
     _exe = ''
 
-test = TestSCons.TestSCons()
-
-
-
-# First, test a single repository.
-test.subdir('repository', 'work1')
-
-repository = test.workpath('repository')
-repository_foo_c = test.workpath('repository', 'foo.c')
-work1_foo = test.workpath('work1', 'foo' + _exe)
-work1_foo_c = test.workpath('work1', 'foo.c')
-
-test.write(['work1', 'SConstruct'], r"""
+for implicit_deps in ['0', '1', '2', 'all']:
+    # First, test a single repository.
+    test = TestSCons.TestSCons()
+    test.subdir('repository', 'work1')
+    repository = test.workpath('repository')
+    repository_foo_c = test.workpath('repository', 'foo.c')
+    work1_foo = test.workpath('work1', 'foo' + _exe)
+    work1_foo_c = test.workpath('work1', 'foo.c')
+
+    test.write(['work1', 'SConstruct'], r"""
 Repository(r'%s')
-env = Environment()
+env = Environment(IMPLICIT_COMMAND_DEPENDENCIES=%s)
 env.Program(target= 'foo', source = Split('aaa.c bbb.c foo.c'))
-""" % repository)
+""" % (repository, implicit_deps))
 
-test.write(['repository', 'aaa.c'], r"""
+    test.write(['repository', 'aaa.c'], r"""
 #include <stdio.h>
 void
 aaa(void)
@@ -59,7 +56,7 @@ aaa(void)
 }
 """)
 
-test.write(['repository', 'bbb.c'], r"""
+    test.write(['repository', 'bbb.c'], r"""
 #include <stdio.h>
 void
 bbb(void)
@@ -68,7 +65,7 @@ bbb(void)
 }
 """)
 
-test.write(['repository', 'foo.c'], r"""
+    test.write(['repository', 'foo.c'], r"""
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -85,21 +82,21 @@ main(int argc, char *argv[])
 }
 """)
 
-# Make the entire repository non-writable, so we'll detect
-# if we try to write into it accidentally.
-test.writable('repository', 0)
+    # Make the entire repository non-writable, so we'll detect
+    # if we try to write into it accidentally.
+    test.writable('repository', 0)
 
-test.run(chdir = 'work1', arguments = '.')
+    test.run(chdir = 'work1', arguments = '.')
 
-test.run(program = work1_foo, stdout = """repository/aaa.c
+    test.run(program = work1_foo, stdout = """repository/aaa.c
 repository/bbb.c
 repository/foo.c
 """)
 
-test.up_to_date(chdir = 'work1', arguments = '.')
+    test.up_to_date(chdir = 'work1', arguments = '.')
 
-#
-test.write(['work1', 'bbb.c'], r"""
+    #
+    test.write(['work1', 'bbb.c'], r"""
 #include <stdio.h>
 void
 bbb(void)
@@ -108,17 +105,17 @@ bbb(void)
 }
 """)
 
-test.run(chdir = 'work1', arguments = '.')
+    test.run(chdir = 'work1', arguments = '.')
 
-test.run(program = work1_foo, stdout = """repository/aaa.c
+    test.run(program = work1_foo, stdout = """repository/aaa.c
 work1/bbb.c
 repository/foo.c
 """)
 
-test.up_to_date(chdir = 'work1', arguments = '.')
+    test.up_to_date(chdir = 'work1', arguments = '.')
 
-#
-test.write(['work1', 'aaa.c'], r"""
+    #
+    test.write(['work1', 'aaa.c'], r"""
 #include <stdio.h>
 void
 aaa(void)
@@ -127,7 +124,7 @@ aaa(void)
 }
 """)
 
-test.write(['work1', 'foo.c'], r"""
+    test.write(['work1', 'foo.c'], r"""
 #include <stdio.h>
 #include <stdlib.h>
 extern void aaa(void);
@@ -143,57 +140,57 @@ main(int argc, char *argv[])
 }
 """)
 
-test.run(chdir = 'work1', arguments = '.')
+    test.run(chdir = 'work1', arguments = '.')
 
-test.run(program = work1_foo, stdout = """work1/aaa.c
+    test.run(program = work1_foo, stdout = """work1/aaa.c
 work1/bbb.c
 work1/foo.c
 """)
 
-test.up_to_date(chdir = 'work1', arguments = '.')
+    test.up_to_date(chdir = 'work1', arguments = '.')
 
-#
-test.unlink(['work1', 'aaa.c'])
+    #
+    test.unlink(['work1', 'aaa.c'])
 
-test.run(chdir = 'work1', arguments = '.')
+    test.run(chdir = 'work1', arguments = '.')
 
-test.run(program = work1_foo, stdout = """repository/aaa.c
+    test.run(program = work1_foo, stdout = """repository/aaa.c
 work1/bbb.c
 work1/foo.c
 """)
 
-test.up_to_date(chdir = 'work1', arguments = '.')
+    test.up_to_date(chdir = 'work1', arguments = '.')
 
-#
-test.unlink(['work1', 'bbb.c'])
-test.unlink(['work1', 'foo.c'])
+    #
+    test.unlink(['work1', 'bbb.c'])
+    test.unlink(['work1', 'foo.c'])
 
-test.run(chdir = 'work1', arguments = '.')
+    test.run(chdir = 'work1', arguments = '.')
 
-test.run(program = work1_foo, stdout = """repository/aaa.c
+    test.run(program = work1_foo, stdout = """repository/aaa.c
 repository/bbb.c
 repository/foo.c
 """)
 
-test.up_to_date(chdir = 'work1', arguments = '.')
+    test.up_to_date(chdir = 'work1', arguments = '.')
 
 
 
-# Now, test multiple repositories.
-test.subdir('repository.new', 'repository.old', 'work2')
+    # Now, test multiple repositories.
+    test.subdir('repository.new', 'repository.old', 'work2')
 
-repository_new = test.workpath('repository.new')
-repository_old = test.workpath('repository.old')
-work2_foo = test.workpath('work2', 'foo' + _exe)
+    repository_new = test.workpath('repository.new')
+    repository_old = test.workpath('repository.old')
+    work2_foo = test.workpath('work2', 'foo' + _exe)
 
-test.write(['work2', 'SConstruct'], r"""
+    test.write(['work2', 'SConstruct'], r"""
 Repository(r'%s')
 Repository(r'%s')
 env = Environment()
 env.Program(target= 'foo', source = Split('aaa.c bbb.c foo.c'))
 """ % (repository_new, repository_old))
 
-test.write(['repository.old', 'aaa.c'], r"""
+    test.write(['repository.old', 'aaa.c'], r"""
 #include <stdio.h>
 void
 aaa(void)
@@ -202,7 +199,7 @@ aaa(void)
 }
 """)
 
-test.write(['repository.old', 'bbb.c'], r"""
+    test.write(['repository.old', 'bbb.c'], r"""
 #include <stdio.h>
 void
 bbb(void)
@@ -211,7 +208,7 @@ bbb(void)
 }
 """)
 
-test.write(['repository.old', 'foo.c'], r"""
+    test.write(['repository.old', 'foo.c'], r"""
 #include <stdio.h>
 #include <stdlib.h>
 extern void aaa(void);
@@ -227,24 +224,24 @@ main(int argc, char *argv[])
 }
 """)
 
-# Make both repositories non-writable, so we'll detect
-# if we try to write into it accidentally.
-test.writable('repository.new', 0)
-test.writable('repository.old', 0)
+    # Make both repositories non-writable, so we'll detect
+    # if we try to write into it accidentally.
+    test.writable('repository.new', 0)
+    test.writable('repository.old', 0)
 
-test.run(chdir = 'work2', arguments = '.')
+    test.run(chdir = 'work2', arguments = '.')
 
-test.run(program = work2_foo, stdout = """repository.old/aaa.c
+    test.run(program = work2_foo, stdout = """repository.old/aaa.c
 repository.old/bbb.c
 repository.old/foo.c
 """)
 
-test.up_to_date(chdir = 'work2', arguments = '.')
+    test.up_to_date(chdir = 'work2', arguments = '.')
 
-#
-test.writable('repository.new', 1)
+    #
+    test.writable('repository.new', 1)
 
-test.write(['repository.new', 'aaa.c'], r"""
+    test.write(['repository.new', 'aaa.c'], r"""
 #include <stdio.h>
 #include <stdlib.h>
 void
@@ -254,7 +251,7 @@ aaa(void)
 }
 """)
 
-test.write(['work2', 'bbb.c'], r"""
+    test.write(['work2', 'bbb.c'], r"""
 #include <stdio.h>
 #include <stdlib.h>
 void
@@ -264,20 +261,20 @@ bbb(void)
 }
 """)
 
-#
-test.writable('repository.new', 0)
+    #
+    test.writable('repository.new', 0)
 
-test.run(chdir = 'work2', arguments = '.')
+    test.run(chdir = 'work2', arguments = '.')
 
-test.run(program = work2_foo, stdout = """repository.new/aaa.c
+    test.run(program = work2_foo, stdout = """repository.new/aaa.c
 work2/bbb.c
 repository.old/foo.c
 """)
 
-test.up_to_date(chdir = 'work2', arguments = '.')
+    test.up_to_date(chdir = 'work2', arguments = '.')
 
-#
-test.write(['work2', 'aaa.c'], r"""
+    #
+    test.write(['work2', 'aaa.c'], r"""
 #include <stdio.h>
 #include <stdlib.h>
 void
@@ -287,7 +284,7 @@ aaa(void)
 }
 """)
 
-test.write(['work2', 'foo.c'], r"""
+    test.write(['work2', 'foo.c'], r"""
 #include <stdio.h>
 #include <stdlib.h>
 extern void aaa(void);
@@ -303,59 +300,59 @@ main(int argc, char *argv[])
 }
 """)
 
-#
-test.run(chdir = 'work2', arguments = '.')
+    #
+    test.run(chdir = 'work2', arguments = '.')
 
-test.run(program = work2_foo, stdout = """work2/aaa.c
+    test.run(program = work2_foo, stdout = """work2/aaa.c
 work2/bbb.c
 work2/foo.c
 """)
 
-test.up_to_date(chdir = 'work2', arguments = '.')
+    test.up_to_date(chdir = 'work2', arguments = '.')
 
-#
-test.unlink(['work2', 'aaa.c'])
-test.unlink(['work2', 'bbb.c'])
+    #
+    test.unlink(['work2', 'aaa.c'])
+    test.unlink(['work2', 'bbb.c'])
 
-#
-test.run(chdir = 'work2', arguments = '.')
+    #
+    test.run(chdir = 'work2', arguments = '.')
 
-test.run(program = work2_foo, stdout = """repository.new/aaa.c
+    test.run(program = work2_foo, stdout = """repository.new/aaa.c
 repository.old/bbb.c
 work2/foo.c
 """)
 
-test.up_to_date(chdir = 'work2', arguments = '.')
+    test.up_to_date(chdir = 'work2', arguments = '.')
 
-#
-test.unlink(['work2', 'foo.c'])
+    #
+    test.unlink(['work2', 'foo.c'])
 
-#
-test.run(chdir = 'work2', arguments = '.')
+    #
+    test.run(chdir = 'work2', arguments = '.')
 
-test.run(program = work2_foo, stdout = """repository.new/aaa.c
+    test.run(program = work2_foo, stdout = """repository.new/aaa.c
 repository.old/bbb.c
 repository.old/foo.c
 """)
 
-test.up_to_date(chdir = 'work2', arguments = '.')
+    test.up_to_date(chdir = 'work2', arguments = '.')
 
-#
-test.writable('repository.new', 1)
+    #
+    test.writable('repository.new', 1)
 
-test.unlink(['repository.new', 'aaa.c'])
+    test.unlink(['repository.new', 'aaa.c'])
 
-test.writable('repository.new', 0)
+    test.writable('repository.new', 0)
 
-#
-test.run(chdir = 'work2', arguments = '.')
+    #
+    test.run(chdir = 'work2', arguments = '.')
 
-test.run(program = work2_foo, stdout = """repository.old/aaa.c
+    test.run(program = work2_foo, stdout = """repository.old/aaa.c
 repository.old/bbb.c
 repository.old/foo.c
 """)
 
-test.up_to_date(chdir = 'work2', arguments = '.')
+    test.up_to_date(chdir = 'work2', arguments = '.')
 
 
 #
diff --git a/test/Repository/StaticLibrary.py b/test/Repository/StaticLibrary.py
index 4f8160c..acd4b83 100644
--- a/test/Repository/StaticLibrary.py
+++ b/test/Repository/StaticLibrary.py
@@ -30,35 +30,37 @@ import TestSCons
 _obj = TestSCons._obj
 _exe = TestSCons._exe
 
-test = TestSCons.TestSCons()
-
-#
-test.subdir('repository', 'work1', 'work2', 'work3')
-
-#
-workpath_repository = test.workpath('repository')
-repository_aaa_obj = test.workpath('repository', 'aaa' + _obj)
-repository_bbb_obj = test.workpath('repository', 'bbb' + _obj)
-repository_foo_obj = test.workpath('repository', 'foo' + _obj)
-repository_foo = test.workpath('repository', 'foo' + _exe)
-work1_foo = test.workpath('work1', 'foo' + _exe)
-work2_aaa_obj = test.workpath('work2', 'aaa' + _obj)
-work2_foo_obj = test.workpath('work2', 'foo' + _obj)
-work2_foo = test.workpath('work2', 'foo' + _exe)
-work3_aaa_obj = test.workpath('work3', 'aaa' + _obj)
-work3_bbb_obj = test.workpath('work3', 'bbb' + _obj)
-work3_foo = test.workpath('work3', 'foo' + _exe)
-
-opts = '-Y ' + workpath_repository
-
-#
-test.write(['repository', 'SConstruct'], """
-env = Environment(LIBS = ['xxx'], LIBPATH = '.')
+for implicit_deps in ['0', '1', '2', 'all']:
+    test = TestSCons.TestSCons()
+
+    #
+    test.subdir('repository', 'work1', 'work2', 'work3')
+
+    #
+    workpath_repository = test.workpath('repository')
+    repository_aaa_obj = test.workpath('repository', 'aaa' + _obj)
+    repository_bbb_obj = test.workpath('repository', 'bbb' + _obj)
+    repository_foo_obj = test.workpath('repository', 'foo' + _obj)
+    repository_foo = test.workpath('repository', 'foo' + _exe)
+    work1_foo = test.workpath('work1', 'foo' + _exe)
+    work2_aaa_obj = test.workpath('work2', 'aaa' + _obj)
+    work2_foo_obj = test.workpath('work2', 'foo' + _obj)
+    work2_foo = test.workpath('work2', 'foo' + _exe)
+    work3_aaa_obj = test.workpath('work3', 'aaa' + _obj)
+    work3_bbb_obj = test.workpath('work3', 'bbb' + _obj)
+    work3_foo = test.workpath('work3', 'foo' + _exe)
+
+    opts = '-Y ' + workpath_repository
+
+    #
+    test.write(['repository', 'SConstruct'], """
+env = Environment(LIBS = ['xxx'], LIBPATH = '.',
+                  IMPLICIT_COMMAND_DEPENDENCIES=%s)
 env.Library(target = 'xxx', source = ['aaa.c', 'bbb.c'])
 env.Program(target = 'foo', source = 'foo.c')
-""")
+""" % implicit_deps)
 
-test.write(['repository', 'aaa.c'], r"""
+    test.write(['repository', 'aaa.c'], r"""
 #include <stdio.h>
 #include <stdlib.h>
 void
@@ -68,7 +70,7 @@ aaa(void)
 }
 """)
 
-test.write(['repository', 'bbb.c'], r"""
+    test.write(['repository', 'bbb.c'], r"""
 #include <stdio.h>
 #include <stdlib.h>
 void
@@ -78,7 +80,7 @@ bbb(void)
 }
 """)
 
-test.write(['repository', 'foo.c'], r"""
+    test.write(['repository', 'foo.c'], r"""
 #include <stdio.h>
 #include <stdlib.h>
 extern void aaa(void);
@@ -94,29 +96,29 @@ main(int argc, char *argv[])
 }
 """)
 
-# Make the repository non-writable,
-# so we'll detect if we try to write into it accidentally.
-test.writable('repository', 0)
+    # Make the repository non-writable,
+    # so we'll detect if we try to write into it accidentally.
+    test.writable('repository', 0)
 
-#
-test.run(chdir = 'work1', options = opts, arguments = ".",
-         stderr=TestSCons.noisy_ar,
-         match=TestSCons.match_re_dotall)
+    #
+    test.run(chdir = 'work1', options = opts, arguments = ".",
+             stderr=TestSCons.noisy_ar,
+             match=TestSCons.match_re_dotall)
 
-test.run(program = work1_foo, stdout =
+    test.run(program = work1_foo, stdout =
 """repository/aaa.c
 repository/bbb.c
 repository/foo.c
 """)
 
-test.fail_test(os.path.exists(repository_aaa_obj))
-test.fail_test(os.path.exists(repository_bbb_obj))
-test.fail_test(os.path.exists(repository_foo_obj))
-test.fail_test(os.path.exists(repository_foo))
+    test.fail_test(os.path.exists(repository_aaa_obj))
+    test.fail_test(os.path.exists(repository_bbb_obj))
+    test.fail_test(os.path.exists(repository_foo_obj))
+    test.fail_test(os.path.exists(repository_foo))
 
-test.up_to_date(chdir = 'work1', options = opts, arguments = ".")
+    test.up_to_date(chdir = 'work1', options = opts, arguments = ".")
 
-test.write(['work1', 'bbb.c'], r"""
+    test.write(['work1', 'bbb.c'], r"""
 #include <stdio.h>
 #include <stdlib.h>
 void
@@ -126,49 +128,49 @@ bbb(void)
 }
 """)
 
-test.run(chdir = 'work1', options = opts, arguments = ".",
-         stderr=TestSCons.noisy_ar,
-         match=TestSCons.match_re_dotall)
+    test.run(chdir = 'work1', options = opts, arguments = ".",
+             stderr=TestSCons.noisy_ar,
+             match=TestSCons.match_re_dotall)
 
-test.run(program = work1_foo, stdout =
+    test.run(program = work1_foo, stdout =
 """repository/aaa.c
 work1/bbb.c
 repository/foo.c
 """)
 
-test.fail_test(os.path.exists(repository_aaa_obj))
-test.fail_test(os.path.exists(repository_bbb_obj))
-test.fail_test(os.path.exists(repository_foo_obj))
-test.fail_test(os.path.exists(repository_foo))
+    test.fail_test(os.path.exists(repository_aaa_obj))
+    test.fail_test(os.path.exists(repository_bbb_obj))
+    test.fail_test(os.path.exists(repository_foo_obj))
+    test.fail_test(os.path.exists(repository_foo))
 
-test.up_to_date(chdir = 'work1', options = opts, arguments = ".")
+    test.up_to_date(chdir = 'work1', options = opts, arguments = ".")
 
-#
-test.writable('repository', 1)
+    #
+    test.writable('repository', 1)
 
-test.run(chdir = 'repository', options = opts, arguments = ".",
-         stderr=TestSCons.noisy_ar,
-         match=TestSCons.match_re_dotall)
+    test.run(chdir = 'repository', options = opts, arguments = ".",
+             stderr=TestSCons.noisy_ar,
+             match=TestSCons.match_re_dotall)
 
-test.run(program = repository_foo, stdout =
+    test.run(program = repository_foo, stdout =
 """repository/aaa.c
 repository/bbb.c
 repository/foo.c
 """)
 
-test.fail_test(not os.path.exists(repository_aaa_obj))
-test.fail_test(not os.path.exists(repository_bbb_obj))
-test.fail_test(not os.path.exists(repository_foo_obj))
+    test.fail_test(not os.path.exists(repository_aaa_obj))
+    test.fail_test(not os.path.exists(repository_bbb_obj))
+    test.fail_test(not os.path.exists(repository_foo_obj))
 
-test.up_to_date(chdir = 'repository', options = opts, arguments = ".")
+    test.up_to_date(chdir = 'repository', options = opts, arguments = ".")
 
-#
-test.writable('repository', 0)
+    #
+    test.writable('repository', 0)
 
-#
-test.up_to_date(chdir = 'work2', options = opts, arguments = ".")
+    #
+    test.up_to_date(chdir = 'work2', options = opts, arguments = ".")
 
-test.write(['work2', 'bbb.c'], r"""
+    test.write(['work2', 'bbb.c'], r"""
 #include <stdio.h>
 #include <stdlib.h>
 void
@@ -178,25 +180,25 @@ bbb(void)
 }
 """)
 
-test.run(chdir = 'work2', options = opts, arguments = ".",
-         stderr=TestSCons.noisy_ar,
-         match=TestSCons.match_re_dotall)
+    test.run(chdir = 'work2', options = opts, arguments = ".",
+             stderr=TestSCons.noisy_ar,
+             match=TestSCons.match_re_dotall)
 
-test.run(program = work2_foo, stdout =
+    test.run(program = work2_foo, stdout =
 """repository/aaa.c
 work2/bbb.c
 repository/foo.c
 """)
 
-test.fail_test(os.path.exists(work2_aaa_obj))
-test.fail_test(os.path.exists(work2_foo_obj))
+    test.fail_test(os.path.exists(work2_aaa_obj))
+    test.fail_test(os.path.exists(work2_foo_obj))
 
-test.up_to_date(chdir = 'work2', options = opts, arguments = ".")
+    test.up_to_date(chdir = 'work2', options = opts, arguments = ".")
 
-#
-test.up_to_date(chdir = 'work3', options = opts, arguments = ".")
+    #
+    test.up_to_date(chdir = 'work3', options = opts, arguments = ".")
 
-test.write(['work3', 'foo.c'], r"""
+    test.write(['work3', 'foo.c'], r"""
 #include <stdio.h>
 #include <stdlib.h>
 extern void aaa(void);
@@ -212,18 +214,19 @@ main(int argc, char *argv[])
 }
 """)
 
-test.run(chdir = 'work3', options = opts, arguments = ".")
+    test.run(chdir = 'work3', options = opts, arguments = ".")
 
-test.run(program = work3_foo, stdout =
+    test.run(program = work3_foo, stdout =
 """repository/aaa.c
 repository/bbb.c
 work3/foo.c
 """)
 
-test.fail_test(os.path.exists(work3_aaa_obj))
-test.fail_test(os.path.exists(work3_bbb_obj))
+    test.fail_test(os.path.exists(work3_aaa_obj))
+    test.fail_test(os.path.exists(work3_bbb_obj))
+
+    test.up_to_date(chdir = 'work3', options = opts, arguments = ".")
 
-test.up_to_date(chdir = 'work3', options = opts, arguments = ".")
 
 #
 test.pass_test()
diff --git a/test/implicit/IMPLICIT_COMMAND_DEPENDENCIES.py b/test/implicit/IMPLICIT_COMMAND_DEPENDENCIES.py
index 2431a61..bec2255 100644
--- a/test/implicit/IMPLICIT_COMMAND_DEPENDENCIES.py
+++ b/test/implicit/IMPLICIT_COMMAND_DEPENDENCIES.py
@@ -40,6 +40,8 @@ _python_ = TestSCons._python_
 
 test = TestSCons.TestSCons()
 
+test.write('file.in',     "file.in\n")
+
 generate_build_py_py_contents = """\
 #!%(python)s
 import os
@@ -61,17 +63,17 @@ os.chmod(sys.argv[1], 0o755)
 
 """
 
-extra = ''
-test.write('generate_build_py.py', generate_build_py_py_contents % locals())
-
+workpath = test.workpath()
 test.write('SConstruct', """
 DefaultEnvironment(tools=[])
 generate = Builder(action = r'%(_python_)s $GENERATE $TARGET')
-build = Builder(action = r'$BUILD_PY $TARGET $SOURCES')
+build = Builder(action = r'%(_python_)s $BUILD_PY $TARGET $SOURCES')
+cd_and_build = Builder(action = r'cd %(workpath)s && %(_python_)s $BUILD_PY $TARGET $SOURCES')
 env = Environment(tools=[],
                   BUILDERS = {
                         'GenerateBuild' : generate,
                         'BuildFile' : build,
+                        'CdAndBuildFile': cd_and_build,
                   },
                   GENERATE = 'generate_build_py.py',
                   BUILD_PY = 'build.py',
@@ -80,6 +82,8 @@ env.PrependENVPath('PATH', '.')
 env.PrependENVPath('PATHEXT', '.PY')
 env0        = env.Clone(IMPLICIT_COMMAND_DEPENDENCIES = 0)
 env1        = env.Clone(IMPLICIT_COMMAND_DEPENDENCIES = 1)
+env2        = env.Clone(IMPLICIT_COMMAND_DEPENDENCIES = 2)
+envAll      = env.Clone(IMPLICIT_COMMAND_DEPENDENCIES = 'all')
 envNone     = env.Clone(IMPLICIT_COMMAND_DEPENDENCIES = None)
 envFalse    = env.Clone(IMPLICIT_COMMAND_DEPENDENCIES = False)
 envTrue     = env.Clone(IMPLICIT_COMMAND_DEPENDENCIES = True)
@@ -90,44 +94,59 @@ AlwaysBuild(build_py)
 env.BuildFile('file.out',               'file.in')
 env0.BuildFile('file0.out',             'file.in')
 env1.BuildFile('file1.out',             'file.in')
+env2.BuildFile('file2.out',             'file.in')
+envAll.BuildFile('fileall.out',         'file.in')
 envNone.BuildFile('fileNone.out',       'file.in')
 envFalse.BuildFile('fileFalse.out',     'file.in')
 envTrue.BuildFile('fileTrue.out',       'file.in')
 envTrue.BuildFile('fileQuote.out',      'file.in', BUILD_PY='"build.py"')
-""" % locals())
-
 
+env1.CdAndBuildFile('cd_file1.out',     'file.in')
+env2.CdAndBuildFile('cd_file2.out',     'file.in')
+envAll.CdAndBuildFile('cd_fileall.out', 'file.in')
+""" % locals())
 
-test.write('file.in',     "file.in\n")
 
-test.run(arguments = '--tree=all .')
 
-expect_none = 'build.py %s file.in\nfile.in\n'
+def run_test(extra, python, _python_):
+    # Write the generate_build_py.py file. This uses the contents of the
+    # variable "extra" while writing build.py.
+    test.write('generate_build_py.py',
+               generate_build_py_py_contents % locals())
 
-test.must_match('file.out',         expect_none % 'file.out', mode='r')
-test.must_match('file0.out',        expect_none % 'file0.out', mode='r')
-test.must_match('file1.out',        expect_none % 'file1.out', mode='r')
-test.must_match('fileNone.out',     expect_none % 'fileNone.out', mode='r')
-test.must_match('fileFalse.out',    expect_none % 'fileFalse.out', mode='r')
-test.must_match('fileTrue.out',     expect_none % 'fileTrue.out', mode='r')
-test.must_match('fileQuote.out',    expect_none % 'fileQuote.out', mode='r')
+    # Run the SConscript file.
+    test.run(arguments = '--tree=all .')
 
+    # Generate some expected data of actions involving build.py. This expected
+    # data depends on the value of "extra".
+    build_none = 'build.py %s file.in\nfile.in\n'
+    build_extra = (build_none if not extra else
+        'build.py %s file.in\n{}file.in\n'.format(
+            extra.replace('\\\\n', '\n')))
+    build_extra_abs = '{} %s file.in\n{}file.in\n'.format(
+        test.workpath('build.py'),
+        extra.replace('\\\\n', '\n'))
 
+    empty_none = 'empty.py %s file.in\nfile.in\n'
 
-extra = 'xyzzy\\\\n'
-test.write('generate_build_py.py', generate_build_py_py_contents % locals())
+    # Verify that the output matches what is expected.
+    test.must_match('file.out',       build_none % 'file.out', mode='r')
+    test.must_match('file0.out',      build_none % 'file0.out', mode='r')
+    test.must_match('file1.out',      build_none % 'file1.out', mode='r')
+    test.must_match('file2.out',      build_extra % 'file2.out', mode='r')
+    test.must_match('fileall.out',    build_extra % 'fileall.out', mode='r')
+    test.must_match('fileNone.out',   build_none % 'fileNone.out', mode='r')
+    test.must_match('fileFalse.out',  build_none % 'fileFalse.out', mode='r')
+    test.must_match('fileTrue.out',   build_none % 'fileTrue.out', mode='r')
+    test.must_match('fileQuote.out',  build_none % 'fileQuote.out', mode='r')
+    test.must_match('cd_file1.out',   build_none % 'cd_file1.out', mode='r')
+    test.must_match('cd_file2.out',   build_extra % 'cd_file2.out', mode='r')
+    test.must_match('cd_fileall.out', build_extra % 'cd_fileall.out', mode='r')
 
-test.run(arguments = '--tree=all .')
 
-expect_extra = 'build.py %s file.in\nxyzzy\nfile.in\n'
+run_test('', python, _python_)
+run_test('xyzzy\\\\n', python, _python_)
 
-test.must_match('file.out',         expect_extra % 'file.out', mode='r')
-test.must_match('file0.out',        expect_none % 'file0.out', mode='r')
-test.must_match('file1.out',        expect_extra % 'file1.out', mode='r')
-test.must_match('fileNone.out',     expect_none % 'fileNone.out', mode='r')
-test.must_match('fileFalse.out',    expect_none % 'fileFalse.out', mode='r')
-test.must_match('fileTrue.out',     expect_extra % 'fileTrue.out', mode='r')
-test.must_match('fileQuote.out',    expect_extra % 'fileQuote.out', mode='r')
 
 
 test.pass_test()