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#
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# Copyright (C) 2016 Codethink Limited
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+# Copyright (C) 2019 Bloomberg L.P.
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#
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# This program is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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@@ -16,15 +17,37 @@ |
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#
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# Authors:
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# Tristan Van Berkom <tristan vanberkom codethink co uk>
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+# Daniel Silverstone <daniel silverstone codethink co uk>
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import re
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+import sys
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from ._exceptions import LoadError, LoadErrorReason
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from . import _yaml
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# Variables are allowed to have dashes here
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#
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-_VARIABLE_MATCH = r'\%\{([a-zA-Z][a-zA-Z0-9_-]*)\}'
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+PARSE_EXPANSION = re.compile(r"\%\{([a-zA-Z][a-zA-Z0-9_-]*)\}")
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+
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+
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+# Throughout this code you will see variables named things like `expstr`.
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+# These hold data structures called "expansion strings" and are the parsed
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+# form of the strings which are the input to this subsystem. Strings
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+# such as "Hello %{name}, how are you?" are parsed into the form:
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+# (3, ["Hello ", "name", ", how are you?"])
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+# i.e. a tuple of an integer and a list, where the integer is the cached
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+# length of the list, and the list consists of one or more strings.
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+# Strings in even indices of the list (0, 2, 4, etc) are constants which
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+# are copied into the output of the expansion algorithm. Strings in the
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+# odd indices (1, 3, 5, etc) are the names of further expansions to make.
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+# In the example above, first "Hello " is copied, then "name" is expanded
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+# and so must be another named expansion string passed in to the constructor
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+# of the Variables class, and whatever is yielded from the expansion of "name"
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+# is added to the concatenation for the result. Finally ", how are you?" is
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+# copied in and the whole lot concatenated for return.
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+#
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+# To see how strings are parsed, see `_parse_expstr()` after the class, and
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+# to see how expansion strings are expanded, see `_expand_expstr()` after that.
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# The Variables helper object will resolve the variable references in
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@@ -38,14 +61,15 @@ _VARIABLE_MATCH = r'\%\{([a-zA-Z][a-zA-Z0-9_-]*)\}' |
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# node (dict): A node loaded and composited with yaml tools
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#
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# Raises:
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-# LoadError, if unresolved variables occur.
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+# LoadError, if unresolved variables, or cycles in resolution, occur.
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#
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class Variables():
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def __init__(self, node):
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self.original = node
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- self.variables = self._resolve(node)
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+ self._expstr_map = self._resolve(node)
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+ self.flat = self._flatten()
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# subst():
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#
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@@ -61,139 +85,160 @@ class Variables(): |
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# LoadError, if the string contains unresolved variable references.
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#
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def subst(self, string):
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- substitute, unmatched, _ = self._subst(string, self.variables)
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- unmatched = list(set(unmatched))
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- if unmatched:
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- if len(unmatched) == 1:
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- message = "Unresolved variable '{var}'".format(var=unmatched[0])
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- else:
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- message = "Unresolved variables: "
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- for unmatch in unmatched:
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- if unmatched.index(unmatch) > 0:
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- message += ', '
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- message += unmatch
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-
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- raise LoadError(LoadErrorReason.UNRESOLVED_VARIABLE, message)
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-
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- return substitute
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-
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- def _subst(self, string, variables):
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-
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- def subst_callback(match):
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- nonlocal variables
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- nonlocal unmatched
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- nonlocal matched
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-
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- token = match.group(0)
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- varname = match.group(1)
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-
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- value = _yaml.node_get(variables, str, varname, default_value=None)
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- if value is not None:
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- # We have to check if the inner string has variables
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- # and return unmatches for those
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- unmatched += re.findall(_VARIABLE_MATCH, value)
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- matched += [varname]
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- else:
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- # Return unmodified token
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- unmatched += [varname]
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- value = token
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-
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- return value
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-
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- matched = []
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- unmatched = []
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- replacement = re.sub(_VARIABLE_MATCH, subst_callback, string)
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-
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- return (replacement, unmatched, matched)
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+ expstr = _parse_expstr(string)
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+
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+ try:
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+ return _expand_expstr(self._expstr_map, expstr)
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+ except KeyError:
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+ unmatched = []
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+
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+ # Look for any unmatched variable names in the expansion string
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+ for var in expstr[1][1::2]:
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+ if var not in self._expstr_map:
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+ unmatched.append(var)
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+
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+ if unmatched:
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+ message = "Unresolved variable{}: {}".format(
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+ "s" if len(unmatched) > 1 else "",
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+ ", ".join(unmatched)
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+ )
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+
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+ raise LoadError(LoadErrorReason.UNRESOLVED_VARIABLE, message)
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+ # Otherwise, re-raise the KeyError since it clearly came from some
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+ # other unknowable cause.
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+ raise
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# Variable resolving code
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#
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- # Here we substitute variables for values (resolve variables) repeatedly
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- # in a dictionary, each time creating a new dictionary until there is no
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- # more unresolved variables to resolve, or, until resolving further no
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- # longer resolves anything, in which case we throw an exception.
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+ # Here we resolve all of our inputs into a dictionary, ready for use
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+ # in subst()
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def _resolve(self, node):
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- variables = node
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-
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# Special case, if notparallel is specified in the variables for this
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# element, then override max-jobs to be 1.
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# Initialize it as a string as all variables are processed as strings.
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#
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- if _yaml.node_get(variables, bool, 'notparallel', default_value=False):
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- variables['max-jobs'] = str(1)
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-
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- # Resolve the dictionary once, reporting the new dictionary with things
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- # substituted in it, and reporting unmatched tokens.
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- #
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- def resolve_one(variables):
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- unmatched = []
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- resolved = {}
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-
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- for key, value in _yaml.node_items(variables):
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-
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- # Ensure stringness of the value before substitution
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- value = _yaml.node_get(variables, str, key)
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-
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- resolved_var, item_unmatched, matched = self._subst(value, variables)
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-
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- if _wrap_variable(key) in resolved_var:
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- referenced_through = find_recursive_variable(key, matched, variables)
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+ if _yaml.node_get(node, bool, 'notparallel', default_value=False):
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+ node['max-jobs'] = str(1)
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+
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+ ret = {}
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+ for key, value in _yaml.node_items(node):
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+ value = _yaml.node_get(node, str, key)
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+ ret[sys.intern(key)] = _parse_expstr(value)
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+ return ret
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+
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+ def _check_for_missing(self):
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+ # First the check for anything unresolvable
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+ summary = []
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+ for key, expstr in self._expstr_map.items():
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+ for var in expstr[1][1::2]:
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+ if var not in self._expstr_map:
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+ line = " unresolved variable '{unmatched}' in declaration of '{variable}' at: {provenance}"
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+ provenance = _yaml.node_get_provenance(self.original, key)
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+ summary.append(line.format(unmatched=var, variable=key, provenance=provenance))
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+ if summary:
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+ raise LoadError(LoadErrorReason.UNRESOLVED_VARIABLE,
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+ "Failed to resolve one or more variable:\n{}\n".format("\n".join(summary)))
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+
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+ def _check_for_cycles(self):
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+ # And now the cycle checks
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+ def cycle_check(expstr, visited, cleared):
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+ for var in expstr[1][1::2]:
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+ if var in cleared:
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+ continue
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+ if var in visited:
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raise LoadError(LoadErrorReason.RECURSIVE_VARIABLE,
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- "{}: ".format(_yaml.node_get_provenance(variables, key)) +
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+ "{}: ".format(_yaml.node_get_provenance(self.original, var)) +
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("Variable '{}' expands to contain a reference to itself. " +
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- "Perhaps '{}' contains '{}").format(key, referenced_through, _wrap_variable(key)))
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-
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- resolved[key] = resolved_var
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- unmatched += item_unmatched
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-
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- # Carry over provenance
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- resolved[_yaml.PROVENANCE_KEY] = variables[_yaml.PROVENANCE_KEY]
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- return (resolved, unmatched)
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-
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- # Resolve it until it's resolved or broken
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- #
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- resolved = variables
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- unmatched = ['dummy']
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- last_unmatched = ['dummy']
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- while unmatched:
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- resolved, unmatched = resolve_one(resolved)
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-
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- # Lists of strings can be compared like this
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- if unmatched == last_unmatched:
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- # We've got the same result twice without matching everything,
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- # something is undeclared or cyclic, compose a summary.
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- #
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- summary = ''
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- for unmatch in set(unmatched):
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- for var, provenance in self._find_references(unmatch):
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- line = " unresolved variable '{unmatched}' in declaration of '{variable}' at: {provenance}\n"
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- summary += line.format(unmatched=unmatch, variable=var, provenance=provenance)
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-
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- raise LoadError(LoadErrorReason.UNRESOLVED_VARIABLE,
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- "Failed to resolve one or more variable:\n{}".format(summary))
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-
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- last_unmatched = unmatched
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-
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- return resolved
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-
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- # Helper function to fetch information about the node referring to a variable
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+ "Perhaps '{}' contains '%{{{}}}").format(var, visited[-1], var))
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+ visited.append(var)
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+ cycle_check(self._expstr_map[var], visited, cleared)
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+ visited.pop()
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+ cleared.add(var)
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+
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+ cleared = set()
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+ for key, expstr in self._expstr_map.items():
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+ if key not in cleared:
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+ cycle_check(expstr, [key], cleared)
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+
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+ # _flatten():
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#
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- def _find_references(self, varname):
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- fullname = _wrap_variable(varname)
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- for key, value in _yaml.node_items(self.original):
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- if fullname in value:
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- provenance = _yaml.node_get_provenance(self.original, key)
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- yield (key, provenance)
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-
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-
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-def find_recursive_variable(variable, matched_variables, all_vars):
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- matched_values = (_yaml.node_get(all_vars, str, key) for key in matched_variables)
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- for key, value in zip(matched_variables, matched_values):
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- if _wrap_variable(variable) in value:
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- return key
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- # We failed to find a recursive variable
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- return None
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-
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-
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-def _wrap_variable(var):
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- return "%{" + var + "}"
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+ # Turn our dictionary of expansion strings into a flattened dict
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+ # so that we can run expansions faster in the future
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+ #
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+ # Raises:
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+ # LoadError, if the string contains unresolved variable references or
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+ # if cycles are detected in the variable references
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+ #
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+ def _flatten(self):
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+ flat = {}
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+ try:
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+ for key, expstr in self._expstr_map.items():
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+ if expstr[0] > 1:
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+ expstr = (1, [sys.intern(_expand_expstr(self._expstr_map, expstr))])
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+ self._expstr_map[key] = expstr
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+ flat[key] = expstr[1][0]
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+ except KeyError:
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+ self._check_for_missing()
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+ raise
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+ except RecursionError:
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+ self._check_for_cycles()
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+ raise
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+ return flat
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+
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+
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189
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+# Cache for the parsed expansion strings. While this is nominally
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+# something which might "waste" memory, in reality each of these
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+# will live as long as the element which uses it, which is the
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+# vast majority of the memory usage across the execution of BuildStream.
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+PARSE_CACHE = {
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+ # Prime the cache with the empty string since otherwise that can
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+ # cause issues with the parser, complications to which cause slowdown
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+ "": (1, [""]),
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+}
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+
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+
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200
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+# Helper to parse a string into an expansion string tuple, caching
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201
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+# the results so that future parse requests don't need to think about
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202
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+# the string
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203
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+def _parse_expstr(instr):
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+ try:
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+ return PARSE_CACHE[instr]
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206
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+ except KeyError:
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207
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+ # This use of the regex turns a string like "foo %{bar} baz" into
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+ # a list ["foo ", "bar", " baz"]
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209
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+ splits = PARSE_EXPANSION.split(instr)
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+ # If an expansion ends the string, we get an empty string on the end
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+ # which we can optimise away, making the expansion routines not need
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+ # a test for this.
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213
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+ if splits[-1] == '':
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+ splits = splits[:-1]
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+ # Cache an interned copy of this. We intern it to try and reduce the
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+ # memory impact of the cache. It seems odd to cache the list length
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+ # but this is measurably cheaper than calculating it each time during
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+ # string expansion.
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+ PARSE_CACHE[instr] = (len(splits), [sys.intern(s) for s in splits])
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+ return PARSE_CACHE[instr]
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+
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222
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+
|
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223
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+# Helper to expand a given top level expansion string tuple in the context
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224
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+# of the given dictionary of expansion strings.
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225
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+#
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226
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+# Note: Will raise KeyError if any expansion is missing
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227
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+def _expand_expstr(content, topvalue):
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228
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+ if topvalue[0] == 1:
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+ return topvalue[1][0]
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230
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+
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231
|
+ def __expand(value):
|
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232
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+ (expansion_len, expansion_bits) = value
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233
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+ idx = 0
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234
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+ while idx < expansion_len:
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235
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+ # First yield any constant string content
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236
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+ yield expansion_bits[idx]
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237
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+ idx += 1
|
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238
|
+ # Now, if there is an expansion variable left to expand, yield
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239
|
+ # the expansion of that variable too
|
|
240
|
+ if idx < expansion_len:
|
|
241
|
+ yield from __expand(content[expansion_bits[idx]])
|
|
242
|
+ idx += 1
|
|
243
|
+
|
|
244
|
+ return "".join(__expand(topvalue))
|