Add deprecation warning for PhraseMatcher max_length

spacy/errors.py

@@ -48,6 +48,8 @@ class Warnings(object):
     W008 = ("Evaluating {obj}.similarity based on empty vectors.")
     W009 = ("Custom factory '{name}' provided by entry points of another "
             "package overwrites built-in factory.")
+    W010 = ("As of v2.1.0, the PhraseMatcher doesn't have a phrase length "
+            "limit anymore, so the max_length argument is now deprecated.")
 
 
 @add_codes
@@ -268,6 +270,8 @@ class Errors(object):
             "NBOR_RELOP.")
     E101 = ("NODE_NAME should be a new node and NBOR_NAME should already have "
             "have been declared in previous edges.")
+
+
 @add_codes
 class TempErrors(object):
     T001 = ("Max length currently 10 for phrase matching")

spacy/matcher.pyx

@@ -14,6 +14,7 @@ from .tokens.doc cimport Doc
 from .tokens.doc cimport get_token_attr
 from .attrs cimport ID, attr_id_t, NULL_ATTR
 from .errors import Errors, TempErrors
+from .errors import Errors, TempErrors, Warnings, deprecation_warning
 
 from .attrs import IDS
 from .attrs import FLAG61 as U_ENT
@@ -550,7 +551,8 @@ cdef class PhraseMatcher:
     cdef public object _patterns
 
     def __init__(self, Vocab vocab, max_length=0):
-        # TODO: Add deprecation warning on max_length
+        if max_length != 0:
+            deprecation_warning(Warnings.W010)
         self.mem = Pool()
         self.max_length = max_length
         self.vocab = vocab