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fix Python 3.8 and 3.9 compatibility
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Walrus inside subscript (without parentheses) was added in Python 3.10.
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@Technologicat
Technologicat committed Sep 26, 2024
1 parent 26ed664 commit 49b772c
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Showing 3 changed files with 56 additions and 42 deletions.
9 changes: 7 additions & 2 deletions unpythonic/syntax/letdo.py
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Original file line number Diff line number Diff line change
Expand Up @@ -217,7 +217,7 @@ def dlet(tree, *, args, syntax, expander, **kw):
@dlet[x := 0]
def count():
(x := x + 1) # walrus requires parens here; or use `x << x + 1`
(x := x + 1)
return x
assert count() == 1
assert count() == 2
Expand Down Expand Up @@ -926,7 +926,12 @@ def _do0(tree):
raise SyntaxError("do0 body: expected a sequence of comma-separated expressions") # pragma: no cover
elts = tree.elts
# Use `local[]` and `do[]` as hygienically captured macros.
newelts = [q[a[_our_local][_do0_result := a[elts[0]]]], # noqa: F821, local[] defines it inside the do[].
#
# Python 3.8 and Python 3.9 require the parens around the walrus when used inside a subscript.
# TODO: Remove the parens when we bump minimum Python to 3.10.
# From https://docs.python.org/3/whatsnew/3.10.html:
# Assignment expressions can now be used unparenthesized within set literals and set comprehensions, as well as in sequence indexes (but not slices).
newelts = [q[a[_our_local][(_do0_result := a[elts[0]])]], # noqa: F821, local[] defines it inside the do[].
*elts[1:],
q[_do0_result]] # noqa: F821
return q[a[_our_do][t[newelts]]] # do0[] is also just a do[]
Expand Down
51 changes: 28 additions & 23 deletions unpythonic/syntax/tests/test_letdo.py
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,12 @@ def runtests():
# (including nested ``let`` constructs and similar).
# - No need for ``lambda e: ...`` wrappers. Inserted automatically,
# so the lines are only evaluated as the underlying seq.do() runs.
d1 = do[local[x := 17],
#
# Python 3.8 and Python 3.9 require the parens around the walrus when used inside a subscript.
# TODO: Remove the parens (in all walrus-inside-subscript instances in this file) when we bump minimum Python to 3.10.
# From https://docs.python.org/3/whatsnew/3.10.html:
# Assignment expressions can now be used unparenthesized within set literals and set comprehensions, as well as in sequence indexes (but not slices).
d1 = do[local[(x := 17)],
print(x),
x := 23,
x]
Expand All @@ -37,7 +42,7 @@ def runtests():

# v0.14.0: do[] now supports deleting previously defined local names with delete[]
a = 5
d = do[local[a := 17], # noqa: F841, yes, d is unused.
d = do[local[(a := 17)], # noqa: F841, yes, d is unused.
test[a == 17],
delete[a],
test[a == 5], # lexical scoping
Expand All @@ -46,7 +51,7 @@ def runtests():
test_raises[KeyError, do[delete[a], ], "should have complained about deleting nonexistent local 'a'"]

# do0[]: like do[], but return the value of the **first** expression
d2 = do0[local[y := 5], # noqa: F821, `local` defines the name on the LHS of the `<<`.
d2 = do0[local[(y := 5)], # noqa: F821, `local` defines the name on the LHS of the `<<`.
print("hi there, y =", y), # noqa: F821
42] # evaluated but not used
test[d2 == 5]
Expand Down Expand Up @@ -75,30 +80,30 @@ def runtests():
# Let macros. Lexical scoping supported.
with testset("let, letseq, letrec basic usage (new env-assignment syntax 0.15.3+)"):
# parallel binding, i.e. bindings don't see each other
test[let[x := 17,
y := 23][ # noqa: F821, `let` defines `y` here.
test[let[(x := 17),
(y := 23)][ # noqa: F821, `let` defines `y` here.
(x, y)] == (17, 23)] # noqa: F821

# sequential binding, i.e. Scheme/Racket let*
test[letseq[x := 1,
y := x + 1][ # noqa: F821
test[letseq[(x := 1),
(y := x + 1)][ # noqa: F821
(x, y)] == (1, 2)] # noqa: F821

test[letseq[x := 1,
x := x + 1][ # in a letseq, rebinding the same name is ok
test[letseq[(x := 1),
(x := x + 1)][ # in a letseq, rebinding the same name is ok
x] == 2]

# letrec sugars unpythonic.lispylet.letrec, removing the need for quotes on LHS
# and "lambda e: ..." wrappers on RHS (these are inserted by the macro):
test[letrec[evenp := (lambda x: (x == 0) or oddp(x - 1)), # noqa: F821, `letrec` defines `evenp` here.
oddp := (lambda x: (x != 0) and evenp(x - 1))][ # noqa: F821
test[letrec[(evenp := (lambda x: (x == 0) or oddp(x - 1))), # noqa: F821, `letrec` defines `evenp` here.
(oddp := (lambda x: (x != 0) and evenp(x - 1)))][ # noqa: F821
evenp(42)] is True] # noqa: F821

# nested letrecs work, too - each environment is internally named by a gensym
# so that outer ones "show through":
test[letrec[z := 9000][ # noqa: F821
letrec[evenp := (lambda x: (x == 0) or oddp(x - 1)), # noqa: F821
oddp := (lambda x: (x != 0) and evenp(x - 1))][ # noqa: F821
test[letrec[(z := 9000)][ # noqa: F821
letrec[(evenp := (lambda x: (x == 0) or oddp(x - 1))), # noqa: F821
(oddp := (lambda x: (x != 0) and evenp(x - 1)))][ # noqa: F821
(evenp(42), z)]] == (True, 9000)] # noqa: F821

with testset("let, letseq, letrec basic usage (previous modern env-assignment syntax)"):
Expand Down Expand Up @@ -151,8 +156,8 @@ def runtests():

# implicit do: an extra set of brackets denotes a multi-expr body
with testset("implicit do (extra bracket syntax for multi-expr let body) (new env-assignment syntax v0.15.3+)"):
a = let[x := 1,
y := 2][[ # noqa: F821
a = let[(x := 1),
(y := 2)][[ # noqa: F821
y := 1337, # noqa: F821
(x, y)]] # noqa: F821
test[a == (1, 1337)]
Expand All @@ -164,14 +169,14 @@ def runtests():
test[a == [1, 2]]

# implicit do works also in letseq, letrec
a = letseq[x := 1,
y := x + 1][[ # noqa: F821
a = letseq[(x := 1),
(y := x + 1)][[ # noqa: F821
x := 1337,
(x, y)]] # noqa: F821
test[a == (1337, 2)]

a = letrec[x := 1,
y := x + 1][[ # noqa: F821
a = letrec[(x := 1),
(y := x + 1)][[ # noqa: F821
x := 1337,
(x, y)]] # noqa: F821
test[a == (1337, 2)]
Expand Down Expand Up @@ -486,23 +491,23 @@ def test14():
x = "the nonlocal x" # restore the test environment

# v0.15.3+: walrus syntax
@dlet[x := "the env x"]
@dlet[(x := "the env x")]
def test15():
def inner():
(x := "updated env x") # noqa: F841, this writes to the let env since there is no `x` in an intervening scope, according to Python's standard rules.
inner()
return x
test[test15() == "updated env x"]

@dlet[x := "the env x"]
@dlet[(x := "the env x")]
def test16():
def inner():
x = "the inner x" # noqa: F841, unused on purpose, for testing. An assignment *statement* does NOT write to the let env.
inner()
return x
test[test16() == "the env x"]

@dlet[x := "the env x"]
@dlet[(x := "the env x")]
def test17():
x = "the local x" # This lexical variable shadows the env x.
def inner():
Expand Down
38 changes: 21 additions & 17 deletions unpythonic/syntax/tests/test_letdoutil.py
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Original file line number Diff line number Diff line change
Expand Up @@ -38,12 +38,16 @@ def validate(lst):
if type(k) is not Name:
return False # pragma: no cover, only reached if the test fails.
return True
# Python 3.8 and Python 3.9 require the parens around the walrus when used inside a subscript.
# TODO: Remove the parens (in all walrus-inside-subscript instances in this file) when we bump minimum Python to 3.10.
# From https://docs.python.org/3/whatsnew/3.10.html:
# Assignment expressions can now be used unparenthesized within set literals and set comprehensions, as well as in sequence indexes (but not slices).
test[validate(the[canonize_bindings(q[k0, v0].elts)])] # noqa: F821, it's quoted.
test[validate(the[canonize_bindings(q[((k0, v0),)].elts)])] # noqa: F821
test[validate(the[canonize_bindings(q[(k0, v0), (k1, v1)].elts)])] # noqa: F821
test[validate(the[canonize_bindings([q[k0 := v0]])])] # noqa: F821, it's quoted.
test[validate(the[canonize_bindings([q[(k0 := v0)]])])] # noqa: F821, it's quoted.
test[validate(the[canonize_bindings([q[k0 << v0]])])] # noqa: F821, it's quoted.
test[validate(the[canonize_bindings(q[k0 := v0, k1 := v1].elts)])] # noqa: F821, it's quoted.
test[validate(the[canonize_bindings(q[(k0 := v0), (k1 := v1)].elts)])] # noqa: F821, it's quoted.
test[validate(the[canonize_bindings(q[k0 << v0, k1 << v1].elts)])] # noqa: F821, it's quoted.

# --------------------------------------------------------------------------------
Expand All @@ -53,17 +57,17 @@ def validate(lst):
# need this utility, so we must test it first.
with testset("isenvassign"):
test[not isenvassign(q[x])] # noqa: F821
test[isenvassign(q[x := 42])] # noqa: F821
test[isenvassign(q[(x := 42)])] # noqa: F821
test[isenvassign(q[x << 42])] # noqa: F821

with testset("islet"):
test[not islet(q[x])] # noqa: F821
test[not islet(q[f()])] # noqa: F821

# unpythonic 0.15.3+, Python 3.8+
test[islet(the[expandrq[let[x := 21][2 * x]]]) == ("expanded_expr", "let")] # noqa: F821, `let` defines `x`
test[islet(the[expandrq[let[(x := 21)][2 * x]]]) == ("expanded_expr", "let")] # noqa: F821, `let` defines `x`
test[islet(the[expandrq[let[[x := 21] in 2 * x]]]) == ("expanded_expr", "let")] # noqa: F821
test[islet(the[expandrq[let[2 * x, where[x := 21]]]]) == ("expanded_expr", "let")] # noqa: F821
test[islet(the[expandrq[let[2 * x, where[(x := 21)]]]]) == ("expanded_expr", "let")] # noqa: F821

# unpythonic 0.15.0 to 0.15.2, previous modern notation for bindings
test[islet(the[expandrq[let[x << 21][2 * x]]]) == ("expanded_expr", "let")] # noqa: F821, `let` defines `x`
Expand Down Expand Up @@ -96,7 +100,7 @@ def f2():
return 2 * x # noqa: F821
test[islet(the[testdata[0].decorator_list[0]]) == ("expanded_decorator", "let")]

testdata = q[let[x := 21][2 * x]] # noqa: F821
testdata = q[let[(x := 21)][2 * x]] # noqa: F821
test[islet(the[testdata], expanded=False) == ("lispy_expr", "let")]

testdata = q[let[x << 21][2 * x]] # noqa: F821
Expand Down Expand Up @@ -196,7 +200,7 @@ def f5():
test[not isdo(q[f()])] # noqa: F821

# unpythonic 0.15.3+, Python 3.8+
test[isdo(the[expandrq[do[x := 21, # noqa: F821
test[isdo(the[expandrq[do[(x := 21), # noqa: F821
2 * x]]]) == "expanded"] # noqa: F821

test[isdo(the[expandrq[do[x << 21, # noqa: F821
Expand All @@ -210,16 +214,16 @@ def f5():
test[isdo(the[thedo]) == "curried"]

# unpythonic 0.15.3+, Python 3.8+
testdata = q[do[x := 21, # noqa: F821
testdata = q[do[(x := 21), # noqa: F821
2 * x]] # noqa: F821
test[isdo(the[testdata], expanded=False) == "do"]

testdata = q[do0[23, # noqa: F821
x := 21, # noqa: F821
(x := 21), # noqa: F821
2 * x]] # noqa: F821
test[isdo(the[testdata], expanded=False) == "do0"]

testdata = q[someothermacro[x := 21, # noqa: F821
testdata = q[someothermacro[(x := 21), # noqa: F821
2 * x]] # noqa: F821
test[not isdo(the[testdata], expanded=False)]

Expand All @@ -241,7 +245,7 @@ def f5():
# Destructuring - envassign

with testset("envassign destructuring (new env-assign syntax v0.15.3+)"):
testdata = q[x := 42] # noqa: F821
testdata = q[(x := 42)] # noqa: F821
view = UnexpandedEnvAssignView(testdata)

# read
Expand Down Expand Up @@ -316,7 +320,7 @@ def testletdestructuring(testdata):
test[unparse(view.body) == "(z * t)"]

# lispy expr
testdata = q[let[x := 21, y := 2][y * x]] # noqa: F821
testdata = q[let[(x := 21), (y := 2)][y * x]] # noqa: F821
testletdestructuring(testdata)
testdata = q[let[x << 21, y << 2][y * x]] # noqa: F821
testletdestructuring(testdata)
Expand Down Expand Up @@ -374,7 +378,7 @@ def testletdestructuring(testdata):
testletdestructuring(testdata)

# disembodied haskelly let-where (just the content, no macro invocation)
testdata = q[y * x, where[x := 21, y := 2]] # noqa: F821
testdata = q[y * x, where[(x := 21), (y := 2)]] # noqa: F821
testletdestructuring(testdata)
testdata = q[y * x, where[x << 21, y << 2]] # noqa: F821
testletdestructuring(testdata)
Expand Down Expand Up @@ -599,7 +603,7 @@ def f8():
# Destructuring - unexpanded do

with testset("do destructuring (unexpanded) (new env-assign syntax v0.15.3+)"):
testdata = q[do[local[x := 21], # noqa: F821
testdata = q[do[local[(x := 21)], # noqa: F821
2 * x]] # noqa: F821
view = UnexpandedDoView(testdata)
# read
Expand All @@ -611,11 +615,11 @@ def f8():
test[isenvassign(the[thing])]
# write
# This mutates the original, but we have to assign `view.body` to trigger the setter.
thebody[0] = q[local[x := 9001]] # noqa: F821
thebody[0] = q[local[(x := 9001)]] # noqa: F821
view.body = thebody

# implicit do, a.k.a. extra bracket syntax
testdata = q[let[[local[x := 21], # noqa: F821
testdata = q[let[[local[(x := 21)], # noqa: F821
2 * x]]] # noqa: F821
if sys.version_info >= (3, 9, 0): # Python 3.9+: the Index wrapper is gone.
theimplicitdo = testdata.slice
Expand All @@ -630,7 +634,7 @@ def f8():
thing = thebody[0].slice.value
test[isenvassign(the[thing])]
# write
thebody[0] = q[local[x := 9001]] # noqa: F821
thebody[0] = q[local[(x := 9001)]] # noqa: F821
view.body = thebody

test_raises[TypeError,
Expand Down

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