Support missing versions being present and set in a local .python-version (#3134)

Requested in https://github.com/pyenv/pyenv/issues/2680
for deployments with a stock `.pyenv-version` that can use any
of a number of Python versions
and for compatibility with `uv`.

* Support `pyenv local --force`
* Support `pyenv-version-file-write --force`
* Support `pyenv version-name --force`
* Ignore missing versions when searching for executables
* Display "commmand not found" even when there are nonexistent versions

* exec.bats: replace `python` and `rspec` with something that doesn't exist globally, either
in Ubuntu Github CI, `python` exists globally

test/exec.bats

@@ -16,16 +16,22 @@ create_executable() {
 
 @test "fails with invalid version" {
   export PYENV_VERSION="3.4"
-  run pyenv-exec python -V
-  assert_failure "pyenv: version \`3.4' is not installed (set by PYENV_VERSION environment variable)"
+  run pyenv-exec nonexistent
+  assert_failure <<EOF
+pyenv: version \`3.4' is not installed (set by PYENV_VERSION environment variable)
+pyenv: nonexistent: command not found
+EOF
 }
 
 @test "fails with invalid version set from file" {
   mkdir -p "$PYENV_TEST_DIR"
   cd "$PYENV_TEST_DIR"
   echo 2.7 > .python-version
-  run pyenv-exec rspec
-  assert_failure "pyenv: version \`2.7' is not installed (set by $PWD/.python-version)"
+  run pyenv-exec nonexistent
+  assert_failure <<EOF
+pyenv: version \`2.7' is not installed (set by $PWD/.python-version)
+pyenv: nonexistent: command not found
+EOF
 }
 
 @test "completes with names of executables" {

test/local.bats

@@ -41,6 +41,18 @@ setup() {
   assert [ "$(cat .python-version)" = "1.2.3" ]
 }
 
+@test "fails to set a nonexistent local version" {
+  run pyenv-local 1.2.3
+  assert_failure "pyenv: version \`1.2.3' not installed"
+  assert [ ! -e .python-version ]
+}
+
+@test "sets a nonexistent local version with --force" {
+  run pyenv-local -f 1.2.3
+  assert_success ""
+  assert [ "$(cat .python-version)" = "1.2.3" ]
+}
+
 @test "changes local version" {
   echo "1.0-pre" > .python-version
   mkdir -p "${PYENV_ROOT}/versions/1.2.3"

test/version-file-write.bats

@@ -9,7 +9,7 @@ setup() {
 
 @test "invocation without 2 arguments prints usage" {
   run pyenv-version-file-write
-  assert_failure "Usage: pyenv version-file-write <file> <version>"
+  assert_failure "Usage: pyenv version-file-write [-f|--force] <file> <version> [...]"
   run pyenv-version-file-write "one" ""
   assert_failure
 }
@@ -21,6 +21,13 @@ setup() {
   assert [ ! -e ".python-version" ]
 }
 
+@test "setting nonexistent version succeeds with force" {
+  assert [ ! -e ".python-version" ]
+  run pyenv-version-file-write --force ".python-version" "2.7.6"
+  assert_success
+  assert [ -e ".python-version" ]
+}
+
 @test "writes value to arbitrary file" {
   mkdir -p "${PYENV_ROOT}/versions/2.7.6"
   assert [ ! -e "my-version" ]

test/version-name.bats

@@ -73,6 +73,11 @@ SH
   assert_failure "pyenv: version \`1.2' is not installed (set by PYENV_VERSION environment variable)"
 }
 
+@test "missing version with --force" {
+  PYENV_VERSION=1.2 run pyenv-version-name -f
+  assert_success "1.2"
+}
+
 @test "one missing version (second missing)" {
   create_version "3.5.1"
   PYENV_VERSION="3.5.1:1.2" run pyenv-version-name

test/which.bats

@@ -71,7 +71,16 @@ create_executable() {
 @test "version not installed" {
   create_executable "3.4" "py.test"
   PYENV_VERSION=3.3 run pyenv-which py.test
-  assert_failure "pyenv: version \`3.3' is not installed (set by PYENV_VERSION environment variable)"
+  assert_failure <<OUT
+pyenv: version \`3.3' is not installed (set by PYENV_VERSION environment variable)
+pyenv: py.test: command not found
+   
+The \`py.test' command exists in these Python versions:
+  3.4
+
+ Note: See 'pyenv help global' for tips on allowing both
+       python2 and python3 to be found.
+OUT
 }
 
 @test "versions not installed" {
@@ -80,6 +89,13 @@ create_executable() {
   assert_failure <<OUT
 pyenv: version \`2.7' is not installed (set by PYENV_VERSION environment variable)
 pyenv: version \`3.3' is not installed (set by PYENV_VERSION environment variable)
+pyenv: py.test: command not found
+   
+The \`py.test' command exists in these Python versions:
+  3.4
+
+ Note: See 'pyenv help global' for tips on allowing both
+       python2 and python3 to be found.
 OUT
 }