Add assertions of expected scenario results (#791)

Uses new metadata added in https://github.com/zanieb/packse/pull/61 to
assert that resolution succeeded or failed _and_ that the installed
package versions match the expected result.

scripts/scenarios/template.mustache

@@ -6,16 +6,48 @@
 /// GENERATED WITH `{{generated_with}}`
 /// SCENARIOS FROM `{{generated_from}}`
 
-
+use std::path::Path;
 use std::process::Command;
 
 use anyhow::Result;
+use assert_cmd::assert::Assert;
+use assert_cmd::prelude::*;
 use insta_cmd::_macro_support::insta;
 use insta_cmd::{assert_cmd_snapshot, get_cargo_bin};
 
 use common::{create_venv, BIN_NAME, INSTA_FILTERS};
 
 mod common;
+
+fn assert_command(venv: &Path, command: &str, temp_dir: &Path) -> Assert {
+    Command::new(venv.join("bin").join("python"))
+        .arg("-c")
+        .arg(command)
+        .current_dir(temp_dir)
+        .assert()
+}
+
+fn assert_installed(
+    venv: &Path,
+    package: &'static str,
+    version: &'static str,
+    temp_dir: &Path,
+) {
+    assert_command(
+        venv,
+        format!(
+            "import {package} as package; print(package.__version__, end='')"
+        )
+        .as_str(),
+        temp_dir,
+    )
+    .success()
+    .stdout(version);
+}
+
+fn assert_not_installed(venv: &Path, package: &'static str, temp_dir: &Path) {
+    assert_command(venv, format!("import {package}").as_str(), temp_dir).failure();
+}
 {{#scenarios}}
 
 /// {{name}}
@@ -46,6 +78,9 @@ fn {{normalized_name}}() -> Result<()> {
             {{#root.requires}}
             .arg("{{prefix}}-{{.}}")
             {{/root.requires}}
+            {{#environment.prereleases}}
+            .arg("--prerelease=allow")
+            {{/environment.prereleases}}
             .arg("--extra-index-url")
             .arg("https://test.pypi.org/simple")
             .arg("--cache-dir")
@@ -56,6 +91,25 @@ fn {{normalized_name}}() -> Result<()> {
         "###);
     });
 
+    {{#expected.explanation_lines}}
+    // {{.}}
+    {{/expected.explanation_lines}}
+    {{#expected.satisfiable}}
+    {{#expected.packages_list}}
+    assert_installed(
+        &venv,
+        "{{prefix_module}}_{{package_module}}",
+        "{{version}}",
+        &temp_dir
+    );
+    {{/expected.packages_list}}
+    {{/expected.satisfiable}}
+    {{^expected.satisfiable}}
+    {{#root.requires_packages}}
+    assert_not_installed(&venv, "{{prefix_module}}_{{package_module}}", &temp_dir);
+    {{/root.requires_packages}}
+    {{/expected.satisfiable}}
+
     Ok(())
 }
 {{/scenarios}}

scripts/scenarios/update.py

@@ -21,6 +21,7 @@ import shutil
 import subprocess
 import sys
 import textwrap
+import packaging.requirements
 from pathlib import Path
 
 
@@ -106,7 +107,7 @@ else:
     )
 
     if commit != PACKSE_COMMIT:
-        print("WARNING: Expected commit {PACKSE_COMMIT!r} but found {commit!r}.")
+        print(f"WARNING: Expected commit {PACKSE_COMMIT!r} but found {commit!r}.")
 
 print("Loading scenario metadata...", file=sys.stderr)
 data = json.loads(
@@ -137,6 +138,46 @@ for index, scenario in enumerate(data["scenarios"]):
 for scenario in data["scenarios"]:
     scenario["description_lines"] = textwrap.wrap(scenario["description"], width=80)
 
+
+# Wrap the expected explanation onto multiple lines
+for scenario in data["scenarios"]:
+    expected = scenario["expected"]
+    expected["explanation_lines"] = (
+        textwrap.wrap(expected["explanation"], width=80)
+        if expected["explanation"]
+        else []
+    )
+
+# Convert the expected packages into a list for rendering
+for scenario in data["scenarios"]:
+    expected = scenario["expected"]
+    expected["packages_list"] = []
+    for key, value in expected["packages"].items():
+        expected["packages_list"].append(
+            {
+                "package": key,
+                "version": value,
+                # Include a converted version of the package name to its Python module
+                "package_module": key.replace("-", "_"),
+            }
+        )
+
+
+# Convert the required packages into a list without versions
+for scenario in data["scenarios"]:
+    requires_packages = scenario["root"]["requires_packages"] = []
+    for requirement in scenario["root"]["requires"]:
+        package = packaging.requirements.Requirement(requirement).name
+        requires_packages.append(
+            {"package": package, "package_module": package.replace("-", "_")}
+        )
+
+
+# Include the Python module name of the prefix
+for scenario in data["scenarios"]:
+    scenario["prefix_module"] = scenario["prefix"].replace("-", "_")
+
+
 # Render the template
 print("Rendering template...", file=sys.stderr)
 output = chevron_blue.render(template=TEMPLATE.read_text(), data=data, no_escape=True)