Fix constraints generation when there are no differences

The new constraints generation implemented in #36158 had a bug that
constraint files have not been generated when there was no changes
(wrong file has been deleted). This resulted in PROD files generation
failing when there were no new releases to one of 670 dependencies.

This PR fixes it and improves the diagnostics of comstraints
generation:

* more information printed about generated files
* using shorten method wnen running commands (will add ellipsis if
  longer)
* failing when there are not constraints to upload - indicating
  a bug in the processs of constraints generation rather than when
  downloaded constraints are missing.

.github/actions/build-ci-images/action.yml

@@ -45,3 +45,4 @@ runs:
         name: source-constraints
         path: ./files/constraints-*/constraints-*.txt
         retention-days: 7
+        if-no-files-found: error

.github/workflows/ci.yml

@@ -536,6 +536,7 @@ jobs:
           name: constraints
           path: ./files/constraints-*/constraints-*.txt
           retention-days: 7
+          if-no-files-found: error
 
 
   static-checks:

dev/breeze/src/airflow_breeze/commands/release_management_commands.py

@@ -613,6 +613,7 @@ def run_generate_constraints(
         command="/opt/airflow/scripts/in_container/run_generate_constraints.py",
         output=output,
     )
+
     return (
         result.returncode,
         f"Constraints {shell_params.airflow_constraints_mode}:{shell_params.python}",
@@ -624,6 +625,15 @@ def run_generate_constraints(
 )
 
 
+def list_generated_constraints(output: Output | None):
+    get_console(output=output).print("\n[info]List of generated files in './files' folder:[/]\n")
+    found_files = Path("./files").rglob("*")
+    for file in sorted(found_files):
+        if file.is_file():
+            get_console(output=output).print(file.as_posix())
+    get_console(output=output).print()
+
+
 def run_generate_constraints_in_parallel(
     shell_params_list: list[ShellParams],
     python_version_list: list[str],
@@ -764,6 +774,7 @@ def generate_constraints(
         if return_code != 0:
             get_console().print(f"[error]There was an error when generating constraints: {info}[/]")
             sys.exit(return_code)
+    list_generated_constraints(output=None)
 
 
 SDIST_FILENAME_PREFIX = "apache-airflow-providers-"

scripts/in_container/in_container_utils.py

@@ -18,6 +18,7 @@
 
 import shlex
 import subprocess
+import textwrap
 from contextlib import contextmanager
 
 import rich_click as click
@@ -30,7 +31,7 @@
 @contextmanager
 def ci_group(group_name: str, github_actions: bool):
     if github_actions:
-        console.print(f"::group::{group_name[:200]}[/]", markup=False)
+        console.print(f"::group::{textwrap.shorten(group_name, width=200)}", markup=False)
     console.print(group_name, markup=False)
     try:
         yield

scripts/in_container/run_generate_constraints.py

@@ -154,16 +154,19 @@ def freeze_packages_to_file(config_params: ConfigParams, file: TextIO) -> None:
         check=True,
         capture_output=True,
     )
+    count_lines = 0
     for line in sorted(result.stdout.split("\n")):
         if line.startswith(("apache_airflow", "apache-airflow==", "/opt/airflow", "#", "-e")):
             continue
         if "@" in line:
             continue
         if line.strip() == "":
             continue
+        count_lines += 1
         file.write(line)
         file.write("\n")
-    console.print(f"[green]Constraints generated to file: {file.name}")
+    file.flush()
+    console.print(f"[green]Constraints generated to file: {file.name}. Wrote {count_lines} lines")
 
 
 def download_latest_constraint_file(config_params: ConfigParams):
@@ -201,8 +204,8 @@ def diff_constraints(config_params: ConfigParams) -> None:
     )
     if result.returncode == 0:
         console.print("[green]No changes in constraints files. exiting")
-        config_params.current_constraints_file.unlink(missing_ok=True)
-        sys.exit(0)
+        config_params.constraints_diff_file.unlink(missing_ok=True)
+        return
     result = run_command(
         [
             "diff",
@@ -444,6 +447,11 @@ def generate_constraints(
     else:
         console.print(f"[red]Unknown constraints mode: {airflow_constraints_mode}")
         sys.exit(1)
+    console.print("[green]Generated constraints:")
+    files = config_params.constraints_dir.rglob("*.txt")
+    for file in files:
+        console.print(file.as_posix())
+    console.print()
 
 
 if __name__ == "__main__":