fix(sdk): fix step logic when resuming runs with no metrics logged

[luisbergua]

Description

• Fixes WB-15093

What does the PR do?

When resuming a run, the step is incremented by 1 to avoid overwriting the last step. The problem is that, if the run didn't log any metrics, the step is still being increased by 1:

run = wandb.init(project='test_resume_step')
id = run.id
print('Final step:', run.step)
run.finish()

run = wandb.init(project='test_resume_step', resume='must', id=id)
print('Step after resuming:', run.step)
run.finish()

prints:

Final step: 0
Step after resuming: 1

This PR handles that specific case by checking if the summary contains any user-logged metrics and only increasing the step by 1 in that case. This is to avoid setting _step to 0 if only 1 step was logged as "_step" = n_steps - 1 so if n_steps=1 then _step will still be 0

🤖 Generated by Copilot at c9b9b9a

Fix a bug in SendManager that caused incorrect step increment when resuming a run with only system metrics. Update the logic for setting the resume state step in sender.py to check for user-defined data in the summary.

Testing

How was this PR tested? Checking different cases before and after the fix:

run = wandb.init(project='test_resume_step')
id = run.id
print('Final step:', run.step)
run.finish()

run = wandb.init(project='test_resume_step', resume='must', id=id)
print('Step after resuming:', run.step)
run.finish()

Before:

Final step: 0
Step after resuming: 1

After:

Final step: 0
Step after resuming: 0

---

run = wandb.init(project='test_resume_step')
id = run.id
run.log({'loss': 1})
print('Final step:', run.step)
run.finish()

run = wandb.init(project='test_resume_step', resume='must', id=id)
print('Step after resuming:', run.step)
run.finish()

Before:

Final step: 1
Step after resuming: 1

After:

Final step: 1
Step after resuming: 1

---

run = wandb.init(project='test_resume_step')
id = run.id
run.log({'loss': 1})
run.log({'loss': 2})
print('Final step:', run.step)
run.finish()

run = wandb.init(project='test_resume_step', resume='must', id=id)
print('Step after resuming:', run.step)
run.finish()

Before:

Final step: 2
Step after resuming: 2

After:

Final step: 2
Step after resuming: 2

🤖 Generated by Copilot at c9b9b9a

SendManager fixes
Resume state bug in metrics
Autumn leaves no trace

[codecov]

Codecov Report

Merging #6480 (c7ce691) into main (ed0922e) will decrease coverage by 0.07%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6480      +/-   ##
==========================================
- Coverage   77.03%   76.96%   -0.07%     
==========================================
  Files         389      389              
  Lines       45188    45190       +2     
==========================================
- Hits        34809    34780      -29     
- Misses      10326    10357      +31     
  Partials       53       53              

Flag	Coverage Δ
unittest	81.24% <100.00%> (-0.08%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
wandb/sdk/internal/sender.py	92.62% <100.00%> (+0.01%)	⬆️

... and 17 files with indirect coverage changes

[kptkin]

Awesome work!