testing: add a new output writer and use it in t.Log

[suntala]

This is the first of two planned CLs. The first one introduces a new
output writer and uses it in a refactored implementation of t.Log.
This new writer maintains the formatting provided by t.Log while making
call site information optional. Additionally, it provides buffering of
input. The second CL would export a new t.Output method, refine its
implementation and add testing.

Co-authored-by: Aleks Fazlieva britishrum@users.noreply.github.com

For #59928.

[gopherbot]

This PR (HEAD: 59f309a) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/646956.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Gopher Robot:

Patch Set 1:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Arati:

Patch Set 1:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Arati:

Patch Set 2:

(2 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 2: Commit-Queue+1 Hold+1

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Go LUCI:

Patch Set 2:

Dry run: CV is trying the patch.

Bot data: {"action":"start","triggered_at":"2025-02-05T20:51:24Z","revision":"7e0a540201f0c62c2e98497ff9f853a2cfef293a"}

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 2: -Commit-Queue

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Go LUCI:

Patch Set 2:

This CL has failed the run. Reason:

Tryjob golang/try/gotip-linux-arm64-boringcrypto has failed with summary (view all results):

---

• go on master (change 646956)

Build or test failure, click here for results.

To reproduce, try gomote repro 8723741626891534561.

Additional links for debugging:

• Output for go tool dist test -json [shard 2]

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Go LUCI:

Patch Set 2: LUCI-TryBot-Result-1

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 2: Commit-Queue+1

(9 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Go LUCI:

Patch Set 2:

Dry run: CV is trying the patch.

Bot data: {"action":"start","triggered_at":"2025-02-05T21:19:36Z","revision":"7e0a540201f0c62c2e98497ff9f853a2cfef293a"}

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 2: -Commit-Queue

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Go LUCI:

Patch Set 2:

This CL has failed the run. Reason:

Tryjob golang/try/gotip-linux-arm64 has failed with summary (view all results):

---

• go on master (change 646956)

Build or test failure, click here for results.

To reproduce, try gomote repro 8723739851759057057.

Additional links for debugging:

• Output for go tool dist test -json [shard 1]

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 2:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 2:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: 8a61785) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/646956.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Arati:

Patch Set 3:

(5 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 3: Hold+1

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: 6fb1d3f) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/646956.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Arati:

Patch Set 4:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 4: Hold+1

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: 664f85f) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/646956.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Arati:

Patch Set 5:

(2 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: abff258) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/646956.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Arati:

Patch Set 6:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 6: Hold+1

(2 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Arati:

Patch Set 6:

(2 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: 9352f78) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/646956.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Arati:

Patch Set 7:

(2 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 7: Hold+1

(2 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Arati:

Patch Set 11:

(3 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: 99d2b80) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/646956.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Arati:

Patch Set 12:

(2 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 12: Hold+1

(7 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: fb1cfc5) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/646956.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Arati:

Patch Set 13:

(5 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Arati:

Patch Set 13:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: b0fed56) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/646956.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 14: -Hold

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Ian Lance Taylor:

Patch Set 14:

(6 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 14:

(4 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Ian Lance Taylor:

Patch Set 14:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: 5be3415) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/646956.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Arati:

Patch Set 15:

(9 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 15:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Ian Lance Taylor:

Patch Set 15:

(2 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: dc70f3e) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/646956.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Arati:

Patch Set 16:

(2 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Arati:

Patch Set 16:

(3 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Jonathan Amsterdam:

Patch Set 16:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/646956.
After addressing review feedback, remember to publish your drafts!